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ADP2370 Datasheet
(ADP2370 / ADP2371) Low Quiescent Current Buck Regulator

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Data Sheet
High Voltage, 1.2 MHz/600 kHz, 800 mA,
Low Quiescent Current Buck Regulator
ADP2370/ADP2371
FEATURES
Input voltage range: 3.2 V to 15 V, output current: 800 mA
Quiescent current < 14 µA in power saving mode (PSM)
>90% efficiency
Force PWM pin (SYNC), 600 kHz/1.2 MHz frequency pin
(FSEL)
Fixed outputs: 0.8 V, 1.2 V, 1.5 V, 1.8 V, 2.5 V, 3.0 V, 3.3 V, 5 V,
and adjustable option
100% duty cycle capability
Initial accuracy: ±1%
Low shutdown current: <1.2 µA
Quick output discharge (QOD) option
Synchronizable to an external clock
8-lead, 0.75 mm × 3 mm × 3 mm LFCSP (QFN) package
Supported by ADIsimPower design tool
APPLICATIONS
Portable and battery-powered equipment
Automatic meter readers (WSN)
Point of sales and transaction processing instruments
Medical instruments
Medium format display tablets and pads
GENERAL DESCRIPTION
The ADP2370/ADP2371 are high efficiency, low quiescent current,
800 mA buck (step-down) dc-to-dc converters in small 8-lead,
3 mm × 3 mm LFCSP (QFN) packages. The total solution requires
only three tiny external components.
The buck regulator uses a proprietary high speed current mode,
constant frequency PWM control scheme for excellent stability
and transient response. The need for an external rectifier is elimi-
nated by using a high efficiency synchronous rectifier architecture.
To ensure the longest battery life in portable applications, the
ADP2370/ADP2371 employ a power saving variable frequency
mode that reduces the switching frequency under light load
conditions. The ADP2370/ADP2371 operate from input voltages
of 3.2 V to 15 V allowing the use of multiple alkaline/NiMH,
lithium cells, or other standard power sources.
The ADP2370/ADP2371 offer multiple options for setting the
operational frequency. The ADP2370/ADP2371 can be synchro-
nized to a 600 kHz to 1.2 MHz external clock or it can be forced
to operate at 600 kHz or 1.2 MHz via the FSEL pin. The ADP2370/
ADP2371 can be forced to operate in PWM mode (FPWM)
when noise considerations are more important than efficiency.
VIN = 6V
CIN
10µF
TYPICAL APPLICATION CIRCUIT
VIN
1
ADP2370/
ADP2371
PGND
8
POWER GOOD
1.2MHz
600kHz
FSEL 2
ON
OFF
EN
3
SYNC
4
AGND
(EXPOSED PAD)
7 SW
PG
6
FB
5
VOUT = 3.3V
COUT
10µF
Figure 1.
A power-good output is available to indicate when the output
voltage is below 92% of its nominal value.
The ADP2371 is identical to the ADP2370 except that the
ADP2371 includes the addition of an integrated switched
resistor, quick output discharge function (QOD) that auto-
matically discharges the output when the device is disabled.
Both devices include an internal power switch and a synchronous
rectifier for minimal external part count and high efficiency.
The ADP2370/ADP2371 also include internal soft start and
internal compensation for ease of use.
During a logic controlled shutdown, the input is disconnected
from the output and the regulator draws less than 1.2 μA from
the input source. Other key features include undervoltage lockout
to prevent deep battery discharge and soft start to prevent input
overcurrent at startup. Short-circuit protection and thermal over-
load protection circuits prevent damage under adverse conditions.
The ADP2370/ADP2371 each use one 0805 capacitor, one 1206
capacitor, and one 4 mm × 4 mm inductor. The total solution
size is about 53 mm2 resulting in a very small footprint solution
to meet a variety of portable applications.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2012 Analog Devices, Inc. All rights reserved.
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ADP2370 Datasheet
(ADP2370 / ADP2371) Low Quiescent Current Buck Regulator

