MIC68200
2A Sequencing LDO with Trac king
and Ramp Control™
Ramp Control is a trademark of Micrel, Inc.
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2006
M9999-071206
(408) 955-1690
General Description
The MIC68200 is a high peak current LDO regulator
designed specifically for powering applications such
as FPGA core voltages that require high start up
current with lower nominal operating current. Capable
of sourcing 2A of current for start-up, the MIC68200
provides high power from a small MLF
®
leadless
package. The MIC68200 can also implement a variety
of power-up and power-down protocols such as
sequencing, tracking, and ratiometric tracking.
The MIC68200 operates from a wide input range of
1.65V to 5.5V, which includes all of the main supply
voltages commonly available today. It is designed to
drive digital circuits requiring low voltage at high
currents (i.e. PLDs, DSP, microcontroller, etc.). The
MIC68200 incorporates a delay pin (DLY) for control
of power on reset output (POR) at turn-on and power-
down delay at turn-off. In addition there is a ramp
control pin (RC) for either tracking applications or
output voltage slew rate adjustment at turn-on. This is
important in applications where the load is highly
capacitive and in-rush currents can cause supply
voltages to fail and microprocessors or other complex
logic chips to hang up.
Multiple MIC68200s can be daisy chained in two
modes. In tracking mode the output voltage of the
Master drives the RC pin of a Slave so that the Slave
tracks the main regulator during turn-on and turn-off.
In sequencing mode the POR of the Master drives the
enable (EN) of the Slave so that it turns on after the
Master and turns off before (or after) the Master. This
behavior is critical for power-up and power-down
control in multi-output power supplies. The MIC68200
is fully protected offering both thermal and current limit
protection and reverse current protection.
The MIC68200 has a junction temperature range of
–40°C to +125°C and is available in fixed as well as
an adjustable option. The MIC68200 is offered in the
tiny 10-pin 3mm x 3mm MLF
®
package.
Features
• Stable with 4.7µF ceramic capacitor
• Input voltage range: 1.65V to 5.5V
• 0.5V reference
• +
1.0% initial output tolerance
• 2A maximum output current – peak start up
• 1A Continuous Operating Current
• Tracking on turn-on and turn-off with pin
strapping
• Timing Controlled Sequencing On/Off
• Programmable Ramp Control™ for in-rush
current limiting and slew rate control of the
output voltage on Turn-On and Turn-Off
• Power-on Reset (POR) supervisor with
programmable delay time
• Single Master can control multiple Slave
regulators with tracking output voltages
• Tiny 3mm x 3mm MLF
®
package
• Maximum dropout (V
IN
– V
OUT
) of 500mV over
temperature at 1A output current
• Fixed and Adjustable Output Voltages
• Excellent line and load regulation specifications
• Logic controlled shutdown
• Thermal shutdown and current limit protection
Applications
• FPGA/PLD Power Supply
• Networking/Telecom Equipment
• Microprocessor Core Voltage
• High Efficiency Linear Post Regulator
• Sequenced or Tracked Power Supply
Micrel, Inc. MIC68200
July 2006
2 M9999-071206
(408) 955-1690
Typical Application
4.7µF
4.7µF
1nF
V
IN
= 3.3V
EN
MIC68200-1.8YML
IN OUT
EN SNS
RC
DLY GND POR
µProcessor
I/O
CORE
/RESET
2x
47KΩ
MIC68200-1.5YML
IN OUT
EN SNS
RC
DLY GND POR
10nF
0.7nF
0.6nF
U1
Master
U2
Slave
Sequenced Dual Power Supply for I/O and Core Voltage of µProcessor
U1.EN
U1.RC
U1.DLY
U1.OUT
U2.EN= U1.POR
U2.RC
U2.DLY
U2.OUT
U2.POR
U1.T
R
C
U1.T
DLY
U2.T
R
C
U2.T
DLY
U1.T
DLY
U2.T
DLY
U1 Full
y
Shut Down
U2 Full
y
Shut Down
Micrel, Inc. MIC68200
July 2006
3 M9999-071206
