Compact, 800 mA, 3 MHz,
Simple DVS, Buck Regulator
ADP2147
Rev. 0
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FEATURES
Input voltage: 2.3 V to 5.5 V
Peak efficiency: 95%
3 MHz fixed frequency operation
Low quiescent current: 23 μA
Ultralow shutdown current: 0.2 μA (typical)
VSEL pin for simple dynamic voltage scaling (DVS)
100% duty cycle low dropout mode
Internal synchronous rectifier, compensation, and soft start
Current overload and thermal shutdown protection
Small, 6-ball, 1 mm × 1.5 mm WLCSP package
APPLICATIONS
PDAs and palmtop computers
Wireless handsets
Digital audio portable media players
Digital cameras, GPS navigation units
Low power portable medical equipment
GENERAL DESCRIPTION
The ADP2147 is a high efficiency, low quiescent current, step-
down (buck) dc-to-dc regulator with an output voltage that can
be switched between two different settings under the control of
a select pin. The total solution requires only three tiny external
components.
The buck regulator automatically switches operating modes,
depending on the load current level, to maximize efficiency. At
high output loads, the buck regulator operates in PWM mode.
When the load current falls below a predefined threshold, the
regulator operates in power save mode (PSM), improving the
light-load efficiency.
The ADP2147 runs on input voltages of 2.3 V to 5.5 V, which
allows for single lithium or lithium polymer cells, multiple
alkaline or NiMH cells, PCMCIA, USB, and other standard
power sources. The maximum load current of 800 mA is
achievable across the input voltage range.
The ADP2147 is available with fixed output voltages from 0.8 V
to 3.3 V. All versions include an internal power switch and
synchronous rectifier for minimal external part count and high
efficiency. The ADP2147 has an internal soft start and is
internally compensated. During logic controlled shutdown, the
input is disconnected from the output, and the ADP2147 draws
less than 0.2 A (typical) from the power source.
Other key features include undervoltage lockout to prevent deep
battery discharge and soft start to prevent input current over-
shoot at startup. The ADP2147 is available in a 6-ball WLCSP.
TYPICAL APPLICATIONS CIRCUIT
ON
OFF
V
OUT
_H
V
OUT
_L
VIN SW
EN
VSEL
GND
VOUT
ADP2147
4.7µF 4.7µF
2.3V TO 5.5V V
OUT
1.0µH
09885-001
Figure 1.
ADP2147
Rev. 0 | Page 2 of 16
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
General Description......................................................................... 1
Typical Applications Circuit............................................................ 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Input and Output Capacitor, Recommended
Specifications ................................................................................ 3
Absolute Maximum Ratings............................................................ 4
Thermal Data ................................................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics ............................................. 6
Theory of Operation ...................................................................... 11
Control Scheme .......................................................................... 11
PWM Mode................................................................................. 11
Power Save Mode........................................................................ 11
Enable/Shutdown ....................................................................... 11
Simple Dynamic Voltage Scaling (DVS) ................................. 12
Short-Circuit Protection............................................................ 12
Undervoltage Lockout ............................................................... 12
Thermal Protection.................................................................... 12
Soft Start ...................................................................................... 12
Current Limit.............................................................................. 12
100% Duty Operation................................................................ 12
Applications Information.............................................................. 13
External Component Selection ................................................ 13
Thermal Considerations............................................................ 14
PCB Layout Guidelines.............................................................. 14
Evaluation Board ............................................................................ 15
Evaluation Board Layout........................................................... 15
Outline Dimensions ....................................................................... 16
Ordering Guide .......................................................................... 16
REVISION HISTORY
5/11—Revision 0: Initial Version
ADP2147
Rev. 0 | Page 3 of 16
SPECIFICATIONS
VIN = 3.6 V, VOUT = 0.8 V to 3.3 V, TJ = −40°C to +125°C for minimum/maximum specifications, and TA = 25°C for typical specifications,
unless otherwise noted. All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
INPUT CHARACTERISTICS
Input Voltage Range 2.3 5.5 V
Undervoltage Lockout Threshold VIN rising 2.3 V
V
IN falling 2.00 2.15 2.25 V
OUTPUT CHARACTERISTICS
Output Voltage Accuracy PWM mode, VSEL = Low −2 +2 %
PWM mode, VSEL = High −2.5 +2.5 %
Line Regulation VIN = 2.3 V to 5.5 V, PWM mode 0.25 %/V
Load Regulation ILOAD = 0 mA to 800 mA −0.95 %/A
PWM TO POWER SAVE MODE CURRENT THRESHOLD 100 mA
INPUT CURRENT CHARACTERISTICS
DC Operating Current ILOAD = 0 mA, device not switching 23 30 A
Shutdown Current EN = 0 V, TA = TJ = −40°C to +85°C 0.2 1.0 A
SW CHARACTERISTICS
SW On Resistance pFET 155 240 mΩ
nFET 115 200 mΩ
Current Limit pFET switch peak current limit 1100 1500 1650 mA
ENABLE/VSEL CHARACTERISTICS
Input High Threshold 1.2 V
Input Low Threshold 0.4 V
Input Leakage Current EN = VSEL = 0 V to 3.6 V −1 0 +1 A
OSCILLATOR FREQUENCY 2.6 3.0 3.4 MHz
START-UP TIME 250 s
THERMAL CHARACTERISTICS
Thermal Shutdown Threshold 150 °C
Thermal Shutdown Hysteresis 20 °C
INPUT AND OUTPUT CAPACITOR, RECOMMENDED SPECIFICATIONS
TA = −40°C to +125°C, unless otherwise specified. All limits at temperature extremes are guaranteed via correlation using standard
statistical quality control (SQC).
