POWER MANAGEMENT

1

www.semtech.com

SC1101

Asynchronous Voltage

Mode PWM Controller

Features

Applications

Revision: May 25, 2005

Typical Application Circuit

Description

Low cost / small size

Switch mode efficiency up to 95%

1% reference voltage accuracy

Over current protection

500mA output drive

SO-8 package

Pentium® P55 Core Supply

Low Cost Microprocessor Supplies

Peripheral Card Supplies

Industrial Power Supplies

High Density DC/DC Conversion

The SC1101 is a versatile, low-cost, voltage-mode PWM

controller designed for low output voltage DC/DC power

supply applications. A simple, fixed-voltage buck

regulator can be implemented using the SC1101 with a

minimum of external components. 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 features include a temperature compensated

voltage reference, triangle wave oscillator, current limit

comparator, frequency shift over-current protection, and

an internally compensated error amplifier. Pulse by pulse

current limiting is implemented by sensing the

differential voltage across an external resistor, or an

appropriately sized PC board trace.

The SC1101 operates at a fixed frequency of 200kHz,

providing an optimum compromise between efficiency,

external component size, and cost.

Q1

IRLR3103

R4

2.2

R2

1k

D2

MBRD1035L

R1

10

L1

4uH

C8

330/2.5V

C9

330/2.5V

C10

330/2.5V

C3

150/6.3V

C2

150/6.3V

C5

0.001

R7

127

R6

76.8 *see note

C1

1.0

C6

0.01

+

+5V

GND

C7

0.1

C11

1.0

R5

0.05

R3

1k

GND

VCC

1

CS(-)

2

CS(+)

3

PGND

4

DH

5

BST

6

FB

7

GND

8

U1

SC1101

* NOTE:

R6 = R7 x (Vout/1.25 - 1) rounded to nearest 1%value

C4

0.1

Vout = 2V @ 10A

+12V