REV. A

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a

ADP3158/ADP3178

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

Tel: 781/329-4700

www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2001

4-Bit Programmable

Synchronous Buck Controllers

FUNCTIONAL BLOCK DIAGRAM

CMP

+

–

DRVH

LRDRV2

LRFB2

LRFB1

LRDRV1

COMP

DRVL

GND

CS–

CS+

PWM

DRIVE

VCC

CT

OSCILLATOR

UVLO

& BIAS

REFERENCE

REF

REF

VID DAC

DAC+20%

ADP3158/ ADP3178

VID3

VID2

VID1

VID0

FEATURES

Optimally Compensated Active Voltage Positioning

with Gain and Offset Adjustment (ADOPT™) for

Superior Load Transient Response

Complies with VRM Specifications with Lowest

System Cost

4-Bit Digitally Programmable 1.3 V to 2.05 V Output

N-Channel Synchronous Buck Driver

Total Accuracy

0.8% Over Temperature

Two On-Board Linear Regulator Controllers Designed

to Meet System Power Sequencing Requirements

High Efficiency Current-Mode Operation

Short Circuit Protection for Switching Regulator

Overvoltage Protection Crowbar Protects Micro-

processors with No Additional External Components

APPLICATIONS

Core Supply Voltage Generation for:

Intel Celeron™

GENERAL DESCRIPTION

The ADP3158 and ADP3178 are highly efficient synchronous

buck switching regulator controllers optimized for converting a

5 V main supply into the core supply voltage required by high-

performance processors. These devices use an internal 4-bit DAC

to read a voltage identification (VID) code directly from the

processor, which is used to set the output voltage between 1.3 V

and 2.05 V. They use a current mode, constant off-time archi-

tecture to drive two N-channel MOSFETs at a programmable

switching frequency that can be optimized for regulator size and

efficiency.

The ADP3158 and ADP3178 also use a unique supplemental

regulation technique called Analog Devices Optimal Positioning

Technology (ADOPT) to enhance load transient performance.

Active voltage positioning results in a dc/dc converter that

meets the stringent output voltage specifications for high-

performance processors, with 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 it

is always optimally positioned for a system transient. They also

provide accurate and reliable short circuit protection and

adjustable current limiting. The devices include an integrated

overvoltage crowbar function to protect the microprocessor

from destruction in case the core supply exceeds the nominal

programmed voltage by more than 20%.

The ADP3158 and ADP3178 contain two linear regulator

controllers that are designed to drive external N-channel

MOSFETs. The outputs are internally fixed at 2.5 V and 1.8 V

in the ADP3158, while the ADP3178 provides adjustable out-

puts that are set using an external resistor divider. These

linear regulators are used to generate the auxiliary voltages

(AGP, GTL, etc.) required in most motherboard designs,

and have been designed to provide a high bandwidth load-

transient response.

The ADP3158 and ADP3178 are specified over the commercial

temperature range of 0

°C to 70°C and are available in a 16-lead

SOIC package.

ADOPT is a trademark of Analog Devices, Inc.

Pentium is a registered trademark of Intel Corporation.

Celeron is a trademark of Intel Corporation.