US3027
5 BIT PROGRAMMABLE SYNCHRONOUS BUCK
PLUS TRIPPLE LDO CONTROLLER
PRELIMINARY DATASHEET
FEATURES
Designed to meet VRM 9.0 specification for
next generation micrprocessors
On board 5 bit DAC programs the output
voltage from 1.075V to 1.850V in 25mV steps
Linear regulator controller on board for 1.8V
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 1.5V
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 US3027 controller IC is specifically designed to meet
VRM 9.0 specification for next generation microproces-
sor applications requiring multiple on board regulators .
The US3027 provides a single chip controller IC for
the Vcore , 3LDO controllers, one with the auto-
matic select pin that connects to the TYPE DETECT
pin of the AGP slot for the AGP Vddq supply, one
for GTL+ and the other for the 1.8V chip set regula-
tor as required for the next generation PC applica-
tions. The US3027 is designed to use either Bipolar
transistors for Vout3(1.5V) and Vout4(1.8V) or if Vaux
pin is connected to 12V, then MOSFETs can also be
used as external pass elements. No external resis-
tor divider is necessary for any of the regulators.
The switching regulator feature a patented topology that
in combination with a few external components as shown
in the typical application circuit ,will provide well in ex-
cess 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 US3027 also fea-
tures,
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 condition 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 outputs is out-
side of a pre programmed window.
APPLICATIONS
Total Power Soloution for Next Generation Intel
Processor application
AMD K7 Low Cost Solution
TYPICAL APPLICATION
5V
3.3V
LINEAR
CONTROL
SWITCHER
CONTROL
Vout1
Vout2
US3027
LINEAR
CONTROL
Vout3
LINEAR
CONTROL
Vout4
3027app3-1.0
PACKAGE ORDER INFORMATION
Ta (°C)
0 TO 70
Rev. 1.3
12/8/00
Device
US3027CW
Package
28 pin Plastic SOIC WB
4-1
UNISEM [ UNISEM ]
