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www.fairchildsemi.com
Features
Current Sensing is achieved using MOSFET R
DS(ON)
Programmable output from 1.3V to 3.5V using an
integrated 5-bit DAC
85% efficiency typical at full load
Adjustable operation from 100KHz to 1MHz
Integrated Power Good and Enable/Soft Start functions
Overvoltage protection pin controls external SCR
Short circuit protection with current limiting
Drives N-channel MOSFETs
24 pin SSOP and SOIC package
Meets Intel Pentium II specifications using minimum
number of external components
On board Linear regulator for GTL termination
On board fixed linear regulator for Clock power supply
TTL Compatible inputs
Applications
Power supply for Pentium
II
VRM for Pentium II processor
Programmable step-down power supply
Block Diagram
Description
The RC5055 is a triple combo combining a synchronous
DC-DC controller with a fixed 2.5V output linear regulator
and an adjustable linear regulator. The synchronous mode
DC-DC controller provides an accurate, programmable
output voltage for all Pentium II CPU applications. It uses a
5-bit D/A converter to program the output voltage from 1.3V
to 3.5V and uses a high level of integration to deliver load
currents in excess of 17A from a 5V source with minimal
external circuitry. Synchronous-mode operation offers opti-
mum efficiency over the entire specified output voltage
range, and the internal oscillator can be programmed from
100KHz to 1MHz for additional flexibility in choosing exter-
nal components. An on-board precision low TC reference
achieves tight tolerance voltage regulation without expensive
external components. The RC5055 also offers integrated
functions including Power Good, Output Enable/Soft Start,
over-voltage protection and current limiting.
D/A
CONVERTER
(DAC)
OSCILLA
FIXED 2.5V
LINEAR
REGULATOR
TOR
SOFT-
REFERENCE
POWER-ON
115%
110%
90%
INHIBIT
COPWM
EAMP
VCC
PGOOD
16
23
20
3
19
18
17
21
22
15
11
12
1
2
6
7
8
9
10
14
13
24
4
5
SS
OVP
PWM
GNDA
LVIN
OPAMP1
LVOUT
VSEN
OCSET
VID0
FB
COMP
RT
GATE1
FB1
DACOUT
VREF
VOVER-
+
-
COVER-
CLOGIC
BOOT
UGATE
PHASE
LGATE
PGND
200
μ
A
10
μ
A
4V
+
-
+
-
+
-
+
-
+
-
+
-
RC5055
Programmable S ync hronous DC-DC Converter
Controller for Low Voltage Mic roproc essors,
V tt and Cloc k Linear Regulator
Pentium is a registered trademark of Intel Corporation.
Rev. 1.01