LOW COST PWM CONTROLLER
January 13, 2000
AN99-5
APPLICATION NOTE FOR SC1101/03
INTRODUCTION
DESCRIPTION
The SC1101/03 is a versatile, low-cost,
voltage-mode PWM controller designed for
use in single ended DC/DC power supply ap-
plications. A simple, fixed-voltage buck regu-
lator can be implemented using the
SC1101/03 with a minimum of external com-
ponents. Internal level shift and drive circuitry
eliminates the need for an expensive p-
channel, high-side switch. The small device
footprint allows for compact circuit design.
SC1101/03 features include a temperature
compensated voltage reference, triangle
wave oscillator, current limit comparator, fre-
quency shift over-current protection, and an
internally compensated error amplifier. Pulse
by pulse current limiting is implemented by
sensing the differential voltage across an ex-
ternal resistor, or an appropriately sized PC
board trace.
The SC1101/03 operates at a fixed frequency
of 200kHz, providing an optimum compro-
mise between efficiency, external component
size, and cost.
The SC1103鈥檚 manufacturing process has
been optimized for 12V operation and is
capable of handling up to 26V at it鈥檚 BST
pin.
APPLICATIONS
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Pentium廬 P55 Core Supply
Low Cost Microprocessor Supplies
Peripheral Card Supplies
Industrial Power Supplies
High Density DC/DC Conversion
FEATURES
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Low cost / small size
Switch mode efficiency (90%)
1% reference voltage accuracy
Over current protection
500mA output drive
5V to 12V Input power source
BLOCK DIAGRAM
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漏 2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
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