(408) 955-1690
4.7µF
4.7µF
10nF
V
IN
= 1.8V
EN
MIC68200-1.5YML
IN OUT
EN
RC
DELAY GND POR
µProcessor
I/O
CORE
/RESET
47K
Ω
10nF
MIC68200-1.2YML
IN OUT
EN
RC
DELAY GND POR
U1
Master
U2
Slave
Tracking Dual Power Supply for I/O and Core Voltage of µProcessor
U1.EN=U2.EN
U1.RC
U1.DLY
U2.RC=U1.OUT
U2.DLY
U2.OUT
U1.POR=U2.POR
U1.T
R
C
U2.T
DLY
U2.T
DLY
U1 Full
y
Shut Down
U2 Full
y
Shut Down
Micrel, Inc. MIC68200
July 2006
4 M9999-071206
(408) 955-1690
Block Diagram
Ordering Information
Part Number Marking
Code Output
Current
Voltage Junction
Temp. Range
Package
MIC68200-1.2YML ZC12 2.0A 1.2V –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
MIC68200-1.5YML ZC15 2.0A 1.5V –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
MIC68200-1.8YML ZC18 2.0A 1.8V –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
MIC68200-2.5YML ZC25 2.0A 2.5V –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
MIC68200-3.3YML ZC33 2.0A 3.3V –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
MIC68200YML ZAAA 2.0A ADJ –40°C to +125°C PB-Free 10-Pin 3x3 MLF
®
Note:
For additional voltage options, contact Micrel Marketing.
Micrel, Inc. MIC68200
July 2006
5 M9999-071206
(408) 955-1690
Pin Configuration
EP5
110
9
8
7
2
3
4
6
10-Pin 3mm × 3mm MLF (ML)
MIC68200-x.xYML (Fixed)
MIC68200YML (Adjustable)
Pin Description (Pin Numbering may change depending on layout considerations)
3x3 MLF-10
Fixed 3x3 MLF-10
Adjustable Pin Name
Pin Function
1,2 1,2 IN
Input: Input voltage supply pin. Place a capacitor to ground to
bypass the input supply
3 3 DLY
Delay: Capacitor to ground sets internal delay timer. Timer delays
power-on reset (POR) output at turn-on and ramp down at turn-off.
4 4 RC
Ramp Control: Voltage driven for tracking applications. Capacitor to
ground sets slew rate during start-up.
5 5 EN
Enable (Input): CMOS compatible input. Logic high = enable and
logic low = shutdown.
6, EP 6, EP GND Ground: EP is connected to ground on 3x3 MLF-10L.
7 7 POR
Power-on Reset: Open-drain output device indicates when the
output is in regulation. High (open) means device is regulating within
10%. POR onset can be delayed using a single capacitor from Delay
to ground.
8 8 SNS
Adjustable regulators: Feedback input. Connect to external resistor
voltage divider.
Fixed regulators: Sense pin. Connect to output at load for point-of-
load regulation.
9, 10 9,10 OUT Output Voltage: Output of voltage regulator. Place capacitor to
ground to bypass the output voltage. Minimum load current is 100uA.
Nominal bypass capacitor is 4.7uf ceramic.
Micrel, Inc. MIC68200
July 2006
6
M9999-071206
(408) 955-1690
Absolute Maximum Ratings(1)
Supply Voltage (V
IN
) ................................................ 6V
Enable Input Voltage (V
EN
).....................0 to V
IN +
0.3V
POR (V
POR
)...................................................V
IN
+ 0.3V
RC ...............................................................V
IN
+ 0.3V
Power Dissipation...........................Internally Limited
(3)
Junction Temperature ................ –40°C ≤ T
J
≤ +125°C
Storage Temperature (T
S
).......... –65°C ≤ T
J
≤ +150°C
ESD Rating
(4)
........................................................ 2KV
Operating Ratings(2)
Supply voltage (V
IN
) .................................1.65V to 5.5V
Enable Input Voltage (V
EN
).............................. 0V to V
IN
Ramp Control (V
RC
).......................................0V to 5.5V
Junction Temperature Range ......–40°C ≤ T
J
≤ +125°C
Package Thermal Resistance
3x3 MLF-10 (θ
JA
) ...................................... 60°C/W
Electrical Characteristics(5)
T
A
= 25°C with V
IN
= V
OUT
+ 1V; V
EN
= V
IN
; I
OUT
= 10mA;
bold
values indicate –40°C ≤ T
J
≤ +125°C, unless noted.
