FN6859 Rev 4.00 Page 1 of 43
April 29, 2011
FN6859
Rev 4.00
April 29, 2011
ZL2008
Digital DC/DC Controller with Drivers and Pin-Strap Current Sharing
DATASHEET
The ZL2008 is a digital power controller with integrated
MOSFET drivers. Current sharing allows multiple devices to be
connected in parallel to source loads with very high current
demands. Adaptive performance optimization algorithms
improve power conversion efficiency. Zilker Labs Digital-DC™
technology enables a blend of power conversion performance
and power management features.
The ZL2008 is designed to be a flexible building block for DC
power and can be easily adapted to designs ranging from a
single-phase power supply operating from a 3.3V input to a
multi-phase supply operating from a 12V input. The ZL2008
eliminates the need for complicated power supply managers
as well as numerous external discrete components.
Key operating features can be configured by pin-straps,
including compensation, current sharing and output voltage.
The ZL2008 uses the I2C/SMBus™ with PMBus™ protocol for
communication with a host controller and the Digital-DC bus
for communication between Zilker Labs devices.
Applications
• Servers/storage equipment
• Telecom/datacom equipment
• Power supply modules
Features
Power Conversion
• Efficient synchronous buck controller
• Adaptive light load efficiency optimization
• 3V to 14V input range
• 0.54V to 5.5V output range (with margin)
• POLA and DOSA voltage trim modes
• ±1% output voltage accuracy
• Internal 3A MOSFET drivers
• Fast load transient response
• Current sharing and phase interleaving
•Snapshot™ parameter capture
• RoHS compliant (6mmx6mm) QFN package
Power Management
• Digital soft-start/stop
• Precision delay and ramp-up
•Power good/enable
• Voltage tracking, sequencing and margining
• Voltage, current and temperature monitoring
•I
2C/SMBus interface, PMBus compatible
• Output voltage and current protection
• Internal non-volatile memory (NVM)
Block Diagram
FIGURE 1. BLOCK DIAGRAM
Efficiency vs Load Current
FIGURE 2. EFFICIENCY vs LOAD CURRENT
CURRENT
SENSE
LDO
TEMP
SENSOR
V
SS
VTRK
MGN
VR VDD
BST
GH
SW
ISENA
ISENB
POWER
DRIVER
XTEMP
PWM
GL
I
2
C
SCL
SDA
SALRT
SA
MANAGEMENT
EN PG CFG UVLO
DLY ILIMFC
MONITOR
CONTROLLER
V25
SYNC
VSEN+
PGND SGND DGND
ADC
NON-
VOLATILE
MEMORY
DDC
VSEN-
Load Current (A)
Efficiency (%)
65
70
80
75
85
95
90
100
21406
4812
10
60
55
50
16 18 20
V
IN
= 12V
f
SW
= 400kHz
Circuit of Figure 4
V
OUT
= 3.3V
V
OUT
= 1.5V
NOT RECOMMENDED FOR NEW DESIGNS
RECOMMENDED REPLACEMENT PART
ZL6105
ZL2008
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April 29, 2011
Table of Contents
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Thermal Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Recommended Operating Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Electrical Specifications 4
Pin Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Pin Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical Application Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
ZL2008 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Digital-DC Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Power Conversion Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Power Management Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Multi-mode Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Power Conversion Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Internal Bias Regulators and Input Supply Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
High-side Driver Boost Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Start-up Procedure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Soft-start Delay and Ramp Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Power Good . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Switching Frequency and PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Power Train Component Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Current Limit Threshold Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Loop Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Non-linear Response (NLR) Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Efficiency Optimized Driver Dead-time Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Adaptive Diode Emulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Adaptive Frequency Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Power Management Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Input Undervoltage Lockout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Output Overvoltage Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Output Pre-Bias Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Output Overcurrent Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Thermal Overload Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Voltage Tracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Voltage Margining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
I2C/SMBus Communications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
I2C/SMBus Device Address Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Digital-DC Bus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Phase Spreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Output Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Fault Spreading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Temperature Monitoring Using the XTEMP Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Active Current Sharing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Phase Adding/Dropping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Monitoring via I2C/SMBus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Snapshot Parameter Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Non-Volatile Memory and Device Security Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Pin-strap Current Sharing Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
SMBus Address (SA0, SA1 Pins) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Current Share Pin-Straps (CFG0, CFG2 Pins) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
SYNC Clock (CFG1 Pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
ZL2008
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April 29, 2011
Soft-start (SS Pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Phase Enable (PH_EN Pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
MFR_CONFIG Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
VOUT_DROOP Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Current Sharing Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Ordering Information ..................................................................................................................................................................... 38
Related Tools and Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
About Intersil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Package Outline Drawing ................................................................................................................................................................ 43
ZL2008
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Absolute Maximum Ratings Thermal Information
DC Supply Voltage for VDD Pin . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 17V
MOSFET Drive Reference for VR Pin. . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5V
2.5V Logic Reference for V25 Pin . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 3V
Logic I/O Voltage for CFG(0, 1 ,2), DDC, EN, FC(0,1),
ILIM, MGN, PG, PH_EN, SA(0, 1), SALRT, SCL,
SDA, SS, SYNC, UVLO, V(0, 1) Pins . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6V
Analog Input Voltages for ISENB, VSEN, VTRK,
XTEMP Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5V
Analog Input Voltages for ISENA PIn . . . . . . . . . . . . . . . . . . . . -1.5V to 6.5V
High Side Supply Voltage for BST Pin . . . . . . . . . . . . . . . . . . . . -0.3V to 30V
Boost to Switch Voltage for BST -SW Pins . . . . . . . . . . . . . . . . . . -0.3V to 8V
High Side Drive Voltage for GH Pin. . . . . . . . . . . .(VSW-0.3V) to (VBST+0.3V)
Low Side Drive Voltage for GL Pin . . . . . . . . . . . (PGND-0.3V) to (VR+0.3V)
Switch Node Continuous for SW Pin . . . . . . . . . . . . . . .(PGND-0.3V) to 30V
Switch Node Transient (<100ns) for SW Pin . . . . . . . . . . (PGND-5V) to 30V
Ground Differential for DGND – SGND, PGND - SGND Pins . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 0.3V
ESD Rating
Human Body Model (Note 1, Tested per JESD22-A114E) . . . . . . . . . . . . . . . . .2kV
Machine Model (Tested per JESD22-A115-A) . . . . . . . . . . . . . . . . . 500V
Latch Up (Tested per JESD78). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100mA
Thermal Resistance (Typical) JA (°C/W) JC (°C/W)
36 Ld QFN (Notes 2, 3) . . . . . . . . . . . . . . . . 35 5
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-55°C to +150°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-55°C to +150°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Recommended Operating Conditions
Input Supply Voltage Range, VDD (See Figure 9)
VDD tied to VR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0V to 5.5V
VR floating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5V to 14V
Output Voltage Range, VOUT (Note 4) . . . . . . . . . . . . . . . . . . . . 0.54V to 5.5V
Operating Junction Temperature Range, TJ. . . . . . . . . . . . . . . . . . . -40°C to +125°C
Input Voltage
VIN, Rise Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5ms minimum
VIN Ramp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Monotonic
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product
reliability and result in failures not covered by warranty.
NOTES:
1. BST, SW pins rated at 1.5kV.
2. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech
Brief TB379.
3. For JC, the “case temp” location is the center of the exposed metal pad on the package underside.
4. Includes margin limits.
Electrical Specifications VDD = 12V, TA = -40°C to +85°C unless otherwise noted. Typical values are at TA = +25°C. Boldface limits apply
over the operating temperature range, -40°C to +85°C.
PARAMETER CONDITIONS
MIN
(Note 14) TYP
MAX
(Note 14) UNIT
Input and Supply Characteristics
IDD Supply Current at fSW = 200kHz GH, GL no load –16 30 mA
IDD Supply Current at fSW = 1.4MHz MISC_CONFIG[7] = 1 –25 50 mA
IDDS Shutdown Current EN = 0V
No I2C/SMBus activity
–6.5 9mA
Vr Reference Output Voltage VDD > 6V, IVR < 20mA 4.5 5.2 5.5 V
V25 Reference Output Voltage VR > 3V, IV25 < 20mA 2.25 2.5 2.75 V
Output Characteristics
Output Voltage Adjustment Range (Note 5) VIN > VOUT 0.6 –5.0 V
Output Voltage Set-point Resolution Set using resistors –10 –mV
Set using I2C/SMBus –±0.025 –% FS
(Note 6)
Output Voltage Accuracy (Note 7) Includes line, load, temp -1 –1%
Vsen Input Bias Current VSEN = 5.5V –110 200 µA
Current Sense Differential Input
Voltage (Ground Referenced)
VISENA -VISENB -100 –100 mV
Current Sense Differential Input Voltage (Vout
Referenced, Vout < 4.0V)
VISENA -VISENB -50 –50 mV
Current Sense Input Bias Current Ground referenced -100 –100 µA
ZL2008
FN6859 Rev 4.00 Page 5 of 43
April 29, 2011
Current Sense Input Bias Current
(Vout Referenced, Vout < 4.0V)
ISENA -1 –1µA
ISENB -100 –100 µA
Soft-start Delay Duration Range
(Note 8)
Set using SS pin or resistor 2–30 ms
Set using I2C/SMBus 0.002 –500 s
Soft-start Delay Duration Accuracy Turn-on delay (precise mode)
(Notes 8, 9, 10)
-±0.25 -ms
Turn-on delay (normal mode) (Note 10) --0.25/+4 -ms
Turn-off delay (Note 10) --0.25/+4 -ms
Soft-start Ramp Duration Range Set using SS pin or resistor 2–20 ms
Set using I2C0–200 ms
Soft-start Ramp Duration Accuracy –100 –µs
Logic Input/Output Characteristics
Logic Input Leakage Current EN, PG, SCL, SDA, SALRT pins -250 –250 nA
Logic Input Low, VIL ––0.8 V
Logic Input OPEN (N/C) Multi-mode logic pins –1.4 –V
Logic Input High, VIH 2.0 ––V
Logic Output Low, VOL IOL 4mA ––0.4 V
Logic Output High, VOH IOH -2mA 2.25 ––V
Oscillator and Switching Characteristics
Switching Frequency Range 200 –1400 kHz
Switching Frequency Set-point Accuracy Predefined settings (See Table 11) -5 –5%
Maximum Pwm Duty Cycle Factory default 95 ––%
Minimum Sync Pulse Width 150 ––ns
Input Clock Frequency Drift Tolerance External clock source -13 –13 %
Gate Drivers
High-side driver voltage (VBST -VSW)–4.5 –V
High-side Driver Peak Gate Drive
Current (Pull-down)
(VBST -VSW) = 4.5V 23–A
High-side Driver Pull-up Resistance (VBST -VSW) = 4.5V, (VBST -VGH) = 50mV –0.8 2
High-side Driver Pull-down Resistance (VBST -VSW) = 4.5V, (VGH -VSW) = 50mV –0.5 2
Low-side Driver Peak Gate
Drive Current (Pull-up)
VR = 5V –2.5 –A
Low-side Driver Peak Gate
Drive Current (Pull-down)
VR = 5V –1.8 –A
Low-side Driver Pull-up Resistance VR = 5V, (VR -VGL) = 50mV –1.2 2
Low-side Driver Pull-down Resistance VR = 5V, (VGL -PGND) = 50mV –0.5 2
Switching Timing
Gh Rise and Fall Time
Gl Rise and Fall Time
(VBST -VSW) = 4.5V, CLOAD = 2.2nF –520 ns
VR = 5V, CLOAD = 2.2nF –520 ns
Tracking
VTRK Input Bias Current VTRK = 5.5V –110 200 µA
VTRK Tracking Ramp Accuracy 100% Tracking, VOUT -VTRK -100 –+ 100 mV
VTRK Regulation Accuracy 100% Tracking, VOUT -VTRK -1 –1%
Electrical Specifications VDD = 12V, TA = -40°C to +85°C unless otherwise noted. Typical values are at TA = +25°C. Boldface limits apply
over the operating temperature range, -40°C to +85°C. (Continued)
PARAMETER CONDITIONS
MIN
(Note 14) TYP
MAX
(Note 14) UNIT
ZL2008
FN6859 Rev 4.00 Page 6 of 43
April 29, 2011
Fault Protection Characteristics
UVLO Threshold Range Configurable via I2C/SMBus 2.85 –16 V
UVLO Set-point Accuracy -150 –150 mV
UVLO Hysteresis Factory default –3–%
Configurable via I2C/SMBus 0–100 %
UVLO Delay ––2.5 µs
Power Good VOUT Threshold Factory default –90 –% VOUT
Power Good VOUT Hysteresis Factory default –5–%
Power Good Delay Using pin-strap or resistor (Note 11) 0–200 ms
Configurable via I2C/SMBus 0–500 s
VSEN Undervoltage Threshold Factory default –85 –% VOUT
Configurable via I2C/SMBus 0–110 % VOUT
VSEN Overvoltage Threshold Factory default –115 –% VOUT
Configurable via I2C/SMBus 0–115 % VOUT
VSEN Undervoltage Hysteresis –5–% VOUT
VSEN Undervoltage/Overvoltage
Fault Response Time
Factory default –16 –µs
Configurable via I2C/SMBus 5–60 µs
Current Limit Set-point Accuracy
(VOUT Referenced)
–±10 –% FS
(Note 12)
Current Limit Set-point Accuracy
(Ground Referenced)
–±10 –% FS
(Note 12)
Current Limit Protection Delay Factory default –5–tSW
(Note 13)
Configurable via I2C/SMBus 1–32 tSW
(Note 13)
Temperature Compensation of
Current Limit Protection Threshold
Factory default 4400 ppm/°C
Configurable via I2C/SMBus 100 12700
Thermal Protection Threshold
(Junction Temperature)
Factory default –125 –°C
Configurable via I2C/SMBus -40 –125 °C
Thermal Protection Hysteresis –15 –°C
NOTES:
5. Does not include margin limits.
6. Percentage of Full Scale (FS) with temperature compensation applied.
7. VOUT measured at the termination of the VSEN+ and VSEN-sense points.
8. The device requires a delay period following an enable signal and prior to ramping its output. Precise timing mode limits this delay period to approx
2ms, where in normal mode it may vary up to 4ms. Current Share member minimum delay is 5ms. Current share reference must be 10ms greater
than member delay.
9. Precise ramp timing mode is only valid when using EN pin to enable the device rather than PMBus enable.
10. The devices may require up to a 4ms delay following the assertion of the enable signal (normal mode) or following the de-assertion of the enable
signal.
11. Factory default Power Good delay is set to the same value as the soft-start ramp time.
12. Percentage of Full Scale (FS) with temperature compensation applied
13. tSW = 1/fSW, where fSW is the switching frequency.
14. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
15. Nominal capacitance of logic pins is 5pF.
Electrical Specifications VDD = 12V, TA = -40°C to +85°C unless otherwise noted. Typical values are at TA = +25°C. Boldface limits apply
over the operating temperature range, -40°C to +85°C. (Continued)
PARAMETER CONDITIONS
MIN
(Note 14) TYP
MAX
(Note 14) UNIT
ZL2008
FN6859 Rev 4.00 Page 7 of 43
April 29, 2011
Pin Configuration
ZL2008
(36 LD QFN)
TOP VIEW
SA1
ILIM
CFG0
SCL
SDA
SALRT
DGND
SA0
SYNC
36-Pin QFN
6 x 6 mm SW
PGND
GL
VR
ISENA
ISENB
VDD
GH
BST
EN
CFG1
MGN
DDC
XTEMP
V25
PG
PH_EN
CF G2
V1
UVLO
SS
VSEN+
VTRK
VSEN-
FC0
V0
FC1
Exposed Paddle
Connect to SGND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
27
26
25
24
23
22
21
20
19
36
35
34
33
32
31
30
29
28
Pin Descriptions
Pin Label
Type
(Note 16) Description
1 DGND PWR Digital ground. Common return for digital signals. Connect to low impedance ground plane.
2SYNC I/O, M
(Note 17)
Clock synchronization input. Used to set switching frequency of internal clock or for synchronization to external
frequency reference.