Table 2.
Parameter Symbol Min Typ Max Unit
MINIMUM INPUT AND OUTPUT CAPACITANCE CMIN 4.7 µF
CAPACITOR ESR RESR 0.001 1 Ω
ADP2147
Rev. 0 | Page 4 of 16
ABSOLUTE MAXIMUM RATINGS
Table 3.
Parameter Rating
VIN, EN, VSEL −0.4 V to +6.5 V
VOUT, SW to GND −1.0 V to (VIN + 0.2 V)
Temperature Range
Operating Ambient −40°C to +85°C
Operating Junction −40°C to +125°C
Storage Temperature −65°C to +150°C
Lead Temperature Range −65°C to +150°C
Soldering (10 sec) 300°C
Vapor Phase (60 sec) 215°C
Infrared (15 sec) 220°C
ESD Model
Human Body ±1500 V
Charged Device ±500 V
Machine ±100 V
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. These are stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL DATA
Absolute maximum ratings apply individually only, not in
combination.
The ADP2147 can be damaged if the junction temperature limit is
exceeded. Monitoring ambient temperature does not guarantee
that the junction temperature (TJ) is within the specified
temperature limit. In applications with high power dissipation
and poor thermal resistance, the maximum ambient temperature
may need to be derated. In applications with moderate power
dissipation and low printed circuit board (PCB) thermal
resistance, the maximum ambient temperature can exceed the
maximum limit if the junction temperature is within specification
limits. The junction temperature (TJ) of the device is dependent
on the ambient temperature (TA), the power dissipation of the
device (PD), and the junction-to-ambient thermal resistance of the
package (θJA). Maximum junction temperature (TJ) is calculated
from the ambient temperature (TA) and power dissipation (PD)
using the following formula:
TJ = TA + (PD × θJA)
Junction-to-ambient thermal resistance (θJA) of the package is
based on modeling and calculation using a 4-layer board. The
junction-to-ambient thermal resistance is highly dependent on
the application and board layout. In applications where high
maximum power dissipation exists, close attention to thermal
board design is required. The value of θJA may vary, depending on
PCB material, layout, and environmental conditions. The specified
values of θJA are based on a 4-layer, 4 in. × 3 in. circuit board. Refer
to JEDEC JESD 51-9 for detailed information pertaining to board
construction. For additional information, see the AN-617
Application Note, MicroCSP™ Wafer Level Chip Scale Package.
ΨJB is the junction-to-board thermal characterization parameter
measured in units of °C/W. The package ΨJB is based on modeling
and calculation using a 4-layer board. The JESD51-12, Guidelines
for Reporting and Using Package Thermal Information, states that
thermal characterization parameters are not the same as thermal
resistances. ΨJB measures the component power flowing through
multiple thermal paths rather than through a single path, which
is the procedure for measuring thermal resistance, θJB. There-
fore, ΨJB thermal paths include convection from the top of the
package as well as radiation from the package, factors that make
ΨJB more useful in real-world applications than θJB. Maximum
junction temperature (TJ) is calculated from the board temperature
(TB) and power dissipation (PD) using the formula:
TJ = TB + (PD × ΨJB)
Refer to JEDEC JESD51-8 and JESD51-12 for more detailed
information about ΨJB.
THERMAL RESISTANCE
θJA and ΨJB are specified for the worst-case conditions, that is, a
device soldered in a circuit board for surface-mount packages.
