US3021B
5 BIT PROGRAMMABLE SYNCHRONOUS BUCK
PLUS TRIPPLE LDO CONTROLLER
PRELIMINARY DATASHEET
FEATURES
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
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.
APPLICATIONS
Total Power Soloution for Next Generation Intel
Processor application
TYPICAL APPLICATION
5V
3.3V
LINEAR
CONTROL
SWITCHER
CONTROL
Vout1
Vout2
US3021B
LINEAR
CONTROL
Vout3
LINEAR
CONTROL
Vout4
3021Bapp3-1.1
PACKAGE ORDER INFORMATION
Ta (°C)
0 TO 70
Rev. 1.4
12/8/00
Device
US3021BCW
Package
28 pin Plastic SOIC WB
4-1
UNISEM [ UNISEM ]