Parameter Conditions Min Typ Max Units
Output Voltage Accuracy 10mA < I
OUT
< I
L(max)
, V
OUT
+ 1 ≤ V
IN
≤ 5.5V -2 +2 %
Feedback Voltage Adjustable version only 0.49 0.50 0.51 V
Feedback Current Adjustable version only 10 nA
Output Voltage Line Regulation V
IN
= V
OUT
+ 1V to 5.0V 0.06 0.5 V
Output Voltage Load Regulation I
L
= 0mA to 2A 0.3 1 %
V
IN
– V
O
; Dropout Voltage I
L
= 500mA
I
L
= 1.0A
I
L
= 2.0A
140
200
300
250
400
600
mV
mV
mV
Ground Pin Current I
L
= 10mA
I
L
= 500mA
I
L
= 1.0A
I
L
= 2.0A
1.5
7
15
42
15
30
80
mA
mA
mA
mA
Shutdown Current V
EN
= 0V; V
OUT
= 0V 0.01 10 µA
Current Limit V
OUT
= 0V; V
IN
= 3.0V 2.0 3.4 6.0 A
Start-up Time V
EN
= V
IN
; C
RC
= Open 25 150 µs
Enable Input
Enable Input Threshold Regulator enable
Regulator shutdown
1
0.2 V
V
Enable Hysteresis 50 100 250 mV
Enable Input Current V
IL
≤ 0.2V (Regulator shutdown)
V
IH
≤ 1V (Regulator enable)
0.8
2
µA
µA
POR Output
I
POR(LEAK)
V
POR
= 5.5V; POR = High 1
2 µA
µA
V
POR(LO)
Output Logic-Low Voltage (undervoltage condition),
I
POR
= 1mA
60
90 mV
7.5 10 12.5 % V
POR
: V
OUT
Ramping Up
V
OUT
Ramping Down Threshold, % of V
OUT
below nominal 10 12.5 15 %
Delay Current V
DELAY
= 0.75V 0.7 1 1.3 µA
Delay Voltage (Note 6) V
POR
= High 1.185 1.235 1.285 V
Micrel, Inc. MIC68200
July 2006
7
M9999-071206
(408) 955-1690
Parameter Conditions Min Typ Max Units
Ramp Control
I
RC
Ramp Control Current 0.7 1 1.3 µA
I
DISCHARGE(OUTPUT)
(Note 7) V
OUT
= 0.5V
REF
, V
RAMP
=0V 25 45 70 mA
Tracking Accuracy: Fixed
(
Note 8)
200mV < V
RC
< V
TARGET ;
Measure
(VOUT – V
RC
) -50 25 100 mV
Tracking Accuracy: Adjustable
(
Note 8)
Measure
(VOUT -
V
RC
x (V
TARGET
/ 500mV)) 2 15 50 mV
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any T
A
(ambient temperature) is P
D(max)
= T
J(max)
– T
A
) / θ
JA
. Exceeding the maximum allowable
power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
5. Specification for packaged product only.
6. Timer High Voltage along with Delay pin current (1µA nom) determines the delay per uF of capacitance. Typical delay is 1.1sec/µf
7. Discharge current is the current drawn from the output to ground to actively discharge the output capacitor during the shutdown process.
8. V
TARGET
is the output voltage of an adjustable with customer resistor divider installed between VOUT and Adj/Sns pin, or the rated output
voltage of a fixed device.