Table 4. Thermal Resistance
Package Type θJA Ψ
JB Unit
6-Ball WLCSP 170 80 °C/W
ESD CAUTION
ADP2147
Rev. 0 | Page 5 of 16
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
VIN EN
SW
GND VOUT
VSEL
TOP VIEW
(BALL SIDE DOWN)
Not to Scale
ADP2147
1
A
B
C
2
BALL A1
INDICATOR
09885-002
Figure 2. Pin Configuration (Top View)
Table 5. Pin Function Descriptions
Pin No. Mnemonic Description
A1 VIN Power Source Input. VIN is the source of the pFET high-side switch. Bypass VIN to GND with a 4.7 µF or greater
capacitor as close to the ADP2147 as possible.
B1 SW Switch Node Output. SW is the drain of the P-channel MOSFET switch and N-channel synchronous rectifier.
Connect the output LC filter between SW and the output voltage.
C1 GND Ground. Connect the input and output capacitors to GND.
A2 EN Buck Activation. To turn on the buck, set EN to high. To turn off the buck, set EN to low.
B2 VSEL Voltage Select Input for Simple Dynamic Voltage Scaling (DVS). Drive VSEL low to switch the VOUT pin to the
default voltage setting. Drive VSEL high to switch VOUT to the alternate voltage setting.
C2 VOUT Output Voltage Sensing Input.
ADP2147
Rev. 0 | Page 6 of 16
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 3.6 V, TA = 25°C, VEN = VIN, unless otherwise noted.
100
90
80
70
60
50
40
30
20
10
0
0.001 0.01 0.1 1
IOUT (A)
EFFICIENCY (%)
VIN = 2.3V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
09885-003
Figure 3. Efficiency vs. Load Current, Across Input Voltage,
VOUT = 1.8 V
100
90
80
70
60
50
40
30
20
10
0
0.001 0.01 0.1 1
IOUT (A)
EFFICIENCY (%)
VIN = 2.3V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
09885-005
Figure 4. Efficiency vs. Load Current, Across Input Voltage,
VOUT = 0.8 V
100
90
80
70
60
50
40
30
20
10
0
0.001 0.01 0.1 1
I
OUT
(A)
EFFICIENCY (%)
V
IN
= 3.9V
V
IN
= 4.2V
V
IN
= 5.5V
09885-007
Figure 5. Efficiency vs. Load Current, Across Input Voltage,
VOUT = 3.3 V
1.825
1.775
1.785
1.795
1.805
1.815
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
I
OUT
(A)
V
OUT
(V)
V
IN
= 2.3V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
09885-006
Figure 6. Load Regulation Across Input Voltage, VOUT = 1.8 V
0.815
0.810
0.805
0.800
0.795
0.790
0.785
0.780
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
I
OUT
(A)
V
OUT
(V)
V
IN
= 2.3V
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 5.5V
09885-008
Figure 7. Load Regulation Across Input Voltage, VOUT = 0.8 V
3.378
3.338
3.358
3.318
3.298
3.278
3.258
3.238
3.218
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
I
OUT
(A)
V
OUT
(V)
V
IN
= 3.9V
V
IN
= 4.2V
V
IN
= 5.5V
09885-009
Figure 8. Load Regulation Across Input Voltage, VOUT = 3.3 V
ADP2147
Rev. 0 | Page 7 of 16
3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.6
2.7
2.5
0.10.20.30.40.50.60.7
I
OUT
(A)
FREQUENCY (MHz)
+25°C
+85°C
+125°C
–40°C
09885-010
Figure 9. Frequency vs. Output Current, Across Temperature,
VOUT = 1.8 V
3.5
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.6
2.7
2.5
0.10.20.30.40.50.60.7
IOUT (A)
FREQUENCY (MHz)
VIN = 2.3V
VIN = 3.6V
VIN = 4.2V
VIN = 5.5V
09885-011
Figure 10. Frequency vs. Output Current, Across Supply Voltage,
VOUT = 1.8 V
2.3 2.8 3.3 3.8 4.3 4.8 5.3
INPUT VOLTAGE (V)
90
80
70
60
50
40
30
20
10
0
OUTPUT VOLTAGE (mV)
I
OUT
= 100µA
I
OUT
= 25mA
I
OUT
