Buck or Buck-Boost(Inverting)
Current Mode Controller
POWER MANAGEMENT
Description
The SC4508 is a low voltage current mode switching regu-
lator controller that drives a P-channel power MOSFET
with programmable switching frequency. It can be con-
figured in either buck or buck boost (inverting) convert-
ers. The converters can be operated from 2.7V to 15V
input voltage range. The typical operating supply current
is 3mA and a shutdown pin allows the user to turn the
controller off reducing it to less than 200
µ
A. The output
voltage can adjusted by external resistor divider. The
switching frequency is programmable up to 1.5MHz,
allowing small inductor and capacitor values to minimize
PCB space. The operating current level is programmable
via an external sense resistor. Accessible reference volt-
age allows users to make output voltage as low as they
want.
SC4508
Features
Wide input voltage range 2.7V to 15V
Programmable output voltage
Programmable switching frequency up to 1.5MHz
Buck or buck boost(inverting) configuration
Current mode control with slope compensation
Very low quiescent current in shutdown mode
Accessible reference voltage
MLPQ-12 package
Applications
Low power point of use converters
Single or multiple output low power converters
Positive and/or negative output voltage
DSL cards
Graphic cards
I/O cards
Negative bias supplies
Typical Application Circuits
Vin
Vin
VDD
VDD
VREF
VREF
FB+
FB-
COMP
CS
FB+
OUT
FB-
SC4508
SC4508
CS
COMP
SS/SHDN
GND
OSC
SS/SHDN
GND
OSC
OUT
Revision: November 30, 2004
1
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