Micrel, Inc. MIC68200
July 2006
8
M9999-071206
(408) 955-1690
Typical Characteristics
0
5
10
15
20
25
30
35
40
45
Ground Current
vs. Output Current
0.0 2.0
OUTPUT CURRENT (A)
0.4 0.8 1.2 1.6
V
IN
= V
OUT
+ 1V
V
OUT
= 1.8V
C
OUT
= 10µF
0
0.5
1
1.5
2
012345
INPUT VOLTAGE (V)
Output Voltage
vs. Input Voltage
V
IN
= V
OUT
+ 1V
V
OUT
= 1.8V
C
OUT
= 10µF
I
OUT
= 10mA
0
50
100
150
200
250
300
350
400
Dropout Voltage
vs. Output Current
0.0 2.0
OUTPUT CURRENT (mA)
0.4 0.8 1.2 1.6
V
IN
= V
OUT
+ 1V
V
OUT
= 1.8V
C
OUT
= 10µF
1.60
1.65
1.70
1.75
1.85
1.90
1.95
2.00
Output Voltage
vs. Temperature
20 40 60 80
TEMPERATURE (°C)
1.80
V
IN
= V
OUT
+ 1V
V
OUT
= 1.8V
C
OUT
= 10µF
0.4
0.5
0.6
0.7
0.8
0.9
1
1.9 2.4 2.9 3.4 3.9 4.4 4.9 5.4
INPUT VOLTAGE (V)
Enable Threshold
vs. Input Voltage
V
OUT
= 1.8V
I
OUT
= 10mA
C
OUT
= 10µF
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
Current Limit
vs. Input Voltage
V
IN
= 2.8V
V
OUT
= 1.8V
C
OUT
= 10µF
3.9
4.0
0.001
0.01
0.1
1
1
FREQUENCY (kHz)
Output Noise
Spectral Density
0.10.01 10 100 1,000 10,000
V
IN
= V
OUT
+1V
V
OUT
= 1.8V
C
OUT
= 10µF
Micrel, Inc. MIC68200
July 2006
9
M9999-071206
(408) 955-1690
Functional Characteristics
Micrel, Inc. MIC68200
July 2006
10
M9999-071206
(408) 955-1690
Applications Information
Enable Input
The MIC68200 features a TTL/CMOS compatible
positive logic enable input for on/off control of the
device. High (>1V) enables the regulator while low
(<.2V) disables the regulator. In shutdown the
regulator consumes very little current (only a few
microamperes of leakage). For simple applications the
enable (EN) can be connected to V
IN
(IN). While
MIC68200 only requires a few µA’s of enable current
to turn on, actual enable pin current will depend on the
overdrive (voltage exceeding 1V) in each particular
application.
Enable Connections for Logic Driven input
IN
EN
OUT
POR
GND
MIC68200-1.8BML
4.7µF
RC
10nF
DLY
IN
EN
OUT
POR
GND
MIC68200-1.5BML
RC
DLY
4.7µF
1nF
V
IN
= 3.3V
Control Logic
High > 1V
Enable Connection for V
IN
-Driven and/or Slow
Risetime Inputs
IN
EN
OUT
POR
GND
MIC68200-1.8YML
4.7µF
RC
10nF
DLY
IN
EN
OUT
POR
GND
MIC68200-1.5YML
RC
DLY
4.7µF
1nF
V
IN
= 3.3V
10K
Ω
10n
F
~ 1V/mSec
Input Capacitor
An input capacitor of 0.1µF or greater is
recommended when the device is more than 4 inches
away from the bulk supply capacitance, or when the
supply is a battery. Small, surface mount chip
capacitors can be used for the bypassing. The
capacitor should be place within 1 inch of the device
for optimal performance. Larger values will help to
improve ripple rejection by bypassing the regulator
input, further improving the integrity of the output
voltage.