3 SA0 I, M Serial address select pins. Used to assign unique SMBus address to each IC or to enable certain management
features.
4SA1
5 ILIM I, M Current limit select. Sets the overcurrent threshold voltage for ISENA and ISENB.
6 CFG0 I, M Configuration pin. Used to setup current sharing and non-linear response.
7 SCL I/O Serial clock. Connect to external host and/or to other ZL devices.
8 SDA I/O Serial data. Connect to external host and/or to other ZL devices.
9 SALRT O Serial alert. Connect to external host if desired.
10 FC0 I Loop compensation configuration pins.
11 FC1
12 V0 I Output voltage selection pins. Used to set VOUT set-point and VOUT max.
13 V1
14 UVLO I, M Undervoltage lockout selection. Sets the minimum value for VDD voltage to enable VOUT.
15 SS I, M Soft-start pin. Sets the output voltage ramp time during turn-on and turn-off. Sets the delay from when EN is
asserted until the output voltage starts to ramp.
16 VTRK I Tracking sense input. Used to track an external voltage source.
17 VSEN+ I Output voltage feedback. Connect to output regulation point.
18 VSEN- I Output voltage feedback. Connect to load return or ground regulation point.
19 ISENB I Differential voltage input for current limit.
20 ISENA I Differential voltage input for current limit. High voltage tolerant.
ZL2008
FN6859 Rev 4.00 Page 8 of 43
April 29, 2011
21 VR PWR Internal 5V reference used to power internal drivers.
22 GL O Low side FET gate drive.
23 PGND PWR Power ground. Connect to low impedance ground plane.
24 SW PWR Drive train switch node.
25 GH O High-side FET gate drive.
26 BST PWR High-side drive boost voltage.
27 VDD
(Note 18)
PWR Supply voltage.
28 V25 PWR Internal 2.5V reference used to power internal circuitry.
29 XTEMP I External temperature sensor input. Connect to external 2N3904 diode connected transistor.
30 DDC I/O Digital-DC Bus. (Open Drain) Interoperability between Zilker Labs devices.
31 MGN I Signal that enables margining of output voltage.
32 CFG1 I, M Configuration pin. Used to setup clock synchronization and sequencing.
33 EN I Enable input (active high). Pull-up to enable PWM switching and pull-down to disable PWM switching.
34 PH_EN I Phase enable input (active high). Pull-up to enable phase and pull-down to disable phase for current sharing.
35 CFG2 I, M Configuration pin. Sets the phase offset (single-phase) or current sharing group position (multi-phase).
36 PG O Power good output.
ePad SGND PWR Exposed thermal pad. Common return for analog signals; internal connection to SGND. Connect to low
impedance ground plane.
NOTES:
16. I = Input, O = Output, PWR = Power or Ground. M = Multi-mode pins. Please refer to “Multi-mode Pins” on page 12.
17. The SYNC pin can be used as a logic pin, a clock input or a clock output.
18. VDD is measured internally and the value is used to modify the PWM loop gain.
Pin Descriptions (Continued)
Pin Label
Type
(Note 16) Description
ZL2008
FN6859 Rev 4.00 Page 9 of 43
April 29, 2011
Typical Application Circuit
The following application circuit represents a typical implementation of the ZL2008. For PMBus operation, it is recommended to tie the
enable pin (EN) to SGND.
ZL2008
1
35
34
33
32
31
30
29
28
10
11
12
13
14
15
16
17
18
2
3
4
5
6
7
8
9
27
26
25
24
23
22
21
20
19
36
DGND
SYNC
SA 0
SA 1
ILIM
CFG0
SCL
SDA
SALRT
FC0
FC1
V0
V1
UVLO
SS
VRTK
VSEN+
VDD
BST
GH
SW
PGND
GL
VR
ISENA
ISENB
PG
CFG2
PH_EN
EN
CFG1
MGN
DDC
XTE MP
V25
V
IN
10 µF
4 V
C
IN
3 x 10 µF
25 V
L
OUT
I
2
C/SMBus
2
POWER GOOD OU T PU T C
V25
DB
BAT54
CB
1 µF
16 V
QH
QL
2.2 µH
C
OUT
2 x 47 µF
6.3 V
4.7 µF
C
VR
6.3 V
V
OUT
RTN
SGND
EPAD
12V
V25
470 µF
2.5 V
POS - CAP
2*220 µF
6.3 V
100 m
VSEN-
ENABLE
F.B.1
Ground unification
4.7 µF
25 V
DDC B u s
3
Notes:
1. Ferrite bead is optional for input noise suppression
2. The I2C/SMBus requires pull -up resistors. Please refer to the I
2C/SMBus specifications for more details.
3. The DDC bus requires a pull-up resistor. The resistance will vary based on the capacitive loading of the bus (and on the number of devices
connected). The 10 k default value, assuming a maximum of 100 pF per device, provides the necessary 1 µs pull-up rise time. Please refer to the
DDC Bus section for more details.
PH ASE EN ABLE
FIGURE 3. 12V to 1.8V/16A Application Circuit
ZL2008
FN6859 Rev 4.00 Page 10 of 43
April 29, 2011
ZL2008 Overview
Digital-DC Architecture
The ZL2008 is an innovative mixed-signal power conversion and
power management IC based on Zilker Labs patented Digital-DC
technology that provides an integrated, high performance step-
down converter for a wide variety of power supply applications.
Today’s embedded power systems are typically designed for
optimal efficiency at maximum load, reducing the peak thermal
stress by limiting the total thermal dissipation inside the system.
Unfortunately, many of these systems are often operated at load
levels far below the peak where the power system has been
optimized, resulting in reduced efficiency. While this may not
cause thermal stress to occur, it does contribute to higher
electricity usage and results in higher overall system operating
costs.
Zilker Labs’ efficiency-adaptive ZL2008 DC/DC controller helps
mitigate this scenario by enabling the power converter to
automatically change their operating state to increase efficiency
and overall performance with little or no user interaction needed.
Its unique PWM loop utilizes an ideal mix of analog and digital
blocks to enable precise control of the entire power conversion
process with no software required, resulting in a very flexible
device that is also very easy to use. An extensive set of power
management functions are fully integrated and can be
configured using simple pin connections. The user configuration
can be saved in an internal non-volatile memory (NVM).
Additionally, all functions can be configured and monitored via
the SMBus hardware interface using standard PMBus
commands, allowing ultimate flexibility.
Once enabled, the ZL2008 is immediately ready to regulate
power and perform power management tasks with no
programming required. Advanced configuration options and real-
time configuration changes are available via the I2C/SMBus
interface if desired and continuous monitoring of multiple
operating parameters is possible with minimal interaction from a
host controller. Integrated sub-regulation circuitry enables single
supply operation from any supply between 3V and 14V with no
secondary bias supplies needed.
Digital
Compensator
I
2
C
NLR
Input Voltage Bus
V
OUT
BST
SW
D-PWM
+
-
VSEN+
SYNC
PLL
Power Management
TEMP
Sensor
MUX
XTEMP
CFG(0,1,2)MGN
EN
V(0,1)PG
SA(0,1)
SS
VR
SW
VSEN
ISENA
ILIM
VDD
MOSFET
Drivers
SYNC
GEN
VTRK
ISENB
VDD
SCL
SDA
SALRT
>
ADC
ADC
ADC
Communication
DACREFCN
FC(0,1)
DDC Voltage
Sensor VSEN-
NVM
Digital
Compensator
I
2
C
NLR
Input Voltage Bus
V
OUT
BST
SW
D-PWM
+
-
VSEN+
SYNC
PLL
Power Management
TEMP
Sensor
MUX
XTEMP
CFG(0,1,2)MGN
EN
V(0,1)PG
SA(0,1)
SS
VR
SW
VSEN
ISENA
ILIM
VDD
MOSFET
Drivers
SYNC
GEN
VTRK
ISENB
VDD
SCL
SDA
SALRT
>
ADC
ADC
ADC
Communication
DACREFCN
FC(0,1)
DDC Voltage
Sensor VSEN-
NVM
FIGURE 4. ZL2008 Block Diagram
ZL2008
FN6859 Rev 4.00 Page 11 of 43
April 29, 2011
Power Conversion Overview
The ZL2008 operates as a voltage-mode, synchronous buck
converter with a selectable constant frequency pulse width
modulator (PWM) control scheme that uses external MOSFETs,
capacitors, and an inductor to perform power conversion.
Figure 5 illustrates the basic synchronous buck converter
topology showing the primary power train components. This
converter is also called a step-down converter, as the output
voltage must always be lower than the input voltage. In its most
simple configuration, the ZL2008 requires two external N-
channel power MOSFETs, one for the top control MOSFET (QH)
and one for the bottom synchronous MOSFET (QL). The amount
of time that QH is on as a fraction of the total switching period is
known as the duty cycle D, which is described by Equation 1:
During time D, QH is on and VIN – VOUT is applied across the
inductor. The current ramps up as shown in Figure 6.
When QH turns off (time 1-D), the current flowing in the inductor
must continue to flow from the ground up through QL, during
which the current ramps down. Since the output capacitor COUT
exhibits a low impedance at the switching frequency, the AC
component of the inductor current is filtered from the output
voltage so the load sees nearly a DC voltage.
Typically, buck converters specify a maximum duty cycle that
effectively limits the maximum output voltage that can be
realized for a given input voltage. This duty cycle limit ensures
that the lowside MOSFET is allowed to turn on for a minimum
amount of time during each switching cycle, which enables the
bootstrap capacitor (CB in Figure 5) to be charged up and provide
adequate gate drive voltage for the high-side MOSFET. See
section“High-side Driver Boost Circuit” on page 12 for more
details.
In general, the size of components L1 and COUT as well as the
overall efficiency of the circuit are inversely proportional to the
switching frequency, fSW. Therefore, the highest efficiency circuit
may be realized by switching the MOSFETs at the lowest possible
frequency; however, this will result in the largest component size.
Conversely, the smallest possible footprint may be realized by
switching at the fastest possible frequency but this gives a
somewhat lower efficiency. Each user should determine the
optimal combination of size and efficiency when determining the
switching frequency for each application.
The block diagram for the ZL2008 is illustrated in Figure 4. In
this circuit, the target output voltage is regulated by connecting
the differential VSEN pins directly to the output regulation point.
The VSEN signal is then compared to a reference voltage that has
been set to the desired output voltage level by the user. The error
signal derived from this comparison is converted to a digital
value with a low-resolution, analog to digital (A/D) converter. The
digital signal is applied to an adjustable digital compensation
filter, and the compensated signal is used to derive the
appropriate PWM duty cycle for driving the external MOSFETs in a
way that produces the desired output.
The ZL2008 has several features to improve the power
conversion efficiency. A non-linear response (NLR) loop improves
the response time and reduces the output deviation as a result of
a load transient. The ZL2008 monitors the power converter’s
operating conditions and continuously adjusts the turn-on and
turn-off timing of the high-side and low-side MOSFETs to optimize
the overall efficiency of the power supply. Adaptive performance
optimization algorithms such as dead-time control, diode
emulation, and frequency control are available to provide greater
efficiency improvement.
Power Management Overview
The ZL2008 incorporates a wide range of configurable power
management features that are simple to implement with no
external components. Additionally, the ZL2008 includes circuit
protection features that continuously safeguard the device and
load from damage due to unexpected system faults. The ZL2008
can continuously monitor input voltage, output voltage/current,
internal temperature, and the temperature of an external
thermal diode. A Power Good output signal is also included to
enable power-on reset functionality for an external processor.
All power management functions can be configured using either
pin configuration techniques (see Figure 7) or via the I2C/SMBus
interface. Monitoring parameters can also be pre-configured to
provide alerts for specific conditions. See Application Note
AN2033 for more details on SMBus monitoring.
V
IN
V
OUT
GH
GL
ZL
SW
VR BST QH
QL
CB
DB
C
OUT
C
IN
FIGURE 5. Synchronous Buck Converter
IN
OUT
V
V
D
(EQ. 1)
Voltage
(V)
Time
Current (A)
V
IN
-V
OUT
0
-V
OUT
1 - D
I
O
IL
PK
IL
V
D
FIGURE 6. Inductor Waveform
ZL2008
FN6859 Rev 4.00 Page 12 of 43
April 29, 2011
Multi-mode Pins
In order to simplify circuit design, the ZL2008 incorporates
patented multi-mode pins that allow the user to easily configure
many aspects of the device with no programming. Most power
management features can be configured using these pins. The
multi-mode pins can respond to four different connections as
shown in Table 1. These pins are sampled when power is applied
or by issuing a PMBus Restore command (See Application Note
AN2033).
Pin-strap Settings: This is the simplest implementation method,
as no external components are required. Using this method, each
pin can take on one of three possible states: LOW, OPEN, or
HIGH. These pins can be connected to the V25 pin for logic HIGH
settings as this pin provides a regulated voltage higher than 2V.
Using a single pin, one of three settings can be selected. Using
two pins, one of nine settings can be selected.
Resistor Settings: This method allows a greater range of
adjustability when connecting a finite value resistor (in a
specified range) between the multi-mode pin and SGND.
Standard 1% resistor values are used, and only every fourth E96
resistor value is used so the device can reliably recognize the
value of resistance connected to the pin while eliminating the
error associated with the resistor accuracy. Up to 31 unique
selections are available using a single resistor.
I2C/SMBus Method: Almost any ZL2008 function can be
configured via the I2C/SMBus interface using standard PMBus
commands. Additionally, any value that has been configured
using the pin-strap or resistor setting methods can also be
re-configured and/or verified via the I2C/SMBus. See Application
Note AN2033 for more details.
The SMBus device address and VOUT_MAX are the only
parameters that must be set by external pins. All other device
parameters can be set via the I2C/SMBus. The device address is
set using the SA0 and SA1 pins. VOUT_MAX is determined as
10% greater than the voltage set by the V0 and V1 pins.
Power Conversion Functional
Description
Internal Bias Regulators and Input Supply
Connections
The ZL2008 employs two internal low dropout (LDO) regulators to
supply bias voltages for internal circuitry, allowing it to operate
from a single input supply. The internal bias regulators are as
follows:
VR: The VR LDO provides a regulated 5V bias supply for the
MOSFET driver circuits. It is powered from the VDD pin. A 4.7µF
filter capacitor is required at the VR pin.
V25: The V25 LDO provides a regulated 2.5V bias supply for the
main controller circuitry. It is powered from an internal 5V node.
A 10µF filter capacitor is required at the V25 pin.
When the input supply (VDD) is higher than 5.5V, the VR pin
should not be connected to any other pins. It should only have a
filter capacitor attached as shown in Figure 8. Due to the dropout
voltage associated with the VR bias regulator, the VDD pin must
be connected to the VR pin for designs operating from a supply
below 5.5V. Figure 8 illustrates the required connections for both
cases.
Note: the internal bias regulators are not designed to be outputs
for powering other circuitry. Do not attach external loads to any of
these pins. The multi-mode pins may be connected to the V25
pin for logic HIGH settings.
