REV. A

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a

ADP3421

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., 2002

Geyserville-Enabled DC-DC

Converter Controller for Mobile CPUs

FEATURES

Lowest Processor Dissipation for Longest Battery Life

Best Transient Containment

Minimum Number of Output Capacitors

System Power Management Compliant

Fast, Smooth Output Transition During VID Code

Change

Programmable Current Limit

Power Good

Integrated LDO Controllers for Clock and I/O Supplies

Programmable UVLO

Soft Start with Restart Lock-In

APPLICATIONS

Geyserville-Enabled Core DC-DC Converters

Fixed Voltage Mobile CPU Core DC-DC Converters

Notebook/Laptop Power Supplies

Programmable Output Power Supplies

GENERAL DESCRIPTION

The ADP3421 is a hysteretic dc-dc buck converter controller

with two auxiliary linear regulator controllers. The ADP3421

provides a total power conversion control solution for a micro-

processor by delivering the core, I/O, and clock voltages. The

optimized low-voltage design is powered from the 3.3 V system

supply and draws only 10

µA maximum in shutdown. The main

output voltage is set by a 5-bit VID code. To accommodate the

transition time required by the newest processors for on-the-

fly VID changes, the ADP3421 features high-speed operation

to allow a minimized inductor size that results in the fastest change

of current to the output. To further allow for the minimum

number of output capacitors to be used, the ADP3421 features

active voltage positioning that can be optimally compensated

to ensure a superior load transient response. The main output

signal interfaces with the ADP3410 dual MOSFET driver,

which is optimized for high speed and high efficiency for driving

both the upper and lower (synchronous) MOSFETs of the

buck converter.

FUNCTIONAL BLOCK DIAGRAM

VHYS

VID3

VID4

LTB

LTI

LTO

CLSET

VID2

VID1

VID0

CLKDRV

CLKFB

IODRV

IOFB

CS–

GND

OUT

VCC

RAMP

REG

CS+

DACOUT

CORE

SSC

SSL

UVLO

PWRGD

SD

LEVEL

TRANSLATOR

EN

CORE

COMPARATOR

CORE CONTROLLER

ADP3421

CLOCK LDO

CONTROLLER

I/O LDO

CONTROLLER

VIN/VCC

MONITOR AND

UVLO BIAS

REFERENCE

CONTROLLER

BIAS AND

REFERENCE

SOFT START

TIMER

AND

POWER GOOD

GENERATOR

BIAS EN

VID DAC

CURRENT

LIMIT

COMPARATOR