Output Capacitor
The MIC68200 requires an output capacitor for stable
operation. As a µCap LDO, the MIC68200 can
operate with ceramic output capacitors of 4.7µF or
greater with ESR’s ranging from a 3mΩ to over
300mΩ. Values of greater than 4.7µF improve
transient response and noise reduction at high
frequency. X7R/X5R dielectric-type ceramic
capacitors are recommended because of their
superior temperature performance. X7R-type
capacitors change capacitance by 15% over their
operating temperature range and are the most stable
type of ceramic capacitors. Larger output
capacitances can be achieved by placing tantalum or
aluminum electrolytics in parallel with the ceramic
capacitor. For example, a 100µF electrolytic in parallel
with a 4.7µF ceramic can provide the transient and
high frequency noise performance of a 100µF ceramic
at a significantly lower cost. Specific
undershoot/overshoot performance will depend on
both the values and ESR/ESL of the capacitors.
U1
Master
U2
Slave
U1
Master
U2
Slave
Micrel, Inc. MIC68200
July 2006
11
M9999-071206
(408) 955-1690
Adjustable Regulator Design
R1
OUT
SNS
R2
0.5V
C
OUT
4.7µF
*C
FF
0.1µF
*Required only for large
values of R1 and R2.
Adjustable Regulator with Resistors
The adjustable MIC68200 output voltage can be
programmed from 0.5V to 5.5V using a resistor divider
from output to the SNS pin. Resistors can be quite
large, up to 1MΩ because of the very high input
impedance and low bias current of the sense
amplifier. Typical sense input currents are less than
30nA which causes less than 0.3% error with R1 and
R2 less than or equal to 100KΩ. For large value
resistors (>50K) R1 should be bypassed by a small
capacitor (C
FF
= 0.1µF bypass capacitor) to avoid
instability due to phase lag at the ADJ/SNS input.
The output resistor divider values are calculated by:
⎟
⎠
⎞
⎜
⎝
⎛+= 1
R2
R1
0.5V
OUT
V
Power on Reset (POR) and Delay (DLY)
The power-on reset output (POR) is an open-drain
N-Channel device requiring a pull-up resistor to either
the input voltage or output voltage for proper voltage
levels. POR is driven by the internal timer so that the
release of POR at turn-on can be delayed for as much
as 1 second. POR is always pulled low when enable
(EN) is pulled low or the output goes out of regulation
by more than 10% due to loading conditions.
The internal timer is controlled by the DLY pin which
has a bidirectional current source and two limiting
comparators. A capacitor connected from DLY to
GND sets the delay time for two functions. On start
up, DLY sets the time from power good to the release
of the POR. At shut down, the delay sets the time
from disable (EN pin driven low) to actual ramp down
of the output voltage. The current source is +/-1µA,
which charges the capacitor from ~150mV (nominal
disabled DLY voltage) to ~1.25V. At turn on, the DLY
cap begins to charge when the output voltage reaches
90% of the target value. When the capacitor reaches
1.25V, the output of the POR is released to go high.
At turn off, the DLY cap begins to discharge when the
EN is driven low. When the cap reaches ~150mV the
output is ramped down. Both delays are nominally the
same, and are calculated by the same formula:
()
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=A1
C
1.1T
DLY
DLY
µ
Scale Factor is:
1.1 seconds/microfarad,
1.1 milliseconds/nanofarad, or
1.1 microseconds/picofarad.
T
DLYOFF
is the time from lowering of EN to the start of
ramp down on the off cycle. T
POR
is the time from
raising of EN to the release (low to high edge) of the
POR. This behavior means that a µP or other
complex logic system is guaranteed that power has
been good for a known time before the POR is
released, and they are further guaranteed that once
POR is pulled low, they have a known time to ‘tidy up’
memory or other registers for a well controlled
shutdown. In Master/Slave configurations the timers
can be used to assure that the Master is always
accurately regulating when the Slave is on.
Ramp Control
The ramp control (RC) has a bidirectional current
source and a sense amplifier, which together are used
to control the voltage at the output. When RC is below
the target voltage (nominal output voltage for fixed
voltage parts, 0.5V for adjustable parts) the RC pin
controls the output voltage. When RC is at or above
the target voltage, the output is controlled by the
internal regulator.
Tracking Applications: Driving RC from a Voltage
Source
Fixed Parts: If RC is driven from another (Master)
regulator the two outputs will track each other until the
Master exceeds the target voltage of the Slave
regulator. Typically the output of the MIC68200 will
track above the RC input by 30mV to 70mV. This
offset is designed to allow Master/Slave tracking of
same-voltage regulators. Without the offset, same-
voltage Master/Slave configurations could suffer poor
regulation.
