US3021B

4-1

Rev. 1.4

12/8/00

TYPICAL APPLICATION

TYPICAL APPLICATION

DESCRIPTION

DESCRIPTION

The US3021B controller IC is specifically designed to

meet Intel specification for next generation micropro-

cessor applications requiring multiple on board regula-

tors . The US3021B provides a single chip control-

ler IC for the Vcore , 3LDO controllers, one with the

automatic select pin that connects to the TYPE DE-

TECT pin of the AGP slot for the AGP Vddq supply,

one for GTL+ and the other for the 1.8V chip set

regulator as required for the next generation PC

applications. The US3021B typically uses Bipolar

transistors for Vout3(1.5V) and Vout4(1.8V) however

if Vaux pin is connected to 12V, then MOSFETs can

also be used as external pass elements. No exter-

nal resistor divider is necessary for any of the regu-

lators. The switching regulator feature a patented topol-

ogy that in combination with a few external components

as shown in the typical application circuit ,will provide

well in excess of 20A of output current for an on- board

DC/DC converter while automatically providing the right

output voltage via the 5 bit internal DAC .The US3021B

also features, loss less current sensing for both

switcher by using the Rds-on of the high side Power

MOSFET as the sensing resistor, an output under

voltage shutdown that detects short circuit condi-

tion for the linear outputs and latches the system

off, and a Power Good window comparator that switches

its open collector output low when any one of the out-

puts is outside of a pre programmed window.

Provides Single Chip Solution for Vcore,

GTL+ ,AGP Bus, and 1.8V

Automatic Voltage Selection for AGP slot

Vddq supply

Linear regulator controller on board for 1.8V

Designed to meet Intel Latest VRM specifica-

tion for next generation micrprocessors

On board DAC programs the output voltage

from 1.3V to 3.5V

Linear regulator controller on board for 1.5V

GTL+ supply

Loss less Short Circuit Protection for all

outputs

Synchronous operation allows maximum

efficiency

Patented architecture allows fixed frequency

operation as well as 100% duty cycle during

dynamic load

Minimum part count

Soft Start

High current totem pole driver for direct

driving of the external Power MOSFET

Power Good function Monitors all Outputs

OVP Circuitry Protects the Switcher Output

and generates a Fault output

PACKAGE ORDER INFORMATION

PACKAGE ORDER INFORMATION

PRELIMINARY DATASHEET

FEATURES

FEATURES

5 BIT PROGRAMMABLE SYNCHRONOUS BUCK

PLUS TRIPPLE LDO CONTROLLER

APPLICATIONS

APPLICATIONS

Total Power Soloution for Next Generation Intel

Processor application

Ta (

°C)

Device

Package

0 TO 70

US3021BCW

28 pin Plastic SOIC WB

3021Bapp3-1.1

LINEAR

CONTROL

LINEAR

CONTROL

SWITCHER

CONTROL

US3021B

Vout3

5V

Vout1

Vout4

LINEAR

CONTROL

Vout2

3.3V