Analog Devices ADP3051 Datasheet
500 mA PWM Step-Down DC-DC with
FEATURES
Current mode control for simple loop compensation
Input voltage range: 2.7 V to 5.5 V
Output voltage range: 0.8 V to 5.5 V
Tri-Mode™ operation for high efficiency
550 kHz PWM operating frequency
High accuracy over line, load, and temperature
Micropower shutdown mode
Space-saving MSOP-8 package
APPLICATIONS
Li-ion powered handhelds
MP3 players
PDAs and palmtops
Consumer electronics
Synchronous Rectifier
ADP3051
GENERAL DESCRIPTION
The ADP3051 is a low noise, current mode, pulse width modulator (PWM) step-down converter capable of supplying over
500 mA to output voltages as low as 0.8 V. This device integrates
a low resistance power switch and synchronous rectifier, providing excellent efficiency over the entire output voltage range and
eliminating the need for a large and costly external Schottky
rectifier. Its 550 kHz switching frequency permits the use of
small external components.
Current mode control and external compensation allow the
regulator to be easily optimized for a wide range of operating
conditions. The ADP3051 operates at a constant 550 kHz
frequency at medium to heavy loads; it smoothly transitions
into Tri-Mode operation to save power at light loads. A pincontrolled micropower shutdown mode is also included.
The ADP3051’s 2.7 V to 5.5 V input operating range makes it
ideal for both battery-powered applications as well as those with
3.3 V or 5 V supply buses. It is available in a space-saving, 8-lead
MSOP package.
TYPICAL APPLICATION CIRCUIT
V
IN
10µF
3.3V
10kΩ
270pF
27pF
ADP3051
4
IN
SHDN
7
6
COMP FB
PGND GND
28
Figure 1.
SW
10µH
3
12.5kΩ
5
10kΩ
V
1.8V
OUT
10µF
04768-0-001
Rev. 0
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However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or 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. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
www.analog.com
ADP3051
TABLE OF CONTENTS
Specifications..................................................................................... 3
Undervoltage L ockout (UVLO) ............................................... 10
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configuration and Function Descriptions............................. 5
Typical Performance Characteristics............................................. 6
Theory of Operation ........................................................................ 9
PWM Control Mode.................................................................... 9
Tri-Mode Operation..................................................................... 9
100% Duty Cycle Operation ..................................................... 10
Shutdown..................................................................................... 10
REVISION HISTORY
6/04—Revision 0: Initial Version
Short-Circuit Protection and Recovery................................... 10
Applications..................................................................................... 11
Recommended Components .................................................... 11
Design Procedure....................................................................... 11
Output Capacitor Selection....................................................... 12
Circuit Board Layout Considerations...................................... 13
Outline Dimensions....................................................................... 15
Ordering Guide .......................................................................... 15
Rev. 0 | Page 2 of 16
ADP3051
SPECIFICATIONS
VIN = 3.6 V @ TA = –40°C to +85°C, unless otherwise noted.
Table 1.
Parameter Conditions Min Typ Max Unit
SUPPLY
Input Voltage Range 2.7 5.5 V
Quiescent Supply Current VFB = 1.0 V 180 300 µA
Shutdown Supply Current
PWM COMPARATOR
Minimum Duty Ratio 0 %
Maximum Duty Ratio 100 %
OSCILLATOR
Oscillator Frequency V
Foldback Frequency V
OUTPUT STAGE
On Resistance, N Channel ISW = 150 mA 150 mΩ
Switch Leakage Current, N Channel VIN = 5.0 V, VSW = 0 V 1 µA
On Resistance, P Channel FB = GND 190 mΩ
Switch Leakage Current, P Channel VSW = 5.0 V 1 µA
Current Limit Threshold 680 1000 1320 mA
ERROR AMPLIFIER
Feedback Input Bias Current 5 nA
Current Sense Gain 2.9 Ω
Transconductance 0.32 mS
Maximum Sink Current 33 µA
Maximum Source Current 33 µA
UNDERVOLTAGE LOCKOUT
Undervoltage Lockout Threshold VIN rising 1.9 2.6 V
Undervoltage Lockout Hysteresis 55 mV
SHDN INPUT THRESHOLD VOLTAGES
Input High Threshold Voltage Referenced to IN −0.5 V
Input Low Threshold Voltage 0.4 V
1
All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC).
1
SHDN = 0 V
≥ 1.5 V, V
COMP
< 0.3 V 200 kHz
OUT
= 0.7 V 410 550 690 kHz
OUT
TA = 25°C 783 800 821 mV Feedback Regulation Voltage
770 830 mV
10 25 µA
Rev. 0 | Page 3 of 16
ADP3051
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
IN, SHDN, COMP, SW, FB to GND
SW to IN –6 V to +0.3 V
PGND to GND –0.3 V to +0.3 V
Operating Ambient Temperature –40°C to +85°C
Operating Junction Temperature –40°C to +125°C
Storage Temperature –65°C to +150°C
θJA, 2-Layer (SEMI standard board) 159°C/W
θJA, 4-Layer (JEDEC standard board) 116°C/W
Lead Temperature Range
Soldering (10 sec) 300°C
Vapor Phase (60 sec) 215°C
Infrared (15 sec) 220°C
–0.3 V to +6 V
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or
loss of functionality.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any
other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability. Absolute maximum ratings apply individually
only, not in combination. Unless otherwise specified, all other
voltages are referenced to GND.
Rev. 0 | Page 4 of 16
ADP3051
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1
NC
2
PGND
3
SW
4
IN
Figure 2. 8-Lead MSOP Pin Configuration
Table 3. Pin Function Descriptions
Pin No. Mnemonic Description
1 NC No Connect. Not internally connected.
2 PGND
Power Ground. Connect PGND to GND at a single point. Use separate power ground and quiet ground planes for
the power and sensitive analog circuitry, respectively. See the Circuit Board Layout Considerations section.
3 SW
Switching Output. SW connects to the drain of the internal power switch and synchronous rectifier. Connect the
output inductor between SW and the load.
4 IN
Power Source Input. IN is the source of the high side P-channel MOSFET switch, and supplies the internal power to
the ADP3051. Bypass IN to GND with a 0.1 µF or greater ceramic capacitor, placed as close as possible to IN.
5 FB
Feedback Voltage Sense Input. FB senses the output voltage. To set the output voltage, connect a resistive voltage divider from the output voltage to FB. The feedback threshold is 0.8 V. See the Setting the Output Voltage
section.
6 COMP
Feedback Loop Compensation Node. COMP is the output of the internal transconductance error amplifier. Place a
series RC network from COMP to GND to compensate the regulator. See the Compensation Design section.
7
SHDN Shutdown Input. Drive SHDN low to turn off the ADP3051; drive SHDN to within 0.5 V of VIN to turn on the
ADP3051. See the Shutdown section.
8 GND Ground.
ADP3051
TOP VIEW
(Not to Scale)
8
7
6
5
GND
SHDN
COMP
FB
04768-0-021
Rev. 0 | Page 5 of 16
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