ADP3161

a

REV. 0

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© Analog Devices, Inc., 2001

4-Bit Programmable 2-Phase

Synchronous Buck Controller

FEATURES

ADOPT™ Optimal Positioning Technology for Superior

Load Transient Response and Fewest Output

Capacitors

Active Current Balancing Between Both Output Phases

VRM 8.4-Compatible Digitally Programmable 1.3 V to

2.05 V Output

Dual Logic-Level PWM Outputs for Interface to External

High-Power Drivers

Total Output Accuracy

0.8% Over Temperature

Current-Mode Operation

Short Circuit Protection

Power-Good Output

Overvoltage Protection Crowbar Protects

Microprocessors with No Additional

External Components

APPLICATIONS

Desktop PC Power Supplies for:

VRM Modules

GENERAL DESCRIPTION

The ADP3161 is a highly efficient dual output synchronous buck

switching regulator controller optimized for converting a 5 V or

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

performance processors such as Pentium

uses 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. The ADP3161 uses a current

mode PWM architecture to drive two logic-level outputs at a

programmable switching frequency that can be optimized for

VRM size and efficiency. The output signals are 180 degrees out of

phase, allowing for the construction of two complementary buck

switching stages. These two stages share the dc output current

to reduce overall output voltage ripple. An active current bal-

ancing function ensures that both phases carry equal portions

of the total load current, even under large transient loads, to

minimize the size of the inductors.

FUNCTIONAL BLOCK DIAGRAM

2-PHASE

DRIVER

LOGIC

UVLO

& BIAS

3.0V

REFERENCE

OSCILLATOR

SET

RESET

CROWBAR

VCC

REF

GND

CT

COMP

PWM1

PWM2

PWRGD

CS–

CS+

FB

VID

DAC

VID3

VID2

VID1

VID0

CMP

CMP

DAC–18%

DAC+24%

ADP3161

CMP3

CMP2

CMP1

The ADP3161 also uses a unique supplemental regulation tech-

nique called active voltage positioning to enhance load transient

performance. Active voltage positioning results in a dc/dc con-

verter 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

that it is always optimally positioned for a system transient. The

ADP3161 also provides accurate and reliable short circuit protec-

tion and adjustable current limiting.

The ADP3161 is specified over the commercial temperature

range of 0

°C to 70°C and is available in a 16-lead narrow body

SOIC package.

ADOPT is a trademark of Analog Devices Inc.

Pentium is a registered trademark of Intel Corporation