Synchronous Current-Mode with

Constant On-time, PWM Buck

Preliminary Technical Data

ADP1872

Rev. PrA

PR08297-0-6/09(PrA)

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

responsibilityis assumedbyAnalogDevicesforitsuse,norforanyinfringementsof patentsorother

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

©200

9 Analog Devices, Inc. All rights reserved.

FEATURES

Power input voltage range: 2.7V to 20V

Bias supply voltage range: 2.7V to 5.5V

Minimum Output voltage 0.6V

1.0% Accuracy, 0.6V Reference Voltage

Supports all N-channel MOSFET power Stage

Available in 300 KHz, 600 KHz and 1.0 MHz

No Current Sense Resistor Required

Power saving mode under light loads

Resistor Programmable Current Sense Gain

Thermal overload protection

Short circuit protection

Precision Enable Input

Integrated boot strap diode for High Side Drive

180

μA typical shutdown supply current

Starts into a pre-charged load

Small, 10-lead MSOP package

APPLICATIONS

Telecom and networking systems

Mid to High End servers

Set-top boxes

Medical imaging systems

DSP core power supplies

GENERAL DESCRIPTION

The ADP1872 is a versatile current mode synchronous step-

down controller. ADP1872 uses a constant ON-time, pseudo

fixed frequency with programmable Current Sense Gain

Current Control scheme for superior transient response,

optimal stability and current limit protection. It utilizes Valley

Current Mode Control architecture for optimum performance

at low Duty Cycles. It drives an all N-channel power stage to

regulate output voltages as low as 0.6V.

ADP1872 is well suited for a wide range of applications, from

Set Top Box design to Communication Infrastructure. The IC

can operate from a 2.7V to 5.5V supply but the power input can

be as high as 20V.

ADP1872 is available in three versions ADP1872A, ADP1872B

and ADP1872C with each version programmed respectively to

300KHz, 600KHz and 1MHz pseudo fixed frequency.

ADP1872 includes an internally fixed, soft start period to limit

input in-rush current from the input supply during startup and

output. The low-side current sense, current-gain scheme and

PSM / Forced PWM options reduces external part count and

improves efficiency.

The ADP1872 operates over the –40°C to +125°C junction

temperature range and is available in a 10-pin MSOP package.