= 500mA
09885-034
Figure 11. Output Voltage Ripple vs. Input Voltage,
Across Output Current, VOUT = 1.8 V
2.3 2.8 3.3 3.8 4.3 4.8 5.3
INPUT VOLTAGE (V)
350
300
250
200
150
100
50
0
R
DSON
(mΩ)
–40°C
+25°C
+125°C
09885-036
Figure 12. RDSON PFET vs. Input Voltage, Across Temperature
2.3 2.8 3.3 3.8 4.3 4.8 5.3
INPUT VOLTAGE (V)
250
200
150
100
50
0
R
DSON
(mΩ)
–40°C
+25°C
+125°C
09885-037
Figure 13. RDSON NFET vs. Input Voltage, Across Temperature
T
4
4
1
1
2
M 40.0µs A CH2 215mA
T 26.00%
CH1 100mV
CH4 5.00V
CH2 250mA Ω
SW
VOUT
IOUT
09885-014
Figure 14. Response to Load Transient, 150 mA to 500 mA,
VOUT = 1.8 V
ADP2147
Rev. 0 | Page 8 of 16
T
4
4
1
1
2
M 40.0µs A CH2 215mA
T 26.00%
CH1 100mV
CH4 5.00V
CH2 250mA Ω
SW
VOUT
IOUT
09885-015
Figure 15. Response to Load Transient, 50 mA to 200 mA,
VOUT = 1.8 V
T
4
4
1
1
2
M 40.0µs A CH2 215mA
T 26.00%
CH1 100mV
CH4 5.00V
CH2 250mA Ω
SW
V
OUT
I
OUT
09885-016
Figure 16. Response to Load Transient, 150 mA to 500 mA,
VOUT = 0.8 V
CH1 100mV
CH4 5.00V
CH2 100mA ΩM 40.0µs A CH2 134mA
1
4
T 26.00%
T
1
4
2
SW
VOUT
IOUT
09885-017
Figure 17. Response to Load Transient, 50 mA to 200 mA, VOUT = 0.8 V
T
4
4
1
1
2
M 40.0µs A CH2 275mA
T 26.00%
CH1 100mV
CH4 5.00V
CH2 250mA Ω
SW
V
OUT
I
OUT
09885-018
Figure 18. Response to Load Transient, 150 mA to 500 mA,
VOUT = 3.3 V
T
4
4
1
1
2
M 40.0µs A CH2 114mA
T 26.00%
CH1 100mV
CH4 5.00V
CH2 100mA Ω
SW
V
OUT
I
OUT
09885-019
Figure 19. Response to Load Transient, 50 mA to 200 mA,
VOUT = 3.3 V
CH1 20.0mV
CH3 1.00V
M 40.0µs A CH3 4.50V
T
1
3
T –84.0000µs
V
OUT
V
IN
09885-020
Figure 20. Response to Line Transient, VOUT = 3.3 V, VIN = 4.0 V to 4.8 V
ADP2147
Rev. 0 | Page 9 of 16
CH1 20.0mV
CH3 1.00V
M 40.0µs A CH3 4.50V
T
1
3
T –84.0000µs
VOUT
VIN
09885-021
Figure 21. Response to Line Transient, VOUT = 0.8 V,
VIN = 4.0 V to 4.8 V
CH1 20.0mV
CH3 1.00V
M 40.0µs A CH3 4.50V
T
1
3
T –84.0000µs
VOUT
VIN
09885-033
Figure 22. Response to Line Transient, VOUT = 1.8 V,
VIN = 4.0 V to 4.8 V
CH1 2.00V Ω
CH4 5.00V
CH2 500mA ΩM 40.0µs A CH3 2.50V
T 10.40%
CH3 5.00V
T
4
1
1
1
3
2
SW
VOUT
IIN
EN
09885-022
Figure 23. Startup, VOUT = 1.8 V, IOUT = 10 mA
CH1 1.00V Ω
CH4 5.00V
CH2 500mA ΩM 40.0µs A CH3 2.50V
T 10.40%
CH3 5.00V
T
4
1
1
1
3
2
SW
VOUT
IIN
EN
09885-023
Figure 24. Startup, VOUT = 0.8 V, IOUT = 10 mA
CH1 5.00V Ω
CH4 5.00V
CH2 500mA ΩM 40.0µs A CH3 2.50V
T 10.40%
CH3 5.00V
T
4
1
1
1
3
2
SW
VOUT
IIN
EN
09885-024
Figure 25. Startup, VOUT = 3.3 V, IOUT = 10 mA
T
4
4
1
1
2
ACH1 3.80mVM 1.00µs
T 50.00%
CH1 10.0mVΩ
CH4 2.00V
CH2 500mA Ω
SW
V
OUT
I
L
09885-025
Figure 26. Typical Waveform, VOUT = 1.8 V, PSM Mode, IOUT = 10 mA
ADP2147
Rev. 0 | Page 10 of 16
T
4
1
1
2
ACH4 1.32VM 40.0µs
T 50.00%
CH1 10.0mVΩCH2 500mA Ω
CH4 2.00V
SW
VOUT
IL
09885-026
Figure 27. Typical Waveform, VOUT = 1.8 V, PWM Mode, IOUT = 200 mA
130
0
10
20
30
40
50
60
70
80
90
100
110
120
0.001 0.01 0.1 1
I
OUT
(A)
V
OUT
RIPPLE (mV)
1.8V, V
IN
= 5.5V, AUTO
1.8V, V
IN
= 3.6V, AUTO
1.8V, V
IN
= 2.3V, AUTO
09885-028
Figure 28. VOUT Peak-to-Peak Ripple vs. Output Current, VOUT = 1.8 V
T
1
2
A CH2 1.72VM 40.0µs
CH1 100mV CH2 2.00V
T –1.966µs
09885-129
Figure 29. VSEL Change Triggering VOUT Transition from 0.981 V to 1.275 V,
ILOAD = 10 mA
T
1
2
A CH2 1.72VM 40.0µs
CH1 100mV CH2 2.00V
T 79.64µs
09885-130