Adjustable Parts: The RC pin on adjustable versions
operates from 0V to 0.5V. To implement tracking on
an adjustable version, an external resistor divider
must be used. This divider is the nearly same ratio as
the voltage setting divider used to drive the Sense/Adj
pin. It is recommended that the ratio be adjusted to
track ~50mV (2% to 3%) above the target voltage if
the Master and Slave are operating at the same target
voltage.
Micrel, Inc. MIC68200
July 2006
12 M9999-071206
(408) 955-1690
Ramp Up: Cap Controlled Slew Rate
If a capacitor is connected to RC, the bidirectional
current source will charge the cap during startup and
discharge the cap during shutdown. The size of the
capacitor and the RC current (1µA nom) control the
slew rate of the output voltage during startup. For
example, to ramp up a 1.8V regulator from zero to full
output in 10mSec requires a 5.6nF capacitor.
For Fixed Versions:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=A1
C
VT
RC
OUTRC
µ
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
RC
ON
C
A1
SR
µ
Similarly, to slew an adjustable (any output voltage)
from 0 to full output in 10mSec requires a 20nF cap.
For Adjustable Versions:
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=A1
C
V5.0T
RC
RC
µ
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
RC
OUTON
C
A1
2VSR
µ
Ramp Down: Turn Off Slew Rate
When EN is lowered and the DLY pin has discharged,
the RC pin and the OUT pin slew toward zero. For
fixed voltage devices, the RC pin slew rate is 2 to 3
times the SR
ON
defined above. For adjustable voltage
devices the RC pin slew is much higher. In both
cases, turn off slew rate may be determined by the
RC pin for low values of output capacitor, or by the
maximum discharge current available at the output for
large values of output capacitor. Turn off slew rate is
not a specified characteristic of the MIC68200.
Sequencing Configurations
Sequencing refers to timing based Master/Slave
control between regulators. It allows a Master device
to control the start and stop timing of a single or
multiple Slave devices. In typical sequencing the
Master POR drives the Slave EN. The sequence
begins with the Master EN driven high. The Master
output ramps up and triggers the Master DLY when
the Master output reaches 90%. The Master DLY then
determines when the POR is released to enable the
Slave device. When the Master EN is driven low, the
Master POR is immediately pulled low causing the
Slave to ramp down. However, the Master output will
not ramp down until the Master DLY has fully
discharged. In this way, the Master power can remain
good after the Slave has been ramped down.
In sequencing configurations the Master DLY controls
the turn-on time of the Slave and the Slave DLY
controls the turn-off time of the Slave.
Sequencing Connections
IN
EN
OUT
POR
GND
MIC68200-1.8YML
CDlyM
RC
DLY
IN
EN
OUT
POR
GND
MIC68200-1.2YML
RC
DLY
4.7
µ
F
V
IN
= 2.5V
CDlyS
I/O
µProcesso
r
Core
/RESET
4.7
µ
F
EN
10K
10K
U1
Master
U2
Slave
Delayed Sequencing
CDlyS > CDlyM
[CDlyS=2nF; CDlyM=1nF]
Windowed Sequencing
CDlyS < CDlyM
[CDlyS=1nF; CDlyM=2nF]
Micrel, Inc.
MIC68200
July 2006 13
M9999-071206
(408) 955-1690
Tracking Configurations
Normal Tracking
In normal tracking the Slave RC pin is driven from the
Master output. The internal control buffering assures
that the output of the Slave is always slightly above
the Master to guarantee that the Slave properly
regulates (based on its own internal reference) if
Master and Slave are both fixed voltage devices of the
same output voltage. The schematic and plot below
show a 1.2 volt device tracking a 1.8 volt device
through the entire turn-on / turn-off sequence. Note
that since the RC pin will overdrive the target voltage
(to assure proper regulation) the ramp down delay is
longer than the POR delay during turn-on.
