ADP3156JR-1.5 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

ADP3156JR-1.5

Dual Power Supply Controller for Desktop Systems

Analog Devices 

a

Dual Power Supply Controller

for Desktop Systems

ADP3156

FEATURES

Active Voltage Positioning with Gain and Offset

Adjustment

Optimal Compensation for Superior Load Transient

Response

Fixed 1.5 V, 1.8 V and 2.5 V Output Versions

Dual N-Channel Synchronous Driver

On-Board Linear Regulator Controller

Total Output Accuracy ؎1% Over Temperature

High Efficiency, Current-Mode Operation

Short Circuit Protection

Overvoltage Protection Crowbar Protects Loads with

No Additional External Components

Power Good Output

SO-16 Package

APPLICATIONS

Desktop Computer Supplies

ACPI-Compliant Power Systems

General Purpose DC-DC Converters

GENERAL DESCRIPTION

The ADP3156 is a highly efficient synchronous buck switching

regulator controller optimized for converting the 3.3 V or 5 V

main supply into lower supply voltages required on the mother-

boards of Pentium® III and other high performance processor

systems. The ADP3156 uses a current mode, constant off-time

architecture to drive two external N-channel MOSFETs at a

programmable switching frequency that can be optimized for

size and efficiency. It also uses a unique supplemental regulation

technique called active voltage positioning to enhance load

transient performance. Active voltage positioning results in a

DC/DC converter that provides the best possible transient re-

sponse using the minimum number of output capacitors and

smallest footprint. Unlike voltage-mode and standard current-

mode architectures, active voltage positioning adjusts the output

voltage as a function of the load current so that it is always

optimally positioned for a system transient.

The ADP3156 provides accurate and reliable short circuit

protection and adjustable current limiting. It also includes an

integrated overvoltage crowbar function to protect the micro-

processor from destruction in case the core supply exceeds the

nominal programmed voltage by more than 15%.

FUNCTIONAL BLOCK DIAGRAM

VCC DRIVE1 DRIVE2 PGND AGND PWRGD SENSE+ SENSE–

DELAY

NONOVERLAP

SD

DRIVE

VREF +15%

2R

CROWBAR

IN OFF

CMPI

VREF +5% VREF –5%

S

Q

R

VT2

VT1

VREF

R

gm

REFERENCE

CT

CMPT

OFF-TIME VIN

CONTROL SENSE–

1.20V

ADP3156

VLDO

FB

CMP

The ADP3156 contains a linear regulator controller that is

designed to drive an external N-channel MOSFET. This linear

regulator is used to generate the auxiliary voltages (AGP, GTL,

etc.) required in most motherboard designs, and has been de-

signed to provide a high bandwidth load-transient response. A

pair of external feedback resistors sets the linear regulator out-

put voltage.

VO2

1000␮F

VCC +12V

22␮F 1␮F

R1

35k⍀

20k⍀

R2

SD VCC

DRIVE1

VLDO

ADP3156

CCOMP

200pF

SENSE+

FB

CMP SENSE–

DRIVE2

CT

AGND PGND

VIN +5V

CIN

+

L RSENSE

VO

+

1nF

CO

Figure 1. Typical Application

Pentium is a registered trademark of Intel Corporation.

All other trademarks are the property of their respective holders.

REV. 0

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700 World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 1999

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