Figure 30. VSEL Change Triggering VOUT Transition from 1.275 V to 0.981 V,
ILOAD = 10 mA
T
1
2
A CH2 1.76VM 40.0µs
CH1 100mV CH2 2.00V
T 50.20%
09885-131
Figure 31. VSEL Change Triggering VOUT Transition from 0.981 V to1.275 V,
ILOAD = 200 mA
T
1
2
A CH2 1.76VM 40.0µs
CH1 100mV CH2 2.00V
T 30.00%
09885-132
Figure 32. VSEL Change Triggering VOUT Transition from1.275 V to 0.981 V, ILOAD
= 200 mA
ADP2147
Rev. 0 | Page 11 of 16
THEORY OF OPERATION
I
LIMIT
LOW
CURRENT
PSM
COMP
SOFT START
UNDERVOLTAGE
LOCKOUT
THERMAL
SHUTDOWN
DRIVER
AND
ANTISHOOT-
THROUGH
OSCILLATOR
PWM
COMP
GM ERROR
AMP
ADP2147
VOUT
VSEL
GND
EN
SW
VIN
09885-027
PWM/
PSM
CONTROL
Figure 33. Functional Block Diagram
The ADP2147 is a step-down dc-to-dc regulator that uses a
fixed frequency and high speed current-mode architecture.
The high switching frequency and tiny 6-ball WLCSP package
enable a small step-down dc-to-dc regulator solution.
The ADP2147 operates with an input voltage of 2.3 V to 5.5 V
and regulates an output voltage down to 0.8 V.
CONTROL SCHEME
The ADP2147 operates with a fixed frequency, current-mode
PWM control architecture at medium to high loads for high
efficiency but shifts to a power save mode control scheme at
light loads to lower the regulation power losses. When operating in
PWM mode, the duty cycle of the integrated switches is adjusted
and regulates the output voltage. When operating in power save
mode at light loads, the output voltage is controlled in a hyster-
etic manner, with higher VOUT ripple. During part of this time,
the converter is able to stop switching and enters an idle mode,
which improves conversion efficiency.
PWM MODE
In PWM mode, the ADP2147 operates at a fixed frequency of
3 MHz, set by an internal oscillator. At the start of each oscillator
cycle, the pFET switch is turned on, sending a positive voltage
across the inductor. Current in the inductor increases until the
magnitude of the current sense signal crosses the peak inductor
current threshold. This turns off the pFET switch and turns on the
nFET synchronous rectifier, which sends a negative voltage across
the inductor, causing the inductor current to decrease. The
synchronous rectifier stays on for the rest of the cycle.
The ADP2147 regulates the output voltage by adjusting the peak
inductor current threshold.
POWER SAVE MODE
The ADP2147 smoothly transitions to the power save mode of
operation when the load current decreases below the power
save mode current threshold. When the ADP2147 enters power
save mode, an offset is induced in the PWM regulation level,
which makes the output voltage rise. When the output voltage
reaches a level approximately 1.5% above the PWM regulation
level, PWM operation turns off. At this point, both power
switches are off, and the ADP2147 enters idle mode. COUT
discharges until VOUT falls to the PWM regulation voltage, at
which point the device drives the inductor to cause VOUT to rise
again to the upper threshold. This process is repeated for as long as
the load current is below the power save mode current
threshold.
Power Save Mode Current Threshold
The power save mode current threshold is set to 100 mA. The
ADP2147 employs a scheme that ensures that this current is
accurately controlled and independent of VIN and VOUT levels.