Fixed Voltage Devices
4.7µF
4.7µF
V
IN
= 2.5V
EN
MIC68200-1.8YML
IN OUT
EN SNS
RC
DLY GND POR
10K
MIC68200-1.2YML
IN OUT
EN SNS
RC
DLY GND POR
1nF
1nF
V
OUT1
V
OUT2
PO
R
NC
U1
Master
U2
Slave
Fixed voltage versions of MIC68200 have two internal
voltage dividers: one for setting the output voltage and
the other for driving the tracking circuitry. Adjustable
parts have up to two external dividers: one from
output to SNS (to set the output voltage) and one from
the output to the Slave RC pin (in tracking
configurations). Also, the RC pin in fixed parts
operates at the same voltage as the output, whereas
the RC pin in adjustable parts operates at the 0.5V
reference. To setup a normal tracking configuration,
the divider driving the Slave RC pin is the same ratio
(or nearly the same – if both Master and Slave are set
to the same output voltage, the Slave RC divider
should be adjusted 2% to 4% higher) as the divider
driving the Slave SNS pin. This is shown below.
Adjustable Voltage devi ces
4.7µF
4.7µF
V
IN
= 3.3V
EN
MIC68200YML
IN OUT
EN SNS
RC
DLY GND POR
10K
MIC68200YML
IN OUT
EN SNS
RC
DLY GND POR
10.0K 1.0K
2.50K 383Ω
10.0K
3.83K
V
OUT1
V
OUT2
PO
R
NC
2nF
1nF
U1
Master
U2
Slave
Micrel, Inc.
MIC68200
July 2006 14
M9999-071206
(408) 955-1690
Ratiometric Tracking
Ratiometric tracking allows independent ramping
speeds for both regulators so that the regulation
voltage is reached at the same time. This is
accomplished by adding a resistor divider between the
Master output pin and the Slave RC pin. The divider
should be scaled such that the Slave RC pin reaches
or exceeds the target output voltage of the Slave as
the Master reaches its target voltage.
Fixed Voltage Devices
4.7µF
4.7µF
V
IN
= 2.5V
EN
MIC68200-1.8YML
IN OUT
EN SNS
RC
DLY GND POR
10K
1nF 1K
1.5K
1nF
MIC68200-1.2YML
IN OUT
EN SNS
RC
DLY GND POR
V
OUT1
V
OUT2
PO
R
NC
U1
Master
U2
Slave
Ratiometric tracking may be used with adjustable
parts by simply connecting the RC pins of the Master
and Slave. Use a single RC capacitor of twice the
normal value (since twice the current is injected into
the single RC cap). Alternatively, adjustable parts
may use ratiometric tracking in a manner similar to
standard tracking, with the tracking divider changed to
the same resistor ratio driving the Master Adj/Sns pin.
Adjustable Voltage Devices
4.7µF
4.7µF
V
IN
= 3.3V
EN
MIC68200YML
IN OUT
EN SNS
RC
DLY GND POR
10K
Ω
MIC68200YML
IN OUT
EN SNS
RC
DLY GND POR
10.0K
2.5K
3.83K
10.0K
3nF
1nF
NC
V
OUT1
V
OUT2
PO
R
U1
Master
U2
Slave
Final Note on Tracking
The MIC68200 does not fully shutdown until the output load is discharged to near zero. If RC is driven from an external source in
a tracking configuration, and the external source does not go to zero on shutdown it may prevent complete shutdown of the
MIC68200. This will cause no damage, but some Q current will remain and may cause concern in battery operated portable
equipment. Also, when RC is driven in tracking mode, pulling EN low will not cause the output to drop. Maintaining low EN in
tracking mode simply means that the MIC68200 will shutdown when the tracking voltage gets near zero. In no case can the
MIC68200 enter the tracking mode unless EN is pulled high.
Micrel, Inc.
MIC68200
July 2006 15
M9999-071206
(408) 955-1690
Package Information
10-Pin 3mm x 3mm MLF (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for
its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a
product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for
surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant
injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk
and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
© 2005 Micrel, Inc.