High-side Driver Boost Circuit
The gate drive voltage for the high-side MOSFET driver is
generated by a floating bootstrap capacitor, CB (see Figure 5).
When the lower MOSFET (QL) is turned on, the SW node is pulled
to ground and the capacitor is charged from the internal VR bias
regulator through diode DB. When QL turns off and the upper
MOSFET (QH) turns on, the SW node is pulled up to VDD and the
voltage on the bootstrap capacitor is boosted approximately 5V
above VDD to provide the necessary voltage to power the
high-side driver. A Schottky diode should be used for DB to help
maximize the high-side drive supply voltage.
TABLE 1. Multi-mode Pin Configuration
Pin Tied To Value
LOW
(Logic LOW)
< 0.8VDC
OPEN
(N/C)
No connection
HIGH
(Logic HIGH)
> 2.0VDC
Resistor to SGND Set by resistor value
ZL
Multi-mode Pin
ZL
R
SET
Logic
high
Logic
low
Open
Pin-strap
Settings
Resistor
Settings
Multi-mode Pin
FIGURE 7. Pin-strap and Resistor Setting Examples
VIN
VDD
VR
ZL
VIN
VDD
VR
ZL
3V ≤VIN ≤ 5.5V 5.5V <VIN ≤ 14V
FIGURE 8. Input Supply Connections
ZL2008
FN6859 Rev 4.00 Page 13 of 43
April 29, 2011
Output Voltage Selection
STANDARD MODE
The output voltage may be set to any voltage between 0.6V and
5.0V provided that the input voltage is higher than the desired
output voltage by an amount sufficient to prevent the device
from exceeding its maximum duty cycle specification. Using the
pin-strap method, VOUT can be set to any of nine standard
voltages as shown in Table 2.
The resistor setting method can be used to set the output voltage
to levels not available in Table 2. Resistors R0 and R1 are
selected to produce a specific voltage between 0.6V and 5.0V in
10mV steps. Resistor R1 provides a coarse setting and resistor
R0 provides a fine adjustment, thus eliminating the additional
errors associated with using two 1% resistors (this typically adds
approx 1.4% error).
To set VOUT using resistors, follow the steps below to calculate an
index value and then use Table 3 to select the resistor that
corresponds to the calculated index value as follows:
1. Calculate Index1:
Index1 = 4 x VOUT (VOUT in 10mV steps)
2. Round the result down to the nearest whole number.
3. Select the value of R1 from Table 3 using the Index1 rounded
value from step 2.
4. Calculate Index0:
5. Index0 = 100 x VOUT – (25 x Index1)
6. Select the value of R0 from Table 3 using the Index0 value
from Step 4. Example from Figure 9: For VOUT = 1.33V,
Index1 = 4 x 1.33V = 5.32;
From Table 3, R1 = 16.2k
Index0 = (100 x 1.33V) – (25 x 5) = 8;
From Table 3, R0 = 21.5k
SMBUS MODE
The output voltage may be set to any value between 0.6V and
5.0V using a PMBus command over the I2C/SMBus interface.
See Application Note AN2033 for details.
TABLE 2. Output Voltage Pin-strap Settings
V0
LOW
(V)
OPEN
(V)
HIGH
(V)
V1
LOW 0.6 0.8 1.0
OPEN 1.2 1.5 1.8
HIGH 2.5 3.3 5.0
TABLE 3. Output Voltage Resistors Settings
Index
R0 or R1
(k)
010
1 11
2 12.1
3 13.3
4 14.7
5 16.2
617.8
7 19.6
821.5
9 23.7
10 26.1
11 28.7
12 31.6
13 34.8
14 38.3
15 42.2
16 46.4
17 51.1
18 56.2
19 61.9
20 68.1
21 75
22 82.5
23 90.9
24 100
ZL2008
FN6859 Rev 4.00 Page 14 of 43
April 29, 2011
POLA VOLTAGE TRIM MODE
The output voltage mapping can be changed to match the
voltage setting equations for POLA and DOSA standard modules.
The standard method for adjusting the output voltage for a POLA
module is defined by Equation 2:
The resistor, RSET, is external to the POLA module. See Figure 10.
To stay compatible with this existing method for adjusting the
output voltage and to keep the same external RSET resistor when
using the ZL2008, the module manufacturer should add a 10k
resistor on the module as shown in Figure 11. Now, the same
RSET used for an analog POLA module will provide the same
output voltage when using a digital POLA module based on the
ZL2008.
The POLA mode is activated through pin-strap by connecting a
110k resistor on V0 to SGND. The V1 pin is then used to adjust
the output voltage as shown in Table 4.
The POLA mode can also be activated through PMBus
commands. See Application Note AN2033 for more details.
V
IN
V
OUT
1.33V
GH
GL
ZL
SW
V0
R0
21. 5 kΩ
V1
R1
16 .2 kΩ
FIGURE 9. Output Voltage Resistor Setting Example
k
VV V
kR
OUT
SET 43.1
69.0
69.0
10
(EQ. 2)
-
+
1.43kΩ
Rset
0.69V
10kΩ
V
OUT
POLA Module
FIGURE 10. Output Voltage Setting on POLA Module
TABLE 4. POLA Mode VOUT Settings
VOUT
(V)
RSET (k)
In series with 10k resistor
0.700 162
0.752 110
0.758 100
0.765 90.9
0.772 82.5
0.790 75.0
0.800 56.2
0.821 51.1
0.834 46.4
0.848 42.2
0.880 34.8
0.899 31.6
0.919 28.7
0.965 23.7
0.991 21.5
1.000 19.6
1.100 16.2
1.158 13.3
1.200 12.1
1.250 9.09
1.500 7.50
1.669 5.62
1.800 4.64
2.295 2.87
2.506 2.37
3.300 1.21
5.000 0.162
NOTE: (R0 = 110k, R1 = RSET + 10k)
ZL
10 kΩ
POLA
MODULE
Rset
V1
V0
110 kΩ
FIGURE 11. RSET on a POLA Module
ZL2008
FN6859 Rev 4.00 Page 15 of 43
April 29, 2011
DOSA VOLTAGE TRIM MODE
On a DOSA module, the VOUT setting follows Equation 3:
To maintain DOSA compatibility, the same scheme is used as with a
POLA module except the 10k resistor is replaced with a 8.66k
resistor as shown in Figure 12.
The DOSA mode VOUT settings are listed in Table 5.
Start-up Procedure
The ZL2008 follows a specific internal start-up procedure after
power is applied to the VDD pin. Table 6 describes the start-up
sequence.
If the device is to be synchronized to an external clock source, the
clock frequency must be stable prior to asserting the EN pin. The
device requires approximately 5ms to 10ms to check for specific
values stored in its internal memory. If the user has stored values
in memory, those values will be loaded. The device will then
check the status of all multi-mode pins and load the values
associated with the pin settings.
Once this process is completed, the device is ready to accept
commands via the I2C/SMBus interface and the device is ready
to be enabled. Once enabled, the device requires approximately
2ms before its output voltage may be allowed to start its ramp-
up process. If a soft-start delay period less than 2ms has been
configured (using PMBus commands), the device will default to a
2ms delay period. If a delay period greater than 2ms is
configured, the device will wait for the configured delay period
prior to starting to ramp its output.
After the delay period has expired, the output will begin to ramp
towards its target voltage according to the pre-configured
soft-start ramp time that has been set using the SS pin. It should
be noted that if the EN pin is tied to VDD, the device will still
require approx 5ms to 10ms before the output can begin its
ramp-up as described in Table 6.
Soft-start Delay and Ramp Times
It may be necessary to set a delay from when an enable signal is
received until the output voltage starts to ramp to its target
value. In addition, the designer may wish to precisely set the time
required for VOUT to ramp to its target value after the delay period
has expired. These features may be used as part of an overall
inrush current management strategy or to precisely control how
fast a load IC is turned on. The ZL2008 gives the system designer
several options for precisely and independently controlling both
the delay and ramp time periods.
The soft-start delay period begins when the EN pin is asserted
and ends when the delay time expires. The soft-start delay period
is set using the SS pin. Precise ramp delay timing reduces the
delay time variations but is only available when the appropriate
bit in the MISC_CONFIG register has been set. Please refer to
Application Note AN2033 for details.
The soft-start ramp timer enables a precisely controlled ramp to
the nominal VOUT value that begins once the delay period has
expired. The ramp-up is guaranteed monotonic and its slope may
be precisely set using the SS pin.
The soft-start delay and ramp times can be set to standard
values according to Table 7.
TABLE 5. DOSA Mode VOUT Settings
VOUT
(V)
RSET (k)
In series with 8.660k resistor
0.700 162
0.752 113
0.758 100
0.765 90.9
0.772 82.5
0.790 75.0
0.800 57.6
0.821 52.3
0.834 47.5
0.848 43.2
0.880 36.5
0.899 33.2
0.919 30.1
0.965 25.5
0.991 22.6
1.000 21.0
1.100 17.8
1.158 14.7
1.200 13.3
1.250 10.5
1.500 8.87
1.669 6.98
1.800 6.04
2.295 4.32
2.506 3.74
3.300 2.61
5.000 1.50
NOTE: (R0 = 110k, R1 = RSET + 8.66k)
VV
R
OUT
SET 69.0
6900
(EQ. 3)
ZL
8.66 kΩ
DOSA
MODULE
Rset
V1
V0
110 kΩ
FIGURE 12. RSET on a DOSA Module
ZL2008
FN6859 Rev 4.00 Page 16 of 43
April 29, 2011
If the desired soft-start delay and ramp times are not one of the
values listed in Table 7, the times can be set to a custom value by
connecting a resistor from the SS pin to SGND using the
appropriate resistor value from Table 8. The value of this resistor
is measured upon start-up or Restore and will not change if the
resistor is varied after power has been applied to the ZL2008.
See Figure 13 for typical connections using resistors.
The soft-start delay and ramp times can also be set to custom
values via the I2C/SMBus interface. When the SS delay time is
set to 0ms, the device will begin its ramp-up after the internal
circuitry has initialized (approx. 2ms). When the soft-start ramp
period is set to 0ms, the output will ramp up as quickly as the
output load capacitance and loop settings will allow. It is
generally recommended to set the soft-start ramp to a value
greater than 500µs to prevent inadvertent fault conditions due to
excessive inrush current.
Power Good
The ZL2008 provides a Power Good (PG) signal that indicates the
output voltage is within a specified tolerance of its target level
and no fault condition exists. By default, the PG pin will assert if
the output is within
-10% of the target voltage. These limits and the polarity of the pin
may be changed via the I2C/SMBus interface. See Application
Note AN2033 for details.
A PG delay period is defined as the time from when all conditions
within the ZL2008 for asserting PG are met to when the PG pin is
actually asserted. This feature is commonly used instead of using
an external reset controller to control external digital logic. By
default, the ZL2008 PG delay is set equal to the soft-start ramp
time setting. Therefore, if the soft-start ramp time is set to 10ms,
the PG delay will be set to 10ms. The PG delay may be set
independently of the soft-start ramp using the I2C/SMBus as
described in Application Note AN2033.
TABLE 6. ZL2106 START-UP SEQUENCE
STEP # STEP NAME DESCRIPTION TIME DURATION
1 Power Applied Input voltage is applied to the ZL2008’s VDD pin Depends on input supply ramp
time
2 Internal Memory Check The device will check for values stored in its internal memory. This step
is also performed after a Restore command.
Approx 5ms to 10ms (device will
ignore an enable signal or PMBus
traffic during this period)
3 Multi-mode Pin Check The device loads values configured by the multi-mode pins.
4 Device Ready The device is ready to accept an enable signal. -
5 Pre-ramp Delay The device requires approximately 2ms following an enable signal and
prior to ramping its output. Additional pre-ramp delay may be
configured using the SS pin.
Approximately 2ms
TABLE 7. Soft-start Pin-strap Settings
SS Pin
Delay Time
(ms)
Ramp Time
(ms)
LOW 2 2
OPEN 5 5
HIGH 10 10
ZL
SS
R
SS
FIGURE 13. SS Pin Resistor Connections
TABLE 8. SS Resistor Settings
RSS
(k)
Delay Time
(ms)
Ramp Time
(ms)
10
2
5
11 10
12.1 20
13.3
5
2
14.7 5
16.2 10
17.8 20
19.6
10
2
21.5 5
23.7 10
26.1 20
28.7
15
2
31.6 5
34.8 10
38.3 20
42.2
20
2
46.4 5
51.1 10
56.2 20
61.9
30
2
68.1 5
75 10
82.5 20
ZL2008
FN6859 Rev 4.00 Page 17 of 43
April 29, 2011
Switching Frequency and PLL
The ZL2008 incorporates an internal phase-locked loop (PLL) to
clock the internal circuitry. The PLL can be driven by an external
clock source connected to the SYNC pin. When using the internal
oscillator, the SYNC pin can be configured as a clock source for
other Zilker Labs devices.
The SYNC pin is a unique pin that can perform multiple functions
depending on how it is configured. The CFG1 pin is used to select
the operating mode of the SYNC pin as shown in Table 9.
Figure 14 illustrates the typical connections for each mode.
Configuration A: SYNC OUTPUT
When the SYNC pin is configured as an output (CFG1 pin is tied
HIGH), the device will run from its internal oscillator and will drive the
resulting internal oscillator signal (preset to 400kHz) onto the SYNC
pin so other devices can be synchronized to it. The SYNC pin will not
be checked for an incoming clock signal while in this mode.
Configuration B: SYNC INPUT
When the SYNC pin is configured as an input (CFG1 pin is tied
LOW), the device will automatically check for a clock signal on
the SYNC pin each time EN is asserted. The ZL2008’s oscillator
will then synchronize with the rising edge of the external clock.
The incoming clock signal must be in the range of 200kHz to
1.4MHz and must be stable when the enable pin is asserted. The
clock signal must also exhibit the necessary performance
requirements (see “Electrical Specifications” on page 4). In the
event of a loss of the external clock signal, the output voltage
may show transient over/undershoot.
If this happens, the ZL2008 will automatically switch to its
internal oscillator and switch at a frequency close to the previous
incoming frequency.
Configuration C: SYNC AUTO DETECT
When the SYNC pin is configured in auto detect mode (CFG1 pin
is left OPEN), the device will automatically check for a clock
signal on the SYNC pin after enable is asserted.
If a clock signal is present, The ZL2008’s oscillator will then
synchronize the rising edge of the external clock. Refer to SYNC
INPUT description.
If no incoming clock signal is present, the ZL2008 will configure
the switching frequency according to the state of the SYNC pin as
listed in Table 10. In this mode, the ZL2008 will only read the
SYNC pin connection during the start-up sequence. Changes to
SYNC pin connections will not affect fSW until the power (VDD) is
cycled off and on.
If the user wishes to run the ZL2008 at a frequency not listed in
Table 10, the switching frequency can be set using an external
resistor, RSYNC, connected between SYNC and SGND using Table 11.