The control scheme also ensures that there is very little hysteresis
between the power save mode current threshold and that of the
PWM mode. The power save mode current threshold is opti-
mized for excellent efficiency across all load currents.
ENABLE/SHUTDOWN
The ADP2147 starts operating with soft start when the EN pin
is toggled from logic low to logic high. Pulling the EN pin low
forces the device into shutdown mode, reducing the supply
current to 0.2 A (typical).
ADP2147
Rev. 0 | Page 12 of 16
SIMPLE DYNAMIC VOLTAGE SCALING (DVS)
The ADP2147 has a VSEL pin that allows the user to force the
output voltage to change from one level (the default VOUT
setting) when VSEL is low and to another level (the alternate
VOUT setting) when VSEL is high. Transition between VOUT
levels is achieved within 40 µs when VOUT is commanded to go
from a lower voltage to a higher voltage. When VOUT is com-
manded to go from a higher VOUT voltage to a lower one, the
transition time depends on the load current present at that time.
SHORT-CIRCUIT PROTECTION
The ADP2147 includes frequency foldback to prevent output
current runaway on a hard short. When the voltage at the
feedback pin falls below half the target output voltage, indi-
cating the possibility of a hard short at the output, the switching
frequency is reduced to half the internal oscillator frequency.
The reduction in the switching frequency allows more time for
the inductor to discharge, preventing a runaway of output current.
UNDERVOLTAGE LOCKOUT
To protect against battery discharge, undervoltage lockout
(UVLO) circuitry is integrated on the ADP2147. If the input
voltage drops below the 2.15 V UVLO threshold, the ADP2147
shuts down, and both the power switch and the synchronous
rectifier turn off. When the voltage rises above the UVLO
threshold, the soft start period is initiated, and the part is
enabled.
THERMAL PROTECTION
In the event that the ADP2147 junction temperature rises above
150°C, the thermal shutdown circuit turns off the regulator.
Extreme junction temperatures can be the result of high current
operation, poor circuit board design, or high ambient temperature.
A 20°C hysteresis is included so that when thermal shutdown
occurs, the ADP2147 does not return to operation until the on-
chip temperature drops below 130°C. When coming out of
thermal shutdown, a soft start is initiated.
SOFT START
The ADP2147 has an internal soft start function that ramps the
output voltage in a controlled manner upon startup, thereby
limiting the inrush current. The soft start minimizes input
voltage drop when a battery or a high impedance power source is
connected to the regulator’s input.
After the EN pin is driven high, internal circuits begin to power
up. Start-up time in the ADP2147 is the measure of when the
output is in regulation after the EN pin is driven high. Start-up
time consists of the power-up time plus the soft start time.
CURRENT LIMIT
The ADP2147 has protection circuitry to limit the amount of
positive current flowing through the PFET switch and the
synchronous rectifier. The positive current limit on the power
switch controls the amount of current that can flow from the
power source to the output. The negative current limit prevents
the inductor current from reversing direction and flowing out
of the load.
100% DUTY OPERATION
With a drop in VIN or with an increase in ILOAD, the ADP2147
eventually reaches a limit where, even with the pFET switch on
100% of the time, VOUT drops below the desired output voltage.
At this limit, the ADP2147 smoothly transitions to a mode
where the PFET switch stays on 100% of the time. When the input
conditions change again and the required duty cycle falls, the
ADP2147 immediately restarts PWM regulation without
allowing overshoot on VOUT.
ADP2147
Rev. 0 | Page 13 of 16
APPLICATIONS INFORMATION
EXTERNAL COMPONENT SELECTION
Trade-offs between performance parameters such as efficiency
and transient response can be made by varying the choice of
external components in the applications circuit, as shown in
Figure 1.
Inductor
The high switching frequency of the ADP2147 allows for the
selection of small chip inductors. For best performance, use
inductor values between 0.7 H and 3 H. Recommended
inductors are shown in Table 6.
The peak-to-peak inductor current ripple is calculated using
the following equation:
LfV
VVV
I
SW
IN
OUT
IN
OUT
RIPPLE ××
−×
=)(
where:
fSW is the switching frequency.
L is the inductor value.
The minimum dc current rating of the inductor must be greater
than the inductor peak current. The inductor peak current is
calculated using the following equation:
2
)(
RIPPLE
MAXLOAD
PEAK
I
II +=
Inductor conduction losses are caused by the flow of current
through the inductor, which has an associated internal DCR.
