PWM, Step-Down DC-to-DC Controller

with Margining and Tracking

ADP1822

Rev. B

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibilityis assumedbyAnalogDevicesforitsuse,norforanyinfringements of patents or other

rightsofthirdpartiesthatmayresultfromitsuse.Specificationssubjecttochangewithoutnotice.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

©2006 Analog Devices, Inc. All rights reserved.

FEATURES

Wide input voltage range: 1 V to 24 V

Wide output voltage range: 0.6 V to 85% of input voltage

1% accuracy, 0.6 V reference voltage

Output voltage margining control

Output voltage tracking

All N-channel MOSFET

300 kHz, 600 kHz, or up to 1.2 MHz synchronized frequency

No current sense resistor required

Power-good output

Programmable soft start with reverse current protection

Current-limit protection

Thermal overload protection

Overvoltage protection

Undervoltage lockout

1 μA shutdown supply current

Small, 24-lead QSOP package

APPLICATIONS

Telecom and networking systems

High performance servers

Medical imaging systems

DSP core power supplies

Microprocessor core power supplies

Mobile communication base stations

Distributed power

GENERAL DESCRIPTION

The ADP1822 is a versatile and inexpensive synchronous voltage-

mode PWM step-down controller. It drives an all N-channel power

stage to regulate an output voltage as low as 0.6 V.

The ADP1822 regulated output can track another power supply

and be dynamically adjusted up or down with the controller’s

margining-control inputs, making it ideal for high reliability

applications. It is well suited for a wide range of high power

applications, such as DSP power and processor core power in

telecom, medical imaging, high performance servers, and

industrial applications. It operates from a 3.0 V to 5.5 V supply

with power input voltage ranging from 1.0 V to 24 V.

The ADP1822 can operate at any frequency between 300 kHz

and 1.2 MHz either by synchronizing with an external source or

an internally generated, logic-controlled clock of 300 kHz or

600 kHz. It includes an adjustable soft start to allow sequencing

and quick power-up while preventing input inrush current.

Output reverse-current protection at startup prevents excessive

output voltage excursions. The adjustable, virtually lossless

current-limit scheme reduces external part count and improves

efficiency.

The ADP1822 operates over the −40°C to +85°C temperature

range and is available in a 24-lead QSOP package.

BIAS INPUT

5V

1µF

10Ω

FREQ

SYNC

MAR

MSEL

COMP

SS

100nF

IRF3711

IRF3711

1µH

180µF

20V

1000µF

4V

DH

BST

SW

DL

PGND

TRKP

TRKN

FB

MDN

MUP

0.1µF

VCC

ADP1822

6.18kΩ

POWER INPUT

2.25V TO 24V

OUTPUT

1.8V, 15A

1µF

80.6kΩ

309pF

AGND DGND

TRACKING

SIGNAL INPUT

2.2pF

1nF

15pF

158kΩ

316kΩ

CMOSH-3

20kΩ

10kΩ

VCC

PWGD

CSL

SHDN

Figure 1. Typical Operating Circuit

97

87

0

16

LOAD CURRENT (A)

96

95

94

93

92

91

90

89

88

2

4

6

8

10

12

14

1.8V OUTPUT

3.3V OUTPUT

Figure 2. Efficiency vs. Load Current, 5 V Input