TABLE 9. SYNC Pin Function Selection
CFG1 Pin SYNC Pin Function
LOW SYNC is configured as an input
OPEN Auto Detect mode
HIGH SYNC is configured as an output
fSW = 400kHz
TABLE 10. Switching Frequency Pin-strap Setting
SYNC Pin Frequency
LOW 200kHz
OPEN 400kHz
HIGH 1MHz
Resistor See Table 11
ZL
Logic
high
CFG1
SYNC
200 kHz – 1.33MHz
ZL
CFG1
SYNC
200kHz – 1.4MHz
ZL
N/ C
CFG1
SYNC
200kHz – 1.4MHz
A) SYNC = output B) SYNC = input
ZL
N/ C
CFG1
SYNC
ZL
R
SYN C
N/ C
CFG1
SYNC
Logic
high
Logic
low
Open
C) SYNC = Auto Detect
OR OR
FIGURE 14. Sync Pin Configurations
ZL2008
FN6859 Rev 4.00 Page 18 of 43
April 29, 2011
The switching frequency can also be set to any value between
200kHz and 1.33MHz using the I2C/SMBus interface. The
available frequencies below 1.4MHz are defined by fSW =8MHz/N,
where the whole number N is 6 N 40. See Application Note
AN2033 for details.
If a value other than fSW = 8MHz/N is entered using a PMBus
command, the internal circuitry will select the valid switching
frequency value that is closest to the entered value. For example,
if 810kHz is entered, the device will select 800kHz (N=10).
When multiple Zilker Labs devices are used together, connecting
the SYNC pins together will force all devices to synchronize with
each other. The CFG1 pin of one device must set its SYNC pin as
an output and the remaining devices must have their SYNC pins
set as Auto Detect.
Note: The switching frequency read back using the appropriate
PMBus command will differ slightly from the selected values in
Table 11. The difference is due to hardware quantization.
Power Train Component Selection
The ZL2008 is a synchronous buck converter that uses external
MOSFETs, inductor and capacitors to perform the power
conversion process. The proper selection of the external
components is critical for optimized performance.
To select the appropriate external components for the desired
performance goals, the power supply requirements listed in
Table 12 must be known.
DESIGN GOAL TRADE-OFFS
The design of the buck power stage requires several
compromises among size, efficiency, and cost. The inductor core
loss increases with frequency, so there is a trade-off between a
small output filter made possible by a higher switching frequency
and getting better power supply efficiency. Size can be decreased
by increasing the switching frequency at the expense of
efficiency. Cost can be minimized by using through-hole
inductors and capacitors; however these components are
physically large.
To start the design, select a switching frequency based on
Table 13. This frequency is a starting point and may be adjusted
as the design progresses.
INDUCTOR SELECTION
The output inductor selection process must include several trade-
offs. A high inductance value will result in a low ripple current
(Iopp), which will reduce output capacitance and produce a low
output ripple voltage, but may also compromise output transient
load performance. Therefore, a balance must be struck between
output ripple and optimal load transient performance. A good
starting point is to select the output inductor ripple equal to the
expected load transient step magnitude (Iostep):
TABLE 11. Switching Frequency Resistor Settings
RSYNC
(k)
fSW
(kHz)
10 200
11 222
12.1 242
13.3 267
14.7 296
16.2 320
17.8 364
19.6 400
21.5 421
23.7 471
26.1 533
28.7 571
31.6 615
34.8 727
38.3 800
46.4 889
51.1 1000
56.2 1143
68.1 1333
TABLE 12. Power Supply Requirements
Parameter Range Example Value
Input voltage (VIN)3.0V to 14.0V12V
Output voltage (VOUT) 0.6V to 5.0V 1.2V
Output current (IOUT) 0A to ~25A 20A
Output voltage ripple
(Vorip)
< 3% of VOUT 1% of VOUT
Output load step (Iostep) < Io 50% of Io
Output load step rate — 10A/µs
Output deviation due to load step — ± 50mV
Maximum PCB temp. +120°C +85°C
Desired efficiency — 85%
Other considerations Various Optimize for small
size
TABLE 13. Circuit Design Consideration
Frequency Range Efficiency Circuit Size
200kHz to 400kHz Highest Larger
400kHz to 800kHz Moderate Smaller
800kHz to 1.4MHz Lower Smallest
ostepopp II
(EQ. 4)
ZL2008
FN6859 Rev 4.00 Page 19 of 43
April 29, 2011
Now the output inductance can be calculated using Equation 5,
where VINM is the maximum input voltage:
The average inductor current is equal to the maximum output
current. The peak inductor current (ILpk) is calculated using
Equation 6 where IOUT is the maximum output current:
Select an inductor rated for the average DC current with a peak
current rating above the peak current computed above.
In overcurrent or short-circuit conditions, the inductor may have
currents greater than 2X the normal maximum rated output
current. It is desirable to use an inductor that still provides some
inductance to protect the load and the MOSFETs from damaging
currents in this situation.
Once an inductor is selected, the DCR and core losses in the
inductor are calculated. Use the DCR specified in the inductor
manufacturer’s datasheet.
ILrms is given by Equation 8:
where IOUT is the maximum output current. Next, calculate the
core loss of the selected inductor. Since this calculation is
specific to each inductor and manufacturer, refer to the chosen
inductor datasheet. Add the core loss and the ESR loss and
compare the total loss to the maximum power dissipation
recommendation in the inductor datasheet.
OUTPUT CAPACITOR SELECTION
Several trade-offs must also be considered when selecting an
output capacitor. Low ESR values are needed to have a small
output deviation during transient load steps (Vosag) and low
output voltage ripple (Vorip). However, capacitors with low ESR,
such as semi-stable (X5R and X7R) dielectric ceramic capacitors,
also have relatively low capacitance values. Many designs can
use a combination of high capacitance devices and low ESR
devices in parallel.
For high ripple currents, a low capacitance value can cause a
significant amount of output voltage ripple. Likewise, in high
transient load steps, a relatively large amount of capacitance is
needed to minimize the output voltage deviation while the
inductor current ramps up or down to the new steady state
output current value.
As a starting point, apportion one-half of the output ripple
voltage to the capacitor ESR and the other half to capacitance, as
shown in Equations 9 and 10:
Use these values to make an initial capacitor selection, using a
single capacitor or several capacitors in parallel.
After a capacitor has been selected, the resulting output voltage
ripple can be calculated using Equation 11:
Because each part of this equation was made to be less than or
equal to half of the allowed output ripple voltage, the Vorip should
be less than the desired maximum output ripple.
INPUT CAPACITOR
It is highly recommended that dedicated input capacitors be
used in any point-of-load design, even when the supply is
powered from a heavily filtered 5V or 12V “bulk” supply from an
off-line power supply. This is because of the high RMS ripple
current that is drawn by the buck converter topology. This ripple
(ICINrms) can be determined from Equation 12:
Without capacitive filtering near the power supply circuit, this
current would flow through the supply bus and return planes,
coupling noise into other system circuitry. The input capacitors
should be rated at 1.2X the ripple current calculated above to
avoid overheating of the capacitors due to the high ripple current,
which can cause premature failure. Ceramic capacitors with X7R
or X5R dielectric with low ESR and 1.1X the maximum expected
input voltage are recommended.
BOOTSTRAP CAPACITOR SELECTION
The high-side driver boost circuit utilizes an external Schottky
diode (DB) and an external bootstrap capacitor (CB) to supply
sufficient gate drive for the high-side MOSFET driver. DB should
be a 20mA, 30V Schottky diode or equivalent device and CB
should be a 1µF ceramic type rated for at least 6.3V.
QL SELECTION
The bottom MOSFET should be selected primarily based on the
device’s RDS(ON) and secondarily based on its gate charge. To
choose QL, use the following equation and allow 2% to 5% of the
output power to be dissipated in the RDS(ON) of QL (lower output
voltages and higher step-down ratios will be closer to 5%):
opp
INM
OUT
OUT
OUT Ifsw
V
V
V
L
1
(EQ. 5)
2
opp
OUTLpk
I
II
(EQ. 6)
2
LrmsLDCR IDCRP
(EQ. 7)
12
2
2opp
OUTLrms
I
II
(EQ. 8)
2
8orip
sw
opp
OUT V
f
I
C
(EQ. 9)
opp
orip
I
V
ESR
2
(EQ. 10)
OUTsw
opp
opporip Cf
I
ESRIV
8
(EQ. 11)
)1( DDII OUTCINrms
(EQ. 12)
ZL2008
FN6859 Rev 4.00 Page 20 of 43
April 29, 2011
Calculate the RMS current in QL as follows:
Calculate the desired maximum RDS(ON) as follows:
Note that the RDS(ON) given in the manufacturer’s datasheet is
measured at +25°C. The actual RDS(ON) in the end-use
application will be much higher. For example, a Vishay Si7114
MOSFET with a junction temperature of +125°C has an RDS(ON)
that is 1.4 times higher than the value at +25°C. Select a
candidate MOSFET, and calculate the required gate drive current
as follows:
Keep in mind that the total allowed gate drive current for both QH
and QL is 80mA.
MOSFETs with lower RDS(ON) tend to have higher gate charge
requirements, which increases the current and resulting power
required to turn them on and off. Since the MOSFET gate drive
circuits are integrated in the ZL2008, this power is dissipated in
the ZL2008 according to Equation 17:
QH SELECTION
In addition to the RDS(ON) loss and gate charge loss, QH also has
switching loss. The procedure to select QH is similar to the
procedure for QL. First, assign 2% to 5% of the output power to
be dissipated in the RDS(ON) of QH using the equation for QL
above. As was done with QL, calculate the RMS current as
follows:
Calculate a starting RDS(ON) as follows, in this example using 5%:
Select a MOSFET and calculate the resulting gate drive current.
Verify that the combined gate drive current from QL and QH does
not exceed 80mA.
Next, calculate the switching time using:
where Qg is the gate charge of the selected QH and Igdr is the
peak gate drive current available from the ZL2008.
Although the ZL2008 has a typical gate drive current of 3A, use
the minimum guaranteed current of 2A for a conservative
design. Using the calculated switching time, calculate the
switching power loss in QH using:
The total power dissipated by QH is given by Equation 23:
MOSFET THERMAL CHECK
Once the power dissipations for QH and QL have been calculated,
the MOSFETs junction temperature can be estimated. Using the
junction-to-case thermal resistance (Rth) given in the MOSFET
manufacturer’s datasheet and the expected maximum printed
circuit board temperature, calculate the junction temperature as
follows:
CURRENT SENSING COMPONENTS
Once the current sense method has been selected (refer to
section “Current Limit Threshold Selection” on page 21), the
components are selected as follows.
When using the inductor DCR sensing method, the user must
also select an R/C network comprised of R1 and CL (see
Figure 15).
For the voltage across CL to reflect the voltage across the DCR of
the inductor, the time constant of the inductor must match the
time constant of the RC network. That is:
For L, use the average of the nominal value and the minimum
value. Include the effects of tolerance, DC Bias and switching
frequency on the inductance when determining the minimum
value of L. Use the typical value for DCR.
The value of R1 should be as small as feasible and no greater
than 5k for best signal-to-noise ratio. The designer should
make sure the resistor package size is appropriate for the power
dissipated and include this loss in efficiency calculations. In
calculating the minimum value of R1, the average voltage across
OUTOUTQL IVP 05.0
(EQ. 13)
DII Lrmsbotrms 1
(EQ. 14)
2
)(
botrms
QL
ONDS I
P
R
(EQ. 15)
gSWg QfI
(EQ. 16)
INMgswQL VQfP
(EQ. 17)
DII Lrmstoprms
(EQ. 18)
OUTOUTQH IVP 05.0
(EQ. 19)
2
)(
toprms
QH
ONDS I
P
R
(EQ. 20)
gdr
g
SW I
Q
t
(EQ. 21)
swOUTswINMswtop fItVP
(EQ. 22)
swtopQHQHtot PPP
(EQ. 23)
thQpcbj RPTT
max
(EQ. 24)
GH
GL
ISENA
ZL
ISENB
SW R1 CL
R2
FIGURE 15. DCR Current Sensing
DCR
L
CR L
DCRLRC
1
/
(EQ. 25)
ZL2008
FN6859 Rev 4.00 Page 21 of 43
April 29, 2011
CL (which is the average IOUTDCR product) is small and can be
neglected. Therefore, the minimum value of R1 may be
approximated Equation 26:,
where PR1pkg-max is the maximum power dissipation
specification for the resistor package and P is the derating factor
for the same parameter (eg.: PR1pkg-max = 0.0625W for 0603
package, P = 50% @ 85°C). Once R1-min has been calculated,
solve for the maximum value of CL from Equation 27:
and choose the next-lowest readily available value (e.g.: For
CL-max = 1.86µF, CL = 1.5µF is a good choice). Then substitute
the chosen value into the same equation and re-calculate the
value of R1. Choose the 1% resistor standard value closest to this
re-calculated value of R1. The error due to the mismatch of the
two time constants is expressed in Equation 28:
The value of R2 should be simply five times that of R1:
For the RDS(ON) current sensing method, the external low side
MOSFET will act as the sensing element as indicated in
Figure 16.
Current Limit Threshold Selection
It is recommended that the user include a current limiting
mechanism in their design to protect the power supply from
damage and prevent excessive current from being drawn from
the input supply in the event that the output is shorted to ground
or an overload condition is imposed on the output. Current
limiting is accomplished by sensing the current through the
circuit during a portion of the duty cycle.
Output current sensing can be accomplished by measuring the
voltage across a series resistive sensing element according to
Equation 30:
Where:
ILIM is the desired maximum current that should flow in the
circuit.
RSENSE is the resistance of the sensing element.
VLIM is the voltage across the sensing element at the point the
circuit should start limiting the output current.
The ZL2008 supports “lossless” current sensing by measuring
the voltage across a resistive element that is already present in
the circuit. This eliminates additional efficiency losses incurred
by devices that must use an additional series resistance in the
circuit.
To set the current limit threshold, the user must first select a
current sensing method. The ZL2008 incorporates two methods
for current sensing, synchronous MOSFET RDS(ON) sensing and
inductor DC resistance (DCR) sensing; Figure 16 shows a
simplified schematic for each method. The current sensing
method can be selected using the CFG2 pin, as shown in
Tables 26 and 28, or via the I2C/SMBus interface. Please refer to
Application Note AN2033 for details.
In addition to selecting the current sensing method, the ZL2008
gives the power supply designer several choices for the fault
response during over or under current condition. The user can
select the number of violations allowed before declaring fault, a
blanking time and the action taken when a fault is detected.
The blanking time represents the time when no current
measurement is taken. This is to avoid taking a reading just after
a switching transition (less accurate due to potential ringing). It is
a configurable parameter.
Once the sensing method has been selected, the user must
select the voltage threshold (VLIM), the desired current limit
threshold, and the resistance of the sensing element.
The current limit threshold voltage can be selected by simply
connecting the ILIM pin as shown in Table 14. The ground-
referenced sensing method is being used in this mode. By
default, the IOUT_CAL_GAIN is set to 1m for DCR mode and
2m for RDS mode.
PpkgR
OUTOUTIN PVDVVD
R
max1
22
max
min1
1
(EQ. 26)
DCRR L
CL
min1
max
(EQ. 27)
%1001 1
avg
L
LDCRCR
(EQ. 28)
12 5RR
(EQ. 29)
SENSELIMLIM RIV
(EQ. 30)
TABLE 14. Current Limit Threshold Voltage Pin-strap Settings
ILIM Pin
RDS VLIM
(mV)
DCR VLIM
(mV)
LOW 50 25
OPEN 60 30
HIGH 70 35
V
IN
V
OUT
GH
GL
ISENA
ZL
ISENB
SW
Inductor DCR Sensing
(V
OUT
must be less than 4.0 V)
V
IN
V
OUT
GH
GL
ISENA
ZL
ISENB
SW
MOSFET R
DS(ON)
Sensing
FIGURE 16. Current Sensing Methods
ZL2008
FN6859 Rev 4.00 Page 22 of 43
April 29, 2011
The threshold voltage can also be selected in 5mV increments by
connecting a resistor, RLIM, between the ILIM pin and ground
according to Table 15. This method is preferred if the user does not
desire to use or does not have access to the I2C/SMBus interface
and the desired threshold value is contained in Table 15.
