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P
PRELIMINARY INFORMATION
describes products that are not in full production at the time of printing. Specifications are based on design goals
and limited characterization. They may change without notice. Contact Fairchild Semiconductor for current information.
www.fairchildsemi.com
Features
High power switched-mode DC-DC controller can source
in excess of 13A
Output voltage adjustable from 1.5V to 3.6V
85% efficiency
Cumulative accuracy < 3% over line, load, temperature
and transient variations
Overvoltage and short circuit protection
Built-in soft start
Applications
Precision 2.xV CPU core regulator for Intel Pentium
MMX processors
Precision 2.xV or 3.xV CPU core regulator for
AMD-K6 MMX and Cyrix 6x86MX (M2)
processors
Description
The RC5031 is a high power, switch-mode DC-DC control-
ler that provides an accurate, adjustable output for high-end
microprocessors requiring unique supply voltages. The
RC5031 has built-in Soft Start feature which offers system
protection during power-up by reducing both inrush current
and output overshoot. When combined with the appropriate
external circuitry, the RC5031 can deliver load currents as
high as 13A at efficiencies as high as 88%. Through the use
of external resistors, the RC5031 can generate output volt-
ages from 1.5V up to 3.6V.
The RC5031 is designed to operate in a “constant on-time”
(patent pending) control mode under all load conditions. Its
accurate low TC reference eliminates the need for precision
external components in order to achieve the tight tolerance
voltage regulation required by most CPU-based applications.
Short circuit current protection is provided through the use
of a current sense resistor, while overvoltage protection is
provided internally.
The RC5031 is a highly efficient switched-mode DC-DC
converter that can select a 3.5V or user-adjustable output.
With the appropriate external components, the RC5031 can
be configured to implement a switchable power supply
system for Pentium and K6 processors.
Block Diagram
RC5031
FEEDBACK
CONTROL
OSCILLATOR
DIGITAL
LOGIC
SWITCHING REGULATOR
1.5V
REFERENCE
SUPPLY VOLTAGE
FOR CPU CORE
VREF
65-5031-01
+12V
+5V
RC5031
Adjustable S witc hing Regulator
Rev. 0.9.3
Pentium is a registered trademark of Intel Corporation.
MMX is a trademark of Intel Corporation.
K6 is a trademark of AMD Corporation.
6x86MX is a trademark of Cyrix Corporation.