Larger sized inductors have smaller DCR, which may decrease
inductor conduction losses. Inductor core losses are related to
the magnetic permeability of the core material. Because the
ADP2147 is a high switching frequency dc-to-dc regulator,
shielded ferrite core material is recommended for its low core
losses and low electromagnetic interference (EMI). Table 6
shows the suggested inductors that can be used for different
output current requirements; several inductors are also listed to
minimize PCB space for small current applications.
Table 6. Suggested 1.0 μH Inductors
Vendor Model
Dimensions
(mm)
ISAT
(mA)
DCR
(mΩ)
Murata LQM2MPN1R0NG0B 2.0 × 1.6 × 0.9 1400 85
LQM18PN1R0 1.6 × 0.8 × 0.33 700 52
Coilcraft® EPL2014-102ML 2.0 × 2.0 × 1.4 900 59
0603LS-102 1.8 × 1.27 × 1.1 400 81
Toko MDT2520-CN 2.5 × 2.0 × 1.2 1800 100
TDK GLFR1608T1R0M-LR 1.6 × 0.8 × 0.8 360 80
Taiyo Yuden CBMF1608T1R0M 1.6 × 0.8 × 0.8 290 90
Output Capacitor
Increasing the value of the output capacitor reduces the output
voltage ripple and improves load transient response. When
choosing the capacitor value, it is also important to account for
the loss of capacitance due to dc output voltage bias.
Ceramic capacitors are manufactured with a variety of dielectrics,
each with different behavior over temperature and applied voltage.
Capacitors must have a dielectric adequate to ensure the
minimum capacitance over the necessary temperature range
and dc bias conditions. X5R or X7R dielectrics with a voltage
rating of 6.3 V or 10 V are recommended for best performance.
Y5V and Z5U dielectrics are not recommended for use with any
dc-to-dc regulator because of their poor temperature and dc bias
characteristics.
The worst-case capacitance, accounting for capacitor variation
over temperature, component tolerance, and voltage, is
calculated using the following equation:
CEFF = COUT × (1 − TEMPCO) × (1 − TOL)
where:
CEFF is the effective capacitance at the operating voltage.
TEMPCO is the worst-case capacitor temperature coefficient.
TOL is the worst-case component tolerance.
In this example, the worst-case temperature coefficient (TEMPCO)
over −40°C to +85°C is assumed to be 15% for an X5R dielectric.
The tolerance of the capacitor (TOL) is assumed to be 10%, and
COUT is 4.0466 F at 1.8 V, as shown in Figure 34.
Substituting these values in the equation yields
CEFF = 4.0466 F × (1 − 0.15) × (1 − 0.1) = 3.0956 F
To guarantee the performance of the ADP2147, it is imperative
that the effects of dc bias, temperature, and tolerances on the
behavior of the capacitors be evaluated for each application.
6
5
4
3
2
1
0
0123456
DC BIAS VOLTAGE (V)
CAPACITANCE (µF)
09885-029
Figure 34. Typical Capacitor Performance
The peak-to-peak output voltage ripple for the selected output
capacitor and inductor values is calculated using the following
equation:
()
OUT
SW
IN
RIPPLE CLf
V
V××××
=22
π
OUT
SW
RIPPLE
Cf
I
××
=8
ADP2147
Rev. 0 | Page 14 of 16
Capacitors with lower equivalent series resistance (ESR) are
preferred to guarantee low output voltage ripple, as shown in
the following equation:
RIPPL
E
RIPPLE
COUT I
V
ESR ≤
The effective capacitance needed for stability, which includes
temperature and dc bias effects, is 3 µF.
Table 7. Suggested 4.7 μF Capacitors
Vendor Type Model
Case
Size
Voltage
Rating (V)
Murata X5R GRM188R60J475 0603 6.3
Taiyo Yuden X5R JMK107BJ475 0603 6.3
TDK X5R C1608X5R0J475 0603 6.3
Input Capacitor
Higher value input capacitors help to reduce the input voltage
ripple and improve transient response. Maximum input
capacitor current is calculated using the following equation:
IN
OUT
IN
OUT
MAXLOAD
CIN V
VVV
II )(
)(
−
≥
To minimize supply noise, place the input capacitor as close to
the VIN pin of the ADP2147 as possible. As with the output
capacitor, a low ESR capacitor is recommended. The list of
recommended capacitors is shown in Table 8.
Table 8. Suggested 4.7 μF Capacitors
Vendor Type Model
Case
Size
Voltage
Rating (V)
Murata X5R GRM188R60J475 0603 6.3
Taiyo Yuden X5R JMK107BJ475 0603 6.3
TDK X5R C1608X5R0J475 0603 6.3
THERMAL CONSIDERATIONS
Because of the high efficiency of the ADP2147, only a small
amount of power is dissipated inside the ADP2147 package, which
reduces thermal constraints of the design.