The current limit threshold can also be set to a custom value via
the I2C/SMBus interface. Please refer to Application Note
AN2033 for further details.
Loop Compensation
The ZL2008 operates as a voltage-mode synchronous buck
controller with a fixed frequency PWM scheme. Although the
ZL2008 uses a digital control loop, it operates much like a
traditional analog PWM controller. Figure 17 is a simplified block
diagram of the ZL2008 control loop, which differs from an
analog control loop only by the constants in the PWM and
compensation blocks. As in the analog controller case, the
compensation block compares the output voltage to the desired
voltage reference and compensation zeroes are added to keep
the loop stable. The resulting integrated error signal is used to
drive the PWM logic, converting the error signal to a duty cycle to
drive the external MOSFETs.
In the ZL2008, the compensation zeros and gain are set by
configuring the FC0 and FC1 pins or via the I2C/SMBus interface
once the user has calculated the required settings. This method
eliminates the inaccuracies due to the component tolerances
associated with using external resistors and capacitors required
with traditional analog controllers.
The compensation is configured using a baseline set of PID taps
which are scaled on the factors of Gain, Q and Fn as shown in
Tables 16, 17 and 18. The parameters Gain, Q and Fn are defined
in AN2035 and are parameters of the compensator (not the
power stage being compensated).
The selection of these scaling factors is based on compensation
required for additional output capacitance used in an
application.
The scaling factors are applied to the baseline set of taps to
achieve the desired compensation results. These baseline taps
correspond to zeroes of the form:
Where Gbase = 20dB
Qbase = 2
fnbase = fSW/10
Both the baseline taps and the calculated taps determined by the
FC0 and FC1 resistors can be read via the I2C/SMBus interface.
Please refer to Application Note AN2033 for further details.
TABLE 15. Current Limit Threshold Voltage Resistor Settings
RLIM
(k)
RDS VLIM
(mV)
DCR VLIM
(mV)
10 0 0
11 5 2.5
12.1 10 5
13.3 15 7.5
14.7 20 10
16.2 25 12.5
17.8 30 15
19.6 35 17.5
21.5 40 20
23.7 45 22.5
26.1 50 25
28.7 55 27.5
31.6 60 30
34.8 65 32.5
38.3 70 35
42.2 75 37.5
46.4 80 40
51.1 85 42.5
56.2 90 45
61.9 95 47.5
68.1 100 50
75 105 52.5
82.5 110 55
90.9 115 57.5
100 120 60
TABLE 16. FC0 Pin-strap Settings
FC0 Pin Gain Scale (dB) Q-new/Q-base
LOW -12
1OPEN 0
HIGH 6
TABLE 17. FC1 Pin-strap Settings
FC1 Pin Fn-new/Fn-base
LOW
1OPEN
HIGH
D
1-D
VIN
VOUT
L
C
DPWM
R
C
Compensation
R
O
FIGURE 17. Control Loop Block Diagram
2
)2*()2(
1
basebase nbasenbase
base fQ s
fQ s
G
(EQ. 31)
ZL2008
FN6859 Rev 4.00 Page 23 of 43
April 29, 2011
TABLE 18. Loop Compensation Resistor Settings
RFC0
(k)
Gain Scale
(dB) Q-new/Q-base
RFC1
(k) Fn-new/Fn-base
10
12
0.6813 10 1.0000
11 0.4642 11 0.9050
12.1 0.3162 12.1 0.8190
13.3 0.2154 13.3 0.7411
14.7 0.1468 14.7 0.6707
16.2 0.1000 16.2 0.6070
17.8
6
0.6813 17.8 0.5493
19.6 0.4642 19.6 0.4971
21.5 0.3162 21.5 0.4498
23.7 0.2154 23.7 0.4071
26.1 0.1468 26.1 0.3684
28.7 0.1000 28.7 0.3334
31.6
0
0.6813 31.6 0.3017
34.8 0.4642 34.8 0.2730
38.3 0.3162 38.3 0.2471
42.2 0.2154 42.2 0.2236
46.4 0.1468 46.4 0.2024
51.1 0.1000 51.1 0.1831
56.2
-6
1.0000 56.2 0.1657
61.9 0.6813 61.9 0.1500
68.1 0.4642 68.1 0.1357
75 0.3162 75 0.1228
82.5 0.2154 82.5 0.1112
90.9 0.1468 90.9 0.1006
100 0.1000 100 0.0910
110
-12
0.6813 110 0.0824
121 0.4642 121 0.0745
133 0.3162 133 0.0675
147 0.2154 147 0.0611
162 0.1468 162 0.0553
178 0.1000 178 0.0500
ZL2008
FN6859 Rev 4.00 Page 24 of 43
April 29, 2011
Non-linear Response (NLR) Settings
The ZL2008 incorporates a non-linear response (NLR) loop that
decreases the response time and the output voltage deviation in
the event of a sudden output load current step. The NLR loop
incorporates a secondary error signal processing path that
bypasses the primary error loop when the output begins to
transition outside of the standard regulation limits. This scheme
results in a higher equivalent loop bandwidth than what is
possible using a traditional linear loop.
When a load current step function imposed on the output causes
the output voltage to drop below the lower regulation limit, the
NLR circuitry will force a positive correction signal that will turn
on the upper MOSFET and quickly force the output to increase.
Conversely, a negative load step (i.e. removing a large load
current) will cause the NLR circuitry to force a negative correction
signal that will turn on the lower MOSFET and quickly force the
output to decrease.
NLR can be configured using resistor pin-straps as follows:
CFG0 disables NLR or enables NLR inner thresholds to 1.5%,
2% or 3% (see Table 30).
CFG1 sets NLR inner thresholds timeout and blanking to 1
and 4 or 2 and 8 (see Table 27).
Please refer to Application Note AN2032 for more details
regarding NLR settings.
Efficiency Optimized Driver Dead-time
Control
The ZL2008 utilizes a closed loop algorithm to optimize the
dead-time applied between the gate drive signals for the top and
bottom FETs. In a synchronous buck converter, the MOSFET drive
circuitry must be designed such that the top and bottom
MOSFETs are never in the conducting state at the same time.
Potentially damaging currents flow in the circuit if both top and
bottom MOSFETs are simultaneously on for periods of time
exceeding a few nanoseconds. Conversely, long periods of time in
which both MOSFETs are off reduce overall circuit efficiency by
allowing current to flow in their parasitic body diodes.
It is therefore advantageous to minimize this dead-time to
provide optimum circuit efficiency. In the first order model of a
buck converter, the duty cycle is determined by Equation 32:
However, non-idealities exist that cause the real duty cycle to
extend beyond the ideal. Dead-time is one of those non-idealities
that can be manipulated to improve efficiency. The ZL2008 has
an internal algorithm that constantly adjusts dead-time non-
overlap to minimize duty cycle, thus maximizing efficiency. This
circuit will null out dead-time differences due to component
variation, temperature, and loading effects.
This algorithm is independent of application circuit parameters
such as MOSFET type, gate driver delays, rise and fall times and
circuit layout. In addition, it does not require drive or MOSFET
voltage or current waveform measurements.
Adaptive Diode Emulation
Most power converters use synchronous rectification to optimize
efficiency over a wide range of input and output conditions.
However, at light loads the synchronous MOSFET will typically
sink current and introduce additional energy losses associated
with higher peak inductor currents, resulting in reduced
efficiency. Adaptive diode emulation mode turns off the low-side
FET gate drive at low load currents to prevent the inductor current
from going negative, reducing the energy losses and increasing
overall efficiency. Diode emulation is available to single-phase
devices only.
Note: the overall bandwidth of the device may be reduced when
in diode emulation mode. It is recommended that diode
emulation is disabled prior to applying significant load steps.
Adaptive Frequency Control
Since switching losses contribute to the efficiency of the power
converter, reducing the switching frequency will reduce the
switching losses and increase efficiency. The ZL2008 includes
Adaptive Frequency Control mode, which effectively reduces the
observed switching frequency as the load decreases.
Adaptive frequency mode is enabled by setting bit 0 of
MISC_CONFIG to 1 and is only available while the device is
operating within Adaptive Diode Emulation Mode. As the load
current is decreased, diode emulation mode decreases the GL
on-time to prevent negative inductor current from flowing. As the
load is decreased further, the GH pulse width will begin to
decrease while maintaining the programmed frequency, fPROG
(set by the FREQ_SWITCH command).
Once the GH pulse width (D) reaches 50% of the nominal duty
cycle, DNOM (determined by Vin and Vout), the switching
frequency will start to decrease according to Equation 33:
If
then,
IN
OUT
V
V
D
(EQ. 32)
Switching
Frequency
Duty Cycle
f
MIN
f
PROG
f
SW
(D)
D
D
NOM
2
0
FIGURE 18. Adaptive Frequency
2
NOMD
MIN
NOM
MINSW fD
Dff
)(2
(EQ. 33)
ZL2008
FN6859 Rev 4.00 Page 25 of 43
April 29, 2011
Otherwise fSW(D) = fPROG
This is illustrated in Figure 18. Due to quantizing effects inside
the IC, the ZL2008 will decrease its frequency in steps between
fSW and fMIN. The quantity and magnitude of the steps will
depend on the difference between fSW and fMIN as well as the
frequency range.
Adaptive frequency mode is not available for current sharing
groups when using an external clock, or if the device is outputting
a clock signal on its SYNC pin.
Power Management Functional
Description
Input Undervoltage Lockout
The input undervoltage lockout (UVLO) prevents the ZL2008 from
operating when the input falls below a preset threshold,
indicating the input supply is out of its specified range. The UVLO
threshold (VUVLO) can be set between 2.85V and 16V using the
UVLO pin. The simplest implementation is to connect the UVLO
pin as shown in Table 19. If the UVLO pin is left unconnected, the
UVLO threshold will default to 4.5V.
If the desired UVLO threshold is not one of the listed choices, the
user can configure a threshold between 2.85V and 16V by
connecting a resistor between the UVLO pin and SGND by
selecting the appropriate resistor from Table 20.
The UVLO voltage can also be set to any value between 2.85V
and 16V via the I2C/SMBus interface.
Once an input undervoltage fault condition occurs, the device
can respond in a number of ways as follows:
1. Continue operating without interruption.
2. Continue operating for a given delay period, followed by
shutdown if the fault still exists. The device will remain in
shutdown until instructed to restart.
3. Initiate an immediate shutdown until the fault has been
cleared. The user can select a specific number of retry
attempts.
The default response from a UVLO fault is an immediate
shutdown of the device. The device will continuously check for
the presence of the fault condition. If the fault condition is no
longer present, the ZL2008 will be re-enabled.
TABLE 19. UVLO Threshold Pin-strap Settings
UVLO Pin
UVLO Threshold
(V)
LOW 3
OPEN 4.5
HIGH 10.8
TABLE 20. UVLO Threshold Resistor Settings
RUVLO
(k)
UVLO
(V)
17.8 2.85
19.6 3.14
21.5 3.44
23.7 3.79
26.1 4.18
28.7 4.59
31.6 5.06
34.8 5.57
38.3 6.13
42.2 6.75
46.4 7.42
51.1 8.18
56.2 8.99
61.9 9.9
68.1 10.9
75 12
82.5 13.2
90.9 14.54
100 16
ZL2008
FN6859 Rev 4.00 Page 26 of 43
April 29, 2011
Please refer to Application Note AN2033 for details on how to
configure the UVLO threshold or to select specific UVLO fault
response options via the I2C/SMBus interface.
Output Overvoltage Protection
The ZL2008 offers an internal output overvoltage protection
circuit that can be used to protect sensitive load circuitry from
being subjected to a voltage higher than its prescribed limits. A
hardware comparator is used to compare the actual output
voltage (seen at the VSEN pin) to a threshold set to 15% higher
than the target output voltage (the default setting). If the VSEN
voltage exceeds this threshold, the PG pin will de-assert and the
device can then respond in a number of ways as follows:
1. Initiate an immediate shutdown until the fault has been
cleared. The user can select a specific number of retry
attempts.
2. Turn off the high-side MOSFET and turn on the low-side
MOSFET. The low-side MOSFET remains ON until the device
attempts a restart.
The default response from an overvoltage fault is to immediately
shut down. The device will continuously check for the presence of
the fault condition, and when the fault condition no longer exists
the device will be re-enabled.
For continuous overvoltage protection when operating from an
external clock, the only allowed response is an immediate
shutdown.
Please refer to Application Note AN2033 for details on how to
select specific overvoltage fault response options via I2C/SMBus.
Output Pre-Bias Protection
An output pre-bias condition exists when an externally applied
voltage is present on a power supply’s output before the power
supply’s control IC is enabled. Certain applications require that
the converter not be allowed to sink current during start up if a
pre-bias condition exists at the output. The ZL2008 provides
pre-bias protection by sampling the output voltage prior to
initiating an output ramp.
If a pre-bias voltage lower than the target voltage exists after the
pre-configured delay period has expired, the target voltage is set
to match the existing pre-bias voltage and both drivers are
enabled. The output voltage is then ramped to the final
regulation value at the ramp rate set by the SS pin.
The actual time the output will take to ramp from the pre-bias
voltage to the target voltage will vary depending on the pre-bias
voltage but the total time elapsed from when the delay period
expires and when the output reaches its target value will match
the pre-configured ramp time. See Figure 19.
If a pre-bias voltage higher than the target voltage exists after the
pre-configured delay period has expired, the target voltage is set
to match the existing pre-bias voltage and both drivers are
enabled with a PWM duty cycle that would ideally create the
pre-bias voltage.
Once the pre-configured soft-start ramp period has expired, the
PG pin will be asserted (assuming the pre-bias voltage is not
higher than the overvoltage limit). The PWM will then adjust its
duty cycle to match the original target voltage and the output will
ramp down to the pre-configured output voltage.
If a pre-bias voltage higher than the overvoltage limit exists, the
device will not initiate a turn-on sequence and will declare an
overvoltage fault condition to exist. In this case, the device will
respond based on the output overvoltage fault response method
that has been selected. See “Output Overvoltage Protection” on
page 26 for response options due to an overvoltage condition.
Pre-bias protection is not offered for current sharing groups that
also have tracking enabled.
Output Overcurrent Protection
The ZL2008 can protect the power supply from damage if the
output is shorted to ground or if an overload condition is imposed
on the output. Once the current limit threshold has been selected
(see “Current Limit Threshold Selection” on page 21), the user
may determine the desired course of action in response to the
fault condition. The following overcurrent protection response
options are available:
1. Initiate a shutdown and attempt to restart an infinite number
of times with a preset delay period between attempts.
2. Initiate a shutdown and attempt to restart a preset number of
times with a preset delay period between attempts.
3. Continue operating for a given delay period, followed by
shutdown if the fault still exists.
FIGURE 19. Output Responses to Pre-bias Voltages
ZL2008
FN6859 Rev 4.00 Page 27 of 43
April 29, 2011
4. Continue operating through the fault (this could result in
permanent damage to the power supply).
5. Initiate an immediate shutdown.
The default response from an overcurrent fault is an immediate
shutdown of the device. The device will continuously check for
the presence of the fault condition, and if the fault condition no
longer exists the device will be re-enabled.
