POWER MANAGEMENT

1

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SC1103

Asynchronous Voltage Mode PWM

Controller for 12V Input

Features

Applications

Revision: July 28, 2005

Typical Application Circuit

Description

The SC1103 is a versatile, low-cost, voltage-mode PWM

controller designed for 12V input DC/DC power supply

applications. A simple, fixed-voltage buck regulator can

be implemented using the SC1103 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.

SC1103 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 SC1103 operates at a fixed frequency of 200kHz,

providing an optimum compromise between efficiency,

external component size, and cost.

Low cost / small size

Switch mode efficiency up to 95%

1% reference voltage accuracy

Over current protection

500mA output drive

5V to 12V Input power source

Lead free package available. Fully WEEE and RoHS

compliant

Pentium® P55 Core Supply

Low Cost Microprocessor Supplies

Peripheral Card Supplies

Industrial Power Supplies

High Density DC/DC Conversion

12V to 3.3V @ 10A with “flying capacitor” boost voltage.

Q1

IRLR3103

R4

2.2

R2

1k

D2

MBRD1035L

R1

10

L1

6uH

C8

220/4V

C9

220/4V

C10

220/4V

C3

47/16V

C2

47/16V

C5

0.001

R7

127

R6

127*see note

C1

1.0

C6

0.01

+

+12V

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

SC1103

* NOTE:

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

C4

0.1

Vout = 2.5V @ 10A

+20V