However, in applications with maximum loads at high ambient
temperature, low supply voltage, and high duty cycle, the heat
dissipated in the package is high enough that it may cause the
junction temperature of the die to exceed the 125°C maximum.
If the junction temperature exceeds 150°C, the converter enters
thermal shutdown. The regulator recovers when the junction
temperature falls below 130°C.
The junction temperature of the die is the sum of the ambient
temperature of the environment and the temperature rise of the
package due to power dissipation, as shown in the following
equation:
TJ = TA + TR
where:
TJ is the junction temperature.
TA is the ambient temperature.
TR is the rise in temperature of the package due to power
dissipation.
The package’s rise in temperature is directly proportional to the
power dissipation in the package. The proportionality constant
for this relationship is the thermal resistance from the junction
of the die to the ambient temperature, as shown in the following
equation:
TR = θJA × PD
where:
TR is the rise in temperature of the package.
θJA is the thermal resistance from the junction of the die to the
ambient temperature of the package.
PD is the power dissipation in the package.
PCB LAYOUT GUIDELINES
Poor layout can affect the ADP2147 performance, causing EMI
and electromagnetic compatibility problems, ground bounce,
and voltage losses. Poor layout can also affect regulation and
stability. To implement a good layout, use the following rules:
• Place the inductor, input capacitor, and output capacitor
close to the IC using short tracks. These components carry
high switching frequencies, and large tracks act as antennas.
• Route the output voltage path away from the inductor and
SW node to minimize noise and magnetic interference.
• Maximize the size of ground metal on the component side
to help with thermal dissipation.
• Use a ground plane with several vias connecting to the com-
ponent side ground to further reduce noise interference on
sensitive circuit nodes.
ADP2147
Rev. 0 | Page 15 of 16
EVALUATION BOARD
VIN
VIN
GND
TB1 TB3
TB4
TB5
B1 21
C2
A1
C1
A2
B2
EN
VIN VOUT
GND OUT
G
ND IN
VIN
GND
SW
EN
VSEL
VOUT COUT
4.7µF
CIN
4.7µF
L1
1µH
U1
ADP2147
V
IN GND
CONN PWR 2-P
J6
VIN
2
1
3
2
1
3
2
1
JP3
ENABLE
3
2
1
3
2
1
JP2
VSEL
09885-030
Figure 35. Evaluation Board Schematic
EVALUATION BOARD LAYOUT
09885-136
Figure 36. Top Layer
09885-137
Figure 37. Bottom Layer
ADP2147
Rev. 0 | Page 16 of 16
OUTLINE DIMENSIONS
12-07-2010-A
A
B
C
0.640
0.595
0.550
0.370
0.355
0.340
0.270
0.240
0.210
1.070
1.030
0.990
1.545
1.505
1.465
12
BOTTOM VIEW
(BALL SIDE UP)
TOP VIEW
(BALL SIDE DOWN)
SIDE VIEW
0.340
0.320
0.300
1.00
REF
0.50
REF
BALL A1
IDENTIFIER
SEATING
PLANE
0.50 REF
COPLANARITY
0.05
Figure 38. 6-Ball Wafer Level Chip Scale Package [WLCSP]
(CB-6-12)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Temperature
Range
VOUT (V)
(VSEL = 0)
VOUT (V)
(VSEL = 1) Package Description
Package
Option Branding
ADP2147ACBZ-110-R7 −40°C to +125°C 1.275 0.981 6-Ball Wafer Level Chip Scale Package [WLCSP] CB-6-12 LLE
ADP2147ACBZ-130-R7 −40°C to +125°C 0.9 1.3 6-Ball Wafer Level Chip Scale Package [WLCSP] CB-6-12 LLF
ADP2147ACBZ-150-R7 −40°C to +125°C 1.2 1.0 6-Ball Wafer Level Chip Scale Package [WLCSP] CB-6-12 LLG
ADP2147ACBZ-170-R7 −40°C to +125°C 0.9 1.1 6-Ball Wafer Level Chip Scale Package [WLCSP] CB-6-12 LLH
ADP2147CB-110EVALZ Evaluation Board
ADP2147CB-130EVALZ Evaluation Board
ADP2147CB-150EVALZ Evaluation Board
ADP2147CB-170EVALZ Evaluation Board
1 Z = RoHS Compliant Part.
©2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09885-0-5/11(0)