Please refer to Application Note AN2033 for details on how to
select specific overcurrent fault response options via I2C/SMBus.
Thermal Overload Protection
The ZL2008 includes an on-chip thermal sensor that
continuously measures the internal temperature of the die and
shuts down the device when the temperature exceeds the preset
limit. The default temperature limit is set to +125°C in the
factory, but the user may set the limit to a different value if
desired. See Application Note AN2033 for details. Note that
setting a higher thermal limit via the I2C/SMBus interface may
result in permanent damage to the device. Once the device has
been disabled due to an internal temperature fault, the user may
select one of several fault response options as follows:
1. Initiate a shutdown and attempt to restart an infinite number
of times with a preset delay period between attempts.
2. Initiate a shutdown and attempt to restart a preset number of
times with a preset delay period between attempts.
3. Continue operating for a given delay period, followed by
shutdown if the fault still exists.
4. Continue operating through the fault (this could result in
permanent damage to the power supply).
5. Initiate an immediate shutdown.
If the user has configured the device to restart, the device will
wait the preset delay period (if configured to do so) and will then
check the device temperature. If the temperature has dropped
below a threshold that is approx +15°C lower than the selected
temperature fault limit, the device will attempt to re-start. If the
temperature still exceeds the fault limit the device will wait the
preset delay period and retry again.
The default response from a temperature fault is an immediate
shutdown of the device. The device will continuously check for
the fault condition, and once the fault has cleared the ZL2008
will be re-enabled.
Please refer to Application Note AN2033 for details on how to
select specific temperature fault response options via
I2C/SMBus.
Voltage Tracking
Numerous high performance systems place stringent demands
on the order in which the power supply voltages are turned on.
This is particularly true when powering FPGAs, ASICs, and other
advanced processor devices that require multiple supply voltages
to power a single die. In most cases, the I/O interface operates at
a higher voltage than the core and therefore the core supply
voltage must not exceed the I/O supply voltage according to the
manufacturers' specifications.
Voltage tracking protects these sensitive ICs by limiting the
differential voltage between multiple power supplies during the
power-up and power down sequence. The ZL2008 integrates a
lossless tracking scheme that allows its output to track a voltage
that is applied to the VTRK pin with no external components
required. The VTRK pin is an analog input that, when tracking
mode is enabled, configures the voltage applied to the VTRK pin
to act as a reference for the device’s output regulation.
The ZL2008 offers two mode of tracking as follows:
1. Coincident. This mode configures the ZL2008 to ramp its
output voltage at the same rate as the voltage applied to the
VTRK pin.
2. Ratiometric. This mode configures the ZL2008 to ramp its
output voltage at a rate that is a percentage of the voltage
applied to the VTRK pin. The default setting is 50%, but an
external resistor string may be used to configure a different
tracking ratio.
Figure 20 illustrates the typical connection and the two tracking
modes.
The master ZL2008 device in a tracking group is defined as the
device that has the highest target output voltage within the group.
This master device will control the ramp rate of all tracking devices
and is not configured for tracking mode. A delay of at least 10ms
must be configured into the master device using the SS pin, and the
user may also configure a specific ramp rate using the SS pin. Any
device that is configured for tracking mode will ignore its soft-start
delay and ramp time settings (SS pin) and its output will take on the
turn-on/turn-off characteristics of the reference voltage present at
the VTRK pin. All of the ENABLE pins in the tracking group must be
connected together and driven by a single logic source. Tracking is
configured via the I2C/SMBus interface by using the TRACK_CONFIG
PMBus command. Please refer to Application Note AN2033 for
more information on configuring tracking mode using PMBus.
ZL2008
FN6859 Rev 4.00 Page 28 of 43
April 29, 2011
It should be noted that current sharing groups that are also
configured to track another voltage do not offer pre-bias
protection; a minimum load should therefore be enforced to
avoid the output voltage from being held up by an outside force.
Additionally, a device set up for tracking must have both
Alternate Ramp Control and Precise Ramp-Up Delay disabled.
Voltage Margining
The ZL2008 offers a simple means to vary its output higher or
lower than its nominal voltage setting in order to determine
whether the load device is capable of operating over its specified
supply voltage range. The MGN command is set by driving the
MGN pin or through the I2C/SMBus interface. The MGN pin is a
tri-level input that is continuously monitored and can be driven
directly by a processor I/O pin or other logic-level output.
The ZL2008’s output will be forced higher than its nominal set
point when the MGN command is set HIGH, and the output will
be forced lower than its nominal set point when the MGN
command is set LOW. Default margin limits of VNOM ±5% are
pre-loaded in the factory, but the margin limits can be modified
through the I2C/SMBus interface to as high as VNOM + 10% or as
low as 0V, where VNOM is the nominal output voltage set point
determined by the V0 and V1 pins. A safety feature prevents the
user from configuring the output voltage to exceed VNOM + 10%
under any conditions.
The margin limits and the MGN command can both be set
individually through the I2C/SMBus interface. Additionally, the
transition rate between the nominal output voltage and either
margin limit can be configured through the I2C interface. Please
refer to Application Note AN2033 for detailed instructions on
modifying the margining configurations.
I2C/SMBus Communications
The ZL2008 provides an I2C/SMBus digital interface that
enables the user to configure all aspects of the device operation
as well as monitor the input and output parameters. The ZL2008
can be used with any standard 2-wire I2C host device. In addition,
the device is compatible with SMBus version 2.0 and includes an
SALRT line to help mitigate bandwidth limitations related to
continuous fault monitoring. Pull-up resistors are required on the
I2C/SMBus as specified in the SMBus 2.0 specification. The
ZL2008 accepts most standard PMBus commands. When
controlling the device with PMBus commands, it is
recommended that the enable pin is tied to SGND.
TABLE 21. Tracking Resistor Settings
RSS
(k)
Track Ratio
(%) Upper Track Limit Ramp-up/down Behavior
90.9
100
Limited by target
Output does not decrease before PG
100 Output always follows VTRK
110
Limited by VTRK
Output does not decrease before PG
121 Output always follows VTRK
133
50
Limited by target
Output does not decrease before PG
147 Output always follows VTRK
162
Limited by VTRK
Output does not decrease before PG
178 Output always follows VTRK
VOUT
V
OUT
Time
Coincident
Ratiometric
VTRK
V
IN
V
OUT
Q1
Q2
L1
C1
GH
GL
SW
ZL
VTRK
V
TRK
VOUT
V
OUT
Time
VTRK
FIGURE 20. Tracking Modes
ZL2008
FN6859 Rev 4.00 Page 29 of 43
April 29, 2011
I2C/SMBus Device Address Selection
When communicating with multiple SMBus devices using the
I2C/SMBus interface, each device must have its own unique
address so the host can distinguish between the devices. The
device address can be set according to the pin-strap options
listed in Table 22. Address values are right-justified.
If additional device addresses are required, a resistor can be
connected to the SA0 pin according to Table 23 to provide up to
25 unique device addresses. In this case, the SA1 pin should be
tied to SGND.
If more than 25 unique device addresses are required or if other
SMBus address values are desired, both the SA0 and SA1 pins
can be configured with a resistor to SGND according to
Equation 34 and Table 24.
Using this method, the user can theoretically configure up to 625
unique SMBus addresses, however the SMBus is inherently
limited to 128 devices so attempting to configure an address
higher than 128 (0x80) will cause the device address to repeat
(i.e., attempting to configure a device address of 129 (0x81)
would result in a device address of 1). Therefore, the user should
use index values 0-4 on the SA1 pin and the full range of index
values on the SA0 pin, which will provide 125 device address
combinations.
Note that the SMBus address 0x4B is reserved for device test and
cannot be used in the system.
TABLE 22. SMBus Address Pin-strap Selection
SA0
LOW OPEN HIGH
SA1
LOW 0x20 0x21 0x22
OPEN 0x23 0x24 0x25
HIGH 0x26 0x27 Reserved
TABLE 23. SMBus Address Resistor Selection
RSA0
(k)
SMBus
Address
10 0x00
11 0x01
12.1 0x02
13.3 0x03
14.7 0x04
16.2 0x05
17.8 0x06
19.6 0x07
21.5 0x08
23.7 0x09
26.1 0x0A
28.7 0x0B
31.6 0x0C
34.8 0x0D
38.3 0x0E
42.2 0x0F
46.4 0x10
51.1 0x11
56.2 0x12
61.9 0x13
68.1 0x14
75 0x15
82.5 0x16
90.9 0x17
100 0x18
TABLE 24. SMBus Address Index Values
RSA
(k) SA0 or SA1 Index
10 0
11 1
12.1 2
13.3 3
14.7 4
16.2 5
17.8 6
19.6 7
21.5 8
23.7 9
26.1 10
28.7 11
31.6 12
34.8 13
38.3 14
42.2 15
46.4 16
51.1 17
56.2 18
61.9 19
68.1 20
75 21
82.5 22
90.9 23
100 24
(EQ. 34)
SMBus address = 25 x (SA1 index) + (SA0 index) (in decimal)
ZL2008
FN6859 Rev 4.00 Page 30 of 43
April 29, 2011
Digital-DC Bus
The Digital-DC Communications (DDC) bus is used to
communicate between Zilker Labs Digital-DC devices. This
dedicated bus provides the communication channel between
devices for features such as sequencing, fault spreading, and
current sharing. The DDC pin on all Digital-DC devices in an
application should be connected together. A pull-up resistor is
required on the DDC bus in order to guarantee the rise time as
follows:
where RPU is the DDC bus pull-up resistance and CLOAD is the bus
loading. The pull-up resistor may be tied to VR or to an external
3.3V or 5V supply as long as this voltage is present prior to or
during device power-up. As rules of thumb, each device
connected to the DDC bus presents approx 10pF of capacitive
loading, and each inch of FR4 PCB trace introduces approx 2pF.
The ideal design will use a central pull-up resistor that is well-
matched to the total load capacitance. In power module
applications, the user should consider whether to place the pull-
up resistor on the module or on the PCB of the end application.
The minimum pull-up resistance should be limited to a value that
enables any device to assert the bus to a voltage that will ensure
a logic 0 (typically 0.8V at the device monitoring point) given the
pull-up voltage (5V if tied to VR) and the pull-down current
capability of the ZL2008 (nominally 4mA).
Phase Spreading
When multiple point of load converters share a common DC
input supply, it is desirable to adjust the clock phase offset of
each device such that not all devices start to switch
simultaneously. Setting each converter to start its switching cycle
at a different point in time can dramatically reduce input
capacitance requirements and efficiency losses. Since the peak
current drawn from the input supply is effectively spread out over
a period of time, the peak current drawn at any given moment is
reduced and the power losses proportional to the IRMS2 are
reduced dramatically.
In order to enable phase spreading, all converters must be
synchronized to the same switching clock. The CFG1 pin is used
to set the configuration of the SYNC pin for each device as
described in section “Switching Frequency and PLL” on page 17 .
The phase offset of each single-phase device may be set to any
value between 0° and 337.5° in 22.5° increments using the
CFG2 pin as shown in Tables 25 and 26.
The phase offset of (multi-phase) current sharing devices is
automatically set to a value between 0° and 337.5° in 22.5°
increments as described in “Active Current Sharing” on page 31.
The phase offset of each device may also be set to any value
between 0° and 360° in 22.5° increments via the I2C/SMBus
interface. Refer to Application Note AN2033 for further details.
TABLE 25. Phase Offset Pin-strap Settings
RCFG2
Phase Offset
(°) Current Sense
LOW 90
DCROPEN 0
HIGH 180
(EQ. 35)
Rise time = R
PU
* C
LOAD
1µs
TABLE 26. Phase Offset Resistor Settings
RCFG2
(k)
Phase Offset
(°)
Current
Sense
10 22.5
DCR
11 45
12.1 67.5
13.3 90
14.7 112.5
16.2 135
17.8 157.5
19.6 180
21.5 202.5
23.7 225
26.1 247.5
28.7 270
31.6 292.5
34.8 315
38.3 337.5
42.2 22.5
RDS
46.4 45
51.1 67.5
56.2 90
61.9 112.5
68.1 135
75 157.5
82.5 180
90.9 202.5
100 225
110 247.5
121 270
133 292.5
147 315
162 337.5
ZL2008
FN6859 Rev 4.00 Page 31 of 43
April 29, 2011
Output Sequencing
A group of Digital-DC devices may be configured to power up in a
predetermined sequence. This feature is especially useful when
powering advanced processors, FPGAs, and ASICs that require
one supply to reach its operating voltage prior to another supply
reaching its operating voltage in order to avoid latch-up from
occurring. Multi-device sequencing can be achieved by
configuring each device through the I2C/SMBus interface or by
using Zilker Labs patented autonomous sequencing mode.
Autonomous sequencing mode configures sequencing by using
events transmitted between devices over the DDC bus. This mode
is not available on current sharing rails.
The sequencing order is determined using each device’s SMBus
address. Using autonomous sequencing mode (configured using
the CFG1 pin), the devices must be assigned sequential SMBus
addresses with no missing addresses in the chain. This mode will
also constrain each device to have a phase offset according to its
SMBus address as described “Phase Spreading” on page 30.
The sequencing group will turn on in order starting with the
device with the lowest SMBus address and will continue through
to turn on each device in the address chain until all devices
connected have been turned on. When turning off, the device
with the highest SMBus address will turn off first followed in
reverse order by the other devices in the group.
Sequencing is configured by connecting a resistor from the CFG1
pin to ground as described in Table 27. The CFG1 pin is also used
to set the configuration of the SYNC pin as well as to determine
the sequencing method and order. Please refer to “Switching
Frequency and PLL” on page 17 for more details on the operating
parameters of the SYNC pin.
Multiple device sequencing may also be achieved by issuing
PMBus commands to assign the preceding device in the
sequencing chain as well as the device that will follow in the
sequencing chain. This method places fewer restrictions on
SMBus address (no need of sequential address) and also allows
the user to assign any phase offset to any device irrespective of
its SMBus device address.
The Enable pins of all devices in a sequencing group must be tied
together and driven high to initiate a sequenced turn-on of the
group. Enable must be driven low to initiate a sequenced turnoff
of the group.
Refer to Application Note AN2033 for details on sequencing via
the I2C/SMBus interface.
Fault Spreading
Digital DC devices can be configured to broadcast a fault event
over the DDC bus to the other devices in the group. When a non-
destructive fault occurs and the device is configured to shut down
on a fault, the device will shut down and broadcast the fault
event over the DDC bus. The other devices on the DDC bus will
shut down together or in sequencing order, if configured to do so,
and will attempt to re-start in their prescribed order if configured
to do so.
Temperature Monitoring Using the XTEMP Pin
The ZL2008 supports measurement of an external device
temperature using either a thermal diode integrated in a
processor, FPGA or ASIC, or using a discrete diode-connected
2N3904 NPN transistor. Figure 21 illustrates the typical
connections required.
Active Current Sharing
Paralleling multiple ZL2008 devices can be used to increase the
output current capability of a single power rail. By connecting the
DDC pins of each device together and configuring the devices as
a current sharing rail, the units will share the current equally
within a few percent.
Figure 22 illustrates a typical connection for three devices.
The ZL2008 uses a low-bandwidth, first-order digital current
sharing technique to balance the unequal device output loading
by aligning the load lines of member devices to a reference
device.
Droop resistance is used to add artificial resistance in the output
voltage path to control the slope of the load line curve,
calibrating out the physical parasitic mismatches due to power
train components and PCB layout.
