US3033
PWM SWITCHER & LINEAR
CONTROLLER IC
FEATURES
LDO Controller allows the use of a low cost
pass transistor for the I/O supply
8 pin SOIC combines switching and linear
controller
Internal Pre-regulator Eliminates Cross talk
between Switching & Linear regulators
Automatic shut down of the linear regulator
when connected to the Vcc2 Det pin
On board MOSFET driver
Fastest transient response of any controller
method. ( 0 to 100% Duty Cycle in 100 nS )
1% internal voltage reference
Internal Under Voltage Lockout protects
MOSFET during start-up
DESCRIPTION
The US3033 IC
combines a switching controller and
a linear regulator controller all in a compact 8 pin
surface mount package,
providing a
total solution
for
dual supply processor applications such as an
Intel
P55C
™,
AMD K6™, as well as Cyrix 6X86L™ and
the M2™processors.
Typically in these applications a
dual supply regulator converts 5V to 3.3V for I/O supply
and a jumper programmable supply of 1.25V to 3.5V for
CORE supply .The linear regulator controller portion in
the US3033 is a programmable controller allowing flex-
ibility for the I/O regulator and has a minimum of 50mA
drive current capability designed to provide ample cur-
rent for an external pass transistor. The IC uses an inter-
nal regulator generated from the 12V supply to power
the controller as well as the 12V supply to drive the power
MOSFET, allowing a low cost N channel MOSFET
switch to be used. The IC also includes an error com-
parator for fast transient response, a precise voltage ref-
erence for setting the output voltage as well as a direct
drive of the MOSFET for the minimum part count.
APPLICATIONS
Dual supply low voltage processor applications,
such as: P55C™,CYRIX M2™, POWER PC™ and
AMD K6™
Simple 5V to 3.3V switcher for Pentium with AGP
or Pentium II™ applications
TYPICAL APPLICATION
5V
C1
R9
Q1
R10
R6
C6
I/O
D2
C8
R7
5V
R8
12V
8 7 6 5
V12 Drv2 Vfb2 Gnd
CPU
Vcc2 Det
US3033
Drv1V12swVfb1 Vhyst
1 2 3 4
C3
L1
Q2
C2
D1
R3
C5
L2
Core
R4
C7
R5
3033app1-1.1
Typical application of US3033 in a flexible mother board designed for Intel P55™,P54™
AMD K5,K6™ as well as Cyrix M1™ and M2™ applications.
Notes: P54C,P55C,Pentium II are trade marks of Intel Corp. K5 & K6 are trade marks of AMD corp. Cyrix 6X86L,M1,M2 are trade marks
of Cyrix Corp. Power PC is trade mark of IBM Corp.
PACKAGE ORDER INFORMATION
TA (°C)
0 TO 70
Rev. 1.5
1/14/99
8 PIN PLASTIC
SOIC (S)
US3033CS
4-1
UNISEM [ UNISEM ]