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ADP2370/ADP2371
TABLE OF CONTENTS
Features .............................................................................................. 1 
Applications....................................................................................... 1 
Typical Application Circuit ............................................................. 1 
General Description ......................................................................... 1 
Revision History ............................................................................... 2 
Specifications..................................................................................... 3 
Recommended Specifications: Capacitors ................................ 5 
Absolute Maximum Ratings ....................................................... 6 
Thermal Data ................................................................................ 6 
Thermal Resistance ...................................................................... 6 
ESD Caution.................................................................................. 6 
Pin Configuration and Function Descriptions............................. 7 
Typical Performance Characteristics ............................................. 8 
Buck Output .................................................................................. 8 
Theory of Operation ...................................................................... 20 
PWM Operation......................................................................... 20 
PSM Operation ........................................................................... 21 
Features Descriptions..................................................................... 22 
Precision Enable ......................................................................... 22 
Forced PWM or PWM/PSM Selection.................................... 22 
Quick Output Discharge (QOD) Function............................. 22 
Short-Circuit Protection............................................................ 22 
REVISION HISTORY
5/12—Rev. 0 to Rev. A
Changed Voltage Range for SW to PGND and Ground Plane
from −0.3 V to VIN + 0.3 V to −0.7 V to VIN + 0.3 V ............... 6
Changes to Ordering Guide .......................................................... 32
4/12—Revision 0: Initial Version
Data Sheet
Undervoltage Lockout ............................................................... 22 
Thermal Protection.................................................................... 22 
Soft Start ...................................................................................... 22 
Current Limit.............................................................................. 22 
100% Duty Cycle ........................................................................ 23 
Synchronizing ............................................................................. 23 
Power Good ................................................................................ 24 
Applications Information .............................................................. 25 
ADIsimPower Design Tool ....................................................... 25 
External Component Selection ................................................ 25 
Selecting the Inductor................................................................ 25 
Output Capacitor........................................................................ 25 
Input Capacitor........................................................................... 25 
Adjustable Output Voltage Programming .............................. 25 
Efficiency..................................................................................... 26 
Recommended Buck External Components .......................... 26 
Capacitor Selection .................................................................... 28 
Thermal Considerations................................................................ 29 
PCB Layout Considerations...................................................... 30 
Packaging and Ordering Information ......................................... 32 
Outline Dimensions................................................................... 32 
Ordering Guide .......................................................................... 32 
Rev. A | Page 2 of 32
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ADP2370 Datasheet
(ADP2370 / ADP2371) Low Quiescent Current Buck Regulator

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Data Sheet
ADP2370/ADP2371
SPECIFICATIONS
VIN = VOUT + 1 V or 3.2 V, whichever is greater, EN = VIN, IOUT = 100 mA, CIN = 10 μF, COUT = 10 µF, TA = 25°C for typical specifications,
TJ = −40°C to +125°C for minimum/maximum specifications, unless otherwise noted.
Table 1.
Parameter
SUPPLY
Input Voltage Range
Quiescent Current
Shutdown Current
FIXED OUTPUT
Output Current
Fixed Output Accuracy
Symbol
VIN
IQ-PSM
IQ-PWM
ISW-PWM
ISHUT
IOUT
VOUT
ADJUSTABLE OUTPUT
Feedback Voltage
Feedback Voltage Accuracy
Output Voltage Range
FIXED AND ADJUSTABLE OUTPUT
Load Regulation
Line Regulation
Efficiency
Overcurrent Frequency Foldback Threshold
Rising
Falling
PSM Threshold
Feedback Pin Input Current
Fixed
Adjustable
Minimum On Time
VFB
VFB-TOL
VOUT-ADJ
∆VOUT/∆IOUT
∆VOUT/∆VIN
EFF
OCFOLDBACK-RISE
OCFOLDBACK-FALL
PSMTHRESHOLD
IFB-FIXED
IFB-ADJUST
ON-TIMEMIN
Soft Start Time
Active Pull-Down Resistance
(ADP2371)
POWER SWITCH
P-Channel On Resistance
SSTIME
RPULL-DOWN
RDSON-P
N-Channel On Resistance
RDSON-N
Current Limit
P-Channel
N-Channel
Leakage Current
P-Channel
N-Channel
OSCILLATOR
Oscillator Frequency
ILIM-P
ILIM-N
ILEAK-SW
fOSC
Test Conditions/Comments
FSEL = VIN, SYNC = 0 V, no load, device not
switching
FSEL = VIN, SYNC = VIN, no load, device not
switching
FSEL = VIN, SYNC = VIN, no load, device switching
EN = GND, TJ = −40°C to +85°C
Initial set point, IOUT = 250 mA, TJ = 25°C
IOUT = 250 mA
No load to full load, PWM mode
Initial set point, IOUT = 250 mA, TJ = 25°C
No load to full load
No load to full load
IOUT = 250 mA
IOUT = 250 mA, VIN = 7.2 V, VOUT = 3.3 V
% of VOUT, VOUT rising
% of VOUT, VOUT falling
VIN = 7.2 V, VOUT = 3.3 V
Fixed output voltage model
Adjustable output voltage model
VIN < 5.5 V
VIN > 5.5 V
When EN rises from 0 V to VIN, and VOUT = 0.9 × VOUT
VIN > 5.5 V, IOUT = 400 mA
VIN < 5.5 V, IOUT = 400 mA
VIN > 5.5 V, IOUT = 400 mA
VIN < 5.5 V, IOUT = 400 mA
Peak inductor current
Peak inductor current
FSEL = VIN, 3.2 V ≤ VIN ≤ 15 V
FSEL = 0 V, 3.2 V ≤ VIN ≤ 15 V
Min
3.2
800
−1
−1.5
−3
−1
0.8
1.0
500
Typ Max Unit
15
13.5
725
5.7
1.2 3.5
V
μA
μA
mA
μA
mA
+1 %
+1.5 %
+3 %
0.8 V
+1 %
14 V
0.125
0.01
92
%/A
%/V
%
50 %
37.5 %
170 mA
2.5 μA
10 nA
65 100 ns
40 60 ns
350 μs
260 400 Ω
400 mΩ
500 mΩ
280 mΩ
400 mΩ
1200 1300 mA
500 550 mA
0.01 1
0.01 1
μA
μA
1.2 1.4 MHz
600 700 kHz
Rev. A | Page 3 of 32
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ADP2370 datasheets pdf
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