ZL
SGND
XTEMP
Discrete NPN
2N3904
ZL
SGND
XTEMP
Embedded Thermal Diode
µP
FPGA
DSP
ASIC
100 pF
100 pF
FIGURE 21. External Temperature Monitoring
ZL2008
FN6859 Rev 4.00 Page 32 of 43
April 29, 2011
TABLE 27. Sequencing Pin-strap and Resistor Settings
RCFG1 SYNC Pin Config Sequencing Configuration
NLR Timeout and
Blanking
LOW Input
Sequencing is disabled. 1 and 4OPEN Auto detect
HIGH Output
10kInput
Sequencing is disabled.
1 and 4
11kAuto detect
12.1kOutput
14.7kInput
The ZL2008 is configured as the first device in a nested sequencing group. Turn on
order is based on the device SMBus address.
16.2kAuto detect
17.8kOutput
21.5kInput
The ZL2008 is configured as a last device in a nested sequencing group. Turn on order
is based on the device SMBus address.
23.7kAuto detect
26.1kOutput
31.6kInput
The ZL2008 is configured as the middle device in a nested sequencing group. Turn on
order is based on the device SMBus address.
34.8kAuto detect
38.3kOutput
46.4kInput
Sequencing is disabled.
2 and 8
51.1kAuto detect
56.2kOutput
68.1kInput
The ZL2008 is configured as the first device in a nested sequencing group. Turn on
order is based on the device SMBus address.
75kAuto detect
82.5kOutput
100kInput
The ZL2008 is configured as a last device in a nested sequencing group. Turn on order
is based on the device SMBus address.
110kAuto detect
121kOutput
147kInput
The ZL2008 is configured as the middle device in a nested sequencing group. Turn on
order is based on the device SMBus address.
162kAuto detect
178kOutput
ZL2008
FN6859 Rev 4.00 Page 33 of 43
April 29, 2011
Upon system start-up, the device with the lowest member
position as selected in ISHARE_CONFIG is defined as the
reference device. The remaining devices are members. The
reference device broadcasts its current over the DDC bus. The
members use the reference current information to trim their
voltages (VMEMBER) to balance the current loading of each device
in the system.
Figure 23 shows that, for load lines with identical slopes, the
member voltage is increased towards the reference voltage
which closes the gap between the inductor currents.
The relation between reference and member current and voltage
is given by Equation 36:
where R is the value of the droop resistance.
The ISHARE_CONFIG command is used to configure the device
for active current sharing. The default setting is a stand-alone
non-current sharing device. A current sharing rail can be part of a
system sequencing group.
For fault configuration, the current share rail is configured in a
quasi-redundant mode. In this mode, when a member device
fails, the remaining members will continue to operate and
attempt to maintain regulation. Of the remaining devices, the
device with the lowest member position will become the
reference. If fault spreading is enabled, the current share rail
failure is not broadcast until the entire current share rail fails.
Up to eight (8) devices can be configured in a given current
sharing rail.
ZL
V
OUT
ZL
ZL
V
IN
C
OUT
C
IN
C
OUT
C
IN
C
OUT
C
IN
DDC
DDC
DDC
3.3V - 5V
FIGURE 22. Current Sharing Group
-R
-R
V
REFERENCE
V
MEMBER
I
MEMBER
I
REFERENCE
I
OUT
V
OUT
FIGURE 23. Active Current Sharing
MEMBERREFERENCEOUTMEMBER IIRVV
(EQ. 36)
TABLE 28. Current Share Position Settings
RCFG2
(k) Current Share Position Current Sense
10 0
DCR
11 1
12.1 2
13.3 3
14.7 4
16.2 5
17.8 6
19.6 7
42.2 0
RDS
46.4 1
51.1 2
56.2 3
61.9 4
68.1 5
75 6
82.5 7
TABLE 29. Current Share Pin-strap Settings
CFG0 Pin NLR
Current Share # of
Members Current Sharing
LOW 1.5%
0 Disabled
OPEN Disabled
HIGH 2%
ZL2008
FN6859 Rev 4.00 Page 34 of 43
April 29, 2011
The phase offset of a current sharing group is automatically set
to a value between 0° and 337.5° in 22.5° increments as
follows:
The phase of the individual members in a group are spread
evenly from the phase offset of the group.
Please refer to Application Note AN2034 for additional details on
current sharing.
Phase Adding/Dropping
The ZL2008 allows multiple power converters to be connected in
parallel to supply higher load currents than can be addressed
using a single-phase design. In doing so, the power converter is
optimized at a load current range that requires all phases to be
operational. During periods of light loading, it may be beneficial
to disable one or more phases in order to eliminate the current
drain and switching losses associated with those phases,
resulting in higher efficiency.
The ZL2008 offers the ability to add and drop phases using a the
phase enable pin or a PMBus command in response to an
observed load current change. All phases in a current share rail
are considered active prior to the current sharing rail ramp to
power-good.
Phases can be dropped after power-good is reached. The phase
enable pin can be used to drop and add phases:
• Set PH_EN = 0 to drop a phase
• Set PH_EN = 1 to add a phase
The time to detect a change of state of the phase enable pin is
between 0ms and 3ms (max).
Any member of the current sharing rail can be dropped. If the
reference device is dropped, the remaining active device with the
lowest member position will become the new reference.
Additionally, any change to the number of members of a current
sharing rail will precipitate autonomous phase distribution within
the rail where all active phases realign their phase position
based on their order within the number of active members.
If the members of a current sharing rail are forced to shut down
due to an observed fault, all members of the rail will attempt to
re-start simultaneously after the fault has cleared.
For single phase operation, that is, not current sharing, the
PH_EN pin is ignored and can be left open.
TABLE 30. Current Share Resistor Settings
RCFG0
(k)NLR
Current Share # of
Members Current Sharing
10
Disabled
2
Enabled
11 3
12.1 4
13.3 5
14.7 6
16.2 7
17.8 8
19.6
3%
0 Disabled
21.5 2
Enabled
23.7 3
26.1 4
28.7 5
31.6 6
34.8 7
38.3 8
42.2
2%
0 Disabled
46.4 2
Enabled
51.1 3
56.2 4
61.9 5
68.1 6
75 7
82.5 8
90.9
1.5%
0 Disabled
100 2
Enabled
110 3
121 4
133 5
147 6
162 7
178 8
(EQ. 37)
Phase Offset = (SMBus Address[4:0] – Current Share
Position) * 22.5°
ZL2008
FN6859 Rev 4.00 Page 35 of 43
April 29, 2011
Monitoring via I2C/SMBus
A system controller can monitor a wide variety of different
ZL2008 system parameters through the I2C/SMBus interface.
The device can monitor for fault conditions by monitoring the
SALRT pin, which will be pulled low when any number of
pre-configured fault conditions occur.
The device can also be monitored continuously for any number of
power conversion parameters including but not limited to the
following:
• Input voltage/Output voltage
• Output current
• Internal and external temperature
•Switching frequency
• Duty cycle
The PMBus Host should respond to SALRT as follows:
1. ZL device pulls SALRT Low
2. PMBus Host detects that SALRT is now low, performs
transmission with Alert Response Address to find which ZL
device is pulling SALRT low.
3. PMBus Host talks to the ZL device that has pulled SALRT low.
The actions that the host performs are up to the System
Designer.
If multiple devices are faulting, SALRT will still be low after doing
the above steps and will require transmission with the Alert
Response Address repeatedly until all faults are cleared.
Please refer to Application Note AN2033 for details on how to
monitor specific parameters via the I2C/SMBus interface.
Snapshot Parameter Capture
The ZL2008 offers a special feature that enables the user to
capture parametric data during normal operation or following a
fault. The Snapshot functionality is enabled by setting bit 1 of
MISC_CONFIG to 1.
See AN2033 for details on using the Snapshot in addition to the
parameters supported. The Snapshot feature enables the user to
read status and parameters via a block read transfer through the
SMBus. This can be done during normal operation, although it
should be noted that reading the 22 bytes will occupy the SMBus
for some time.
The SNAPSHOT_CONTROL command enables the user to store
the snapshot parameters to Flash memory in response to a
pending fault as well as to read the stored data from Flash
memory after a fault has occurred. Table 31 describes the usage
of this command. Automatic writes to Flash memory following a
fault are triggered when any fault threshold level is exceeded,
provided that the specific fault’s response is to shut down
(writing to Flash memory is not allowed if the device is configured
to re-try following the specific fault condition). It should also be
noted that the device’s VDD voltage must be maintained during
the time when the device is writing the data to Flash memory; a
process that requires between 700µs to 1400µs depending on
whether the data is set up for a block write. Undesirable results
may be observed if the device’s VDD supply drops below 3.0V
during this process.
In the event that the device experiences a fault and power is lost,
the user can extract the last SNAPSHOT parameters stored
during the fault by writing a 1 to SNAPSHOT_CONTROL (transfers
data from Flash memory to RAM) and then issuing a SNAPSHOT
command (reads data from RAM via SMBus).
Non-Volatile Memory and Device Security
Features
The ZL2008 has internal non-volatile memory where user
configurations are stored. Integrated security measures ensure
that the user can only restore the device to a level that has been
made available to them. Refer to “Start-up Procedure” on
page 15 for details on how the device loads stored values from
internal memory during start-up.
During the initialization process, the ZL2008 checks for stored
values contained in its internal non-volatile memory. The ZL2008
offers two internal memory storage units that are accessible by
the user as follows:
1. Default Store: A power supply module manufacturer may
want to protect the module from damage by preventing the
user from being able to modify certain values that are related
to the physical construction of the module. In this case, the
module manufacturer would use the Default Store and would
allow the user to restore the device to its default setting but
would restrict the user from restoring the device to the factory
settings.
2. User Store: The manufacturer of a piece of equipment may
want to provide the ability to modify certain power supply
settings while still protecting the equipment from modifying
values that can lead to a system level fault. The equipment
manufacturer would use the User Store to achieve this goal.
Please refer to Application Note AN2033 for details on how to set
specific security measures via the I2C/SMBus interface.
Pin-strap Current Sharing
Configuration
A 3-phase current sharing group example is shown in Figure 24.
Each ZL2008 device in the group is connected to the same DDC
bus and SMBus. Also, the enable pins are connected together to
allow all devices in the current sharing group to enable
simultaneously.
The device with the lowest position number becomes the
reference device. The reference device provides the load current
information to each member device. If the reference device is
TABLE 31. SNAPSHOT_CONTROL Command
Data Value Description
1 Copies current SNAPSHOT values from Flash memory to
RAM for immediate access using SNAPSHOT command.
2 Writes current SNAPSHOT values to Flash memory. Only
available when device is disabled.
ZL2008
FN6859 Rev 4.00 Page 36 of 43
April 29, 2011
dropped or faults then the device with the next lowest position
number will become the new reference device.
SMBus Address (SA0, SA1 Pins)
Assign sequential SMBus addresses to each device in the current
sharing group. If other non-current sharing devices are connected
to the same SMBus then assign addresses to these devices that
are before or after the current sharing group.
Current Share Pin-Straps (CFG0, CFG2 Pins)
Resistor pin-strap the CFG0 pin to set the following parameters:
a. Current Share # of Members – Number of devices or phases
in a current sharing group (2 minimum and 8 maximum).
b. Current Share Control – Current sharing is automatically
enabled when the number of members is 2 (and disabled
when members is = 0).
Resistor pin-strap the CFG2 pin to set the current share position:
c. Current Share Position – Sequential numbering from 0 to 7
(max) of N number of members starting with the reference
device in position 0 and ending with the last member device
in position N-1.
For the 3-phase group the parameters for each device are shown
in Table 32.
SYNC Clock (CFG1 Pin)
Typically the reference device sources the SYNC clock. However,
any device internal or external to the current sharing group can
source the SYNC clock. If the reference device is sourcing the
SYNC clock, then resistor pin-strap the CFG1 pin to configure the
SYNC pin as an output. Otherwise configure the reference
device’s SYNC pin as an input. For member devices, resistor
pin-strap the CFG1 pin to configure the SYNC pin as an input.
Soft-start (SS Pin)
Current sharing groups require proper synchronization prior to
ramp events. Resistor pin-strap the SS pin to set the following
parameters:
a. Delay Time – The reference device’s soft-start delay time
must be at least 10ms greater than any member device to
ramp up/down current sharing. The reference device requires
this additional time to coordinate a synchronization signal to
all member devices.
b. Ramp Time – A minimum soft-start ramp time of 5ms is
required for both reference and member devices to ramp
up/down current sharing.
Phase Enable (PH_EN Pin)
Phase enable is used to dynamically add or drop a current
sharing phase during operation. Set the PH_EN pin high to
enable a phase and low to disable a phase (open is an invalid
state). The PH_EN pin replaces the PHASE_CONTROL command.
For proper operation, the pin must be externally driven high or
low without switching glitches. Also, ensure phase enable is high
for the reference and member devices of a current sharing group
prior to ramp-up.
MFR_CONFIG Command
Application specific values are set by the MFR_CONFIG
command. The following parameters must be set to properly
configure current sharing.
a. Current Sense Blanking Delay (bits 15:11) – The current
sense delay parameter controls the blanking time when no
current measurement is taken. This allows the filtering of
noise from the current measurement circuit when the FETs
are switching. The actual value selected depends on fSW,
sensing method and ring-out duration. The same delay is
used for both reference and member devices.
b. Current Sense Control (bits 5:4) – Three modes of current
sensing are available depending on duty cycle and switching
frequency as listed in Table 33 (also refer to “Current Limit
Threshold Selection” on page 21). The same sensing is used
for both reference and member devices.
TABLE 32. Current Share Parameters
Device SMBus Address # of Members Position Control
Reference 0x20 3 0 Enabled
Member_1 0x21 3 1 Enabled
Member_2 0x22 3 2 Enabled
Rail_1
Rail DDC ID = 5
DEV_2
0x21
Rout Cout
SCL
DDC
PH_3
PH_2
PH_1
3.3V VCC
DEV_3
0x22
SYNC_Out
VCC
VCC
SDA
MEM_1
POS_2
REF.
POS_1
MEM_2
POS_3
DEV_1
0x20
SYNC_In
SYNC
SYNC_In
POS_0
POS_1
POS_2
Rail_1
Rail DDC ID = 5
DEV_2
0x21
Rout Cout
SCL
DDC
PH_3
PH_2
PH_1
3.3V VCC
DEV_3
0x22
SYNC_Out
VCC
VCC
SDA
MEM_1
POS_2
REF.
POS_1
MEM_2
POS_3
DEV_1
0x20
SYNC_In
SYNC
SYNC_In
POS_0
POS_1
POS_2
FIGURE 24. 3-phase Current Sharing Group
ZL2008
FN6859 Rev 4.00 Page 37 of 43
April 29, 2011
Note, the following parameters are automatically set when
current sharing is enabled.
Alternate Ramp Control (bit 2) – Automatically set to “1”
(enabled) for both reference and member devices when current
sharing is enabled.
SYNC Pin Output Control (bit 0) – Automatically set to push-pull
for a SYNC clock output and open-drain for a SYNC clock input.
VOUT_DROOP Command
The droop or load-line resistance is used as part of the current
sharing algorithm. When current sharing is enabled,
VOUT_DROOP is automatically set to a value of 0xBA80
(1.25m). The same droop value is used for both reference and
member devices.
Current Sharing Example
Example pin-strap resistor values for the current sharing group in
Figure 24 are shown in Table 34. Sequential SMBus addresses
are used with the reference device at the lowest address. The
reference device outputs the SYNC clock to the member devices
SYNC clock input. The devices are configured for 3-phase current
sharing with all phases enabled. The reference device soft-start
ramp time is at least 5ms and soft-start delay time is at least
10ms greater than the member devices for proper
synchronization and output voltage ramp.
TABLE 33. Current Sense Options
Current Sense Configuration Usage
Ground referenced, down slope
(RDS(ON) sensing)
Low duty cycle and low fSW
Vout referenced, down slope
(Inductor DCR sensing)
Low duty cycle and high fSW
Vout referenced, up slope
(Inductor DCR sensing)
High duty cycle
TABLE 34. Pin-Strap Current Sharing Resistor Values
Pin Reference Member_1 Member_2 Description
SA0, SA1 Low, Low Open, Low High, Low SMBus Address = 0x20 for Reference
SMBus Address = 0x21 for Member_1
SMBus Address = 0x22 for Member_2
CFG0 23.7k23.7k23.7kCurrent Share # of Members = 3
Current Share Control = Enabled
CFG1 High Low Low SYNC = Output for Reference
SYNC = Input for Member_1 and Member_2
CFG2 42.2k46.4k51.1kCurrent Share Position = 0 for Reference
Current Share Position = 1 for Member_1
Current Share Position = 2 for Member_2
SS 31.6k14.7k14.7kDelay = 15ms, Ramp = 5ms for Reference
Delay = 5ms, Ramp = 5ms for Member_1
Delay = 5ms, Ramp = 5ms for Member_2
PH_EN High High High All Phases Enabled
Reference
Position = 0
SMBus = 0x20
SYNC = Output
Delay = 15 ms
Ramp = 5 ms
Member_1
Position = 1
SMBus = 0x21
SYNC = Input
Delay = 5 ms
Ramp = 5 ms
Member_2
Position = 2
SMBus = 0x22
SYNC = Input
Delay = 5 ms
Ramp = 5 ms
FIGURE 25.
ZL2008
FN6859 Rev 4.00 Page 38 of 43
April 29, 2011
Related Tools and Documentation
The following application support documents and tools are
available to help simplify your design.
Ordering Information
PART NUMBER
(Notes 19, 20, 21) PART MARKING
TEMP RANGE
(°C) PACKAGE
PKG.
DWG. #
ZL2008ALBFT 2008 -40 to +85 36 Ld 6mmx6mm QFN L36.6x6A
ZL2008ALBFT1 2008 -40 to +85 36 Ld 6mmx6mm QFN L36.6x6A
NOTES:
19. Please refer to TB347 for details on reel specifications.
20. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte
tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil Pb-
free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
21. For Moisture Sensitivity Level (MSL), please see device information page for ZL2008. For more information on MSL please see techbrief TB363.
Item Description
AN2010 Application Note: Thermal and Layout Guidelines
AN2032 Application Note: NLR Configuration
AN2033 Application Note: PMBus Command Set
AN2034 Application Note: Current Sharing
AN2035 Application Note: Compensation Using CompZL
ZL2008
FN6859 Rev 4.00 Page 39 of 43
April 29, 2011
Revision History
Rev. # Description Date
1.0 Initial release January 2009
FN6859.0 Assigned file number FN6859 to datasheet as this will be the first release with an Intersil file number. Replaced header
and footer with Intersil header and footer. Updated disclaimer information to read “Intersil and it’s subsidiaries including
Zilker Labs, Inc.” No changes to datasheet content
February 2009
FN6859.1 Updated to new format. Updates include:
a) Putting Abs Max, Recommended Operating Conditions and Electrical Specs tables into Intersil format
- Adding Pb-free reflow link to Thermal info
- Adding Intersil's caution statement, per legal
b) Put Ordering Info table into Intersil format
- Adding Moisture Sensitivity Level note, TB347 tape and reel spec note and Pb-free note (corresponding to
lead finish).
c) Updated sales disclaimer on last page to Intersil's verbiage
d) Replaced Zilker POD with Intersil equivalent POD (L36.6x6A)
e) Updated graphics to Intersil standards (font change)
f) Updated cross references to tables (since table #s were removed from Electrical Specs, Abs Max, Recommended
Operating Conditions and Pin Descriptions tables)
g) Updated cross references to figures (since figure #s was removed from Pinout)
h) Added equation #s to all equations
i) Added Intersil standard over temp notes to Electrical Specs table as follows:
- Added Note 14: "Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified.
Temperature limits established by characterization and are not production tested." to MIN MAX columns of Electrical
Specs table.
-Added "Boldface limits apply over the operating temperature range, -40°C to +85°C" to common conditions of
Electrical Specs table. Bolded all MIN and MAX specs in table.
“Absolute Maximum Ratings” on page 4:
Removed “MOSFET Drive Reference for VR Pin……120mA”. Removed “2.5V Logic Reference for V25 Pin ……120mA”
“Electrical Specifications” table, page 4 to page 6:
Changed Max for IDDS Shutdown Current from 8mA to 9mA.
Changed conditions for “Vr Reference Output Voltage” from <50mA to <20mA
Changed conditions for “V25 Reference Output Voltage” from <50mA to <20mA
Added the following sentence to Note 8: “Current Share member minimum delay is 5ms. Current share reference must
be 10ms greater than member delay”
Added Note 15: “Limits established by characterization and are not production tested.” Added Note 15 callout to the
following parameters:
Soft start delay duration range for test condt using I2C
Minimum Sync Pulse Width
High-side Driver Peak Gate Drive Current (Pull-down)
High-side Driver Pull-up Resistance
High-side Driver Pull-down Resistance
Low-side Driver Pull-up Resistance
Low-side Driver Pull-down Resistance
Switching timing (for both conditions)
VTRK Tracking Ramp Accuracy
UVLO Delay
UVLO Hysteresis for I2C/SMBus conditions
Power Good Delay for I2C/SMBus conditions
VSEN Undervoltage Threshold for I2C/SMBus conditions
VSEN Overvoltage Threshold for I2C/SMBus conditions
VSEN Undervoltage/Overvoltage Fault Response Time for I2C/SMBus conditions
Current Limit Protection Delay for I2C/SMBus conditions
Temperature Compensation of Current Limit Protection Threshold for I2C/SMBus conditions
Thermal Protection Threshold (Junction Temperature) for I2C/SMBus conditions
October 2009
ZL2008
FN6859 Rev 4.00 Page 40 of 43
April 29, 2011
FN6859.1 Added Note 15: “Nominal capacitance of logic pins is 5pF”. Added Note 15 callouts to Logic Output Low, VOL and Logic
Output High, VOH parameters.
Changed “Logic Input Bias Current” parameter to “Logic Input Leakage Current”. Changed Logic Input Leakage Current
Min from -10µA to -250nA and Max from 10µA to 250nA.
Removed “MGN Input Bias Current” line from table.
Changed “Power Good VOUT Low Threshold” parameter to “Power Good VOUT Threshold” and removed “Power Good VOUT
High Threshold” line from table.
Page 10:
Removed 2 paragraphs as follows:
“The ZL2008 can be configured by simply connecting its pins according to the tables provided in the following sections…
I2C/SMBus interface using an available computer and the included USB cable.”
“Application notes and … local Zilker Labs sales office to order an evaluation kit”
Throughout: Changed all referenced Zilker App note numbers to newly assigned Intersil numbers (e.g. AN33 -> AN2033)
“Current Limit Threshold Selection” on page 21. In paragraph below Figure 16, changed “The current sensing method can
be selected via the I2C/SMBus interface.” to “The current sensing method can be selected using the CFG2 pin as shown
in Tables 26 and 28 or via the I2C/SMBus interface.” In 3rd paragraph below Figure 16, changed “This is to avoid taking
a reading just after a current load step” to “This is to avoid taking a reading just after a switching transition”. Added “Note
that IOUT_CAL_GAIN is set to 2m by default.” to end of last paragraph.
Added “(Voltage seen on 2m)” to Tables 14 and 15 captions on page 21.
Replaced Table 25. Phase Offset Pin-strap Settings on page 30 (changed “CFG2 Pin” column to “RCFG2” and added
“Current Sense” column).
Table 26. Phase Offset Resistor Settings on page 30. Added “Current Sense” column and RCFG2 rows from 42.2k through
162k and corresponding Phase Offset rows.
On page 30: 2nd column, 1st paragraph, changed “The phase offset of (multi-phase) current sharing devices is
automatically set to a value between 0° and 337.5° in 22.5° increments as follows: Phase Offset = SMBus Address[4:0]
–Current Share Position * 22.5°” to “The phase offset of a current sharing group is automatically set to a value between
0° and 337.5° in 22.5° increments as follows: Phase Offset = (SMBus Address[4:0] –Current Share Position) * 22.5°”
Added “The phase of the individual members in a group are spread evenly from the phase offset of the group.”
Table 28. Current Share Position Settings on page 33. Added “Current Sense” column. Added RCFG2 rows from 42.2k
through 82.5k and corresponding Current Share Position rows.
Removed former Table 35. Snapshot Parameters
“Snapshot Parameter Capture” on page 35. Added “See AN2033 for details on using the Snapshot in addition to the
parameters supported.” to 2nd paragraph
On page 4, corrected:
“Analog Input Voltages for ISENA Pin. . . . . . . . . . . . . . . . . . . . .1.5V to 30V”
to:
“Analog Input Voltages for ISENA Pin. . . . . . . . . . . . . . . . . . . .-1.5V to 6.5V”
On page 21, Table 14, added “DCR VLIM (mV)” column. Renamed “Threshold Voltage” column to “RDS VLIM”
On page 22, Table 15, added “DCR VLIM (mV)” column. Renamed “VLIM” column to “RDS VLIM”
On page 21, in second column, first paragraph, changed “Note that IOUT_CAL_GAIN is set to 2m by default.” to “By
default, the IOUT_CAL_GAIN is set to 1m for DCR mode and 2m for RDS mode.”
In Table 14 on page 21, removed “ (Voltage seen on 2m)” from caption
In Table 15 on page 22, removed “(Voltage seen on 2m)” from caption
October 2009
“Power Good” on page 16, changed 2nd sentence from “...if the output is within -10%/+15% of the target voltage.” to “...if
the output is within -10% of the target voltage.”
Replaced last paragraph in “Power Good” section.
“Fault Spreading” on page 31, added “or in sequencing order” to last sentence.
Change marketing part number to ZL2008ALBFT to note firmware revision.
November 2009
Revision History (Continued)
Rev. # Description Date
ZL2008
FN6859 Rev 4.00 Page 41 of 43
April 29, 2011
FN6859.2 Added “ESD Rating” on page 4. Added Note 1 to “ESD Rating” on page 4
Added “Latch Up (Tested per JESD78) 100mA” on page 4
Table 26 “Phase Offset Resistor Settings” on page 30, in third column titled "Current Sense", swapped RDS and DCR so
DCR is in the top part of the table and RDS in the bottom.
Added “About Intersil” on page 42
Corrected Note 2 in “Thermal Information” on page 4 from:
“JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech
Brief TB379 for details.”
To:
“JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct
attach” features. See Tech Brief TB379.”
In Table 28 on page 33, in the third column, swapped DCR and RDS so that RDS is on the bottom.
“Active Current Sharing” on page 31, second paragraph changed from "Figure 21 illustrates a typical ..." to "Figure 22
illustrates a typical ..."
On page 36, second column, changed from “Resistor pin-strap the CFG2 pin to set the following parameter:” change this
to say “Resistor pin-strap the CFG2 pin to set the current share position.”
April 2010
FN6859.3 Added following statement to disclaimer on page 42: “This product is subject to a license from Power One, Inc. related to
digital power technology as set forth in U.S. Patent No. 7,000,125 and other related patents owned by Power One, Inc.
These license rights do not extend to stand-alone POL regulators unless a royalty is paid to Power One, Inc.”
December 2010
FN6859.4 Updated to new template.
Removed Electrical specs notes 14 and 15:
14. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature
limits established by characterization and are not production tested.
15. Limits established by characterization and are not production tested.
and replaced with new Note 14: “Compliance to datasheet limits is assured by one or more methods: production test,
characterization and/or design.”
Page 1, 1st sentence, changed “The ZL2008 is a digital DC/DC controller with …” to “ZL20081 is a digital power controller
with…”
Page 4, Abs Max Ratings, the entry for Logic I/O pins, changed from "-0.3V to 6.5V" to "-0.3 to 6V"
Page 29, 2nd column, added sentence “Note that the SMBus address 0x4B is reserved for device test and cannot be used
in the system.” at the end of column two.
December 2010
Add the following lines to the“Recommended Operating Conditions” on page 4:
Input Voltage
VIN, Rise Time .. . . . . . . .5ms minimum
VIN Ramp . . . .. . . . . . . .Monotonic
Revision History (Continued)
Rev. # Description Date
FN6859 Rev 4.00 Page 42 of 43
April 29, 2011
ZL2008
Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted
in the quality certifications found at www.intersil.com/en/support/qualandreliability.html
Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such
modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are
current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its
subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Intersil or its subsidiaries. This product is subject to a license from Power One, Inc. related to digital power
technology as set forth in U.S. Patent No. 7,000,125 and other related patents owned by Power One, Inc. These license rights do not extend to stand-alone POL
regulators unless a royalty is paid to Power One, Inc.
For additional products, see www.intersil.com/en/products.html
© Copyright Intersil Americas LLC 2009-2011. All Rights Reserved.
All trademarks and registered trademarks are the property of their respective owners.
About Intersil
Intersil Corporation is a leader in the design and manufacture of high-performance analog, mixed-signal and power management
semiconductors. The company's products address some of the largest markets within the industrial and infrastructure, personal
computing and high-end consumer markets. For more information about Intersil, visit our website at www.intersil.com.
For the most updated datasheet, application notes, related documentation and related parts, please see the respective product
information page found at www.intersil.com. You may report errors or suggestions for improving this datasheet by visiting
www.intersil.com/en/support/ask-an-expert.html. Reliability reports are also available from our website at
http://www.intersil.com/en/support/qualandreliability.html#reliability
ZL2008
FN6859 Rev 4.00 Page 43 of 43
April 29, 2011
Package Outline Drawing
L36.6x6A
36 LEAD QUAD FLAT NO-LEAD PLASTIC PACKAGE
Rev 1, 9/09
located within the zone indicated. The pin #1 indentifier may be
Unless otherwise specified, tolerance : Decimal ± 0.05
Tiebar shown (if present) is a non-functional feature.
The configuration of the pin #1 identifier is optional, but must be
between 0.15mm and 0.30mm from the terminal tip.
Dimension b applies to the metallized terminal and is measured
Dimensions in ( ) for Reference Only.
Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
6.
either a mold or mark feature.
3.
5.
4.
2.
Dimensions are in millimeters.1.
NOTES:
BOTTOM VIEW
DETAIL "X"
SIDE VIEW
TYPICAL RECOMMENDED LAND PATTERN
TOP VIEW
( 4. 10 )
( 5. 60 TYP )
(36X 0.25 )
( 36X 0.80 )
( 36 X 0 . 50 )
0 . 00 MIN.
0 . 05 MAX.
0 . 2 REF
C
MAX 0.90
5
0.10 C
0.08 C
C
6.00
(4X) 0.15
6
PIN 1
INDEX AREA
6.00
B
A
4 .10 ± 0.10
36X 0.60 ± 0.10 36X 0.25
C0.10 M A B
4
19
18
9
10
PIN #1
27
28
36X
1
36
0.50 6
4.0
4X
INDEX AREA
Compliant to JEDEC MO-220VJJD.
7.
