POWER MANAGEMENT

1

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SC1104A/B

Simple, Synchronous

Voltage Mode PWM Controller

PRELIMINARY

.eatures

Applications

Revision 3, October 2001

Typical Application Circuit

Description

The SC1104A/B is a versatile voltage-mode PWM con-

troller designed for use in single ended DC/DC power

supply applications. A simple, fixed frequency high effi-

ciency buck regulator can be implemented using the

SC1104A/B 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.

SC1104A/B features include temperature compensated

voltage reference, triangle wave oscillator, current limit

comparator and an externally compensated error

amplifier. Current limit is implemented by sensing the

voltage drop across the top .ET’s R

The SC1104A/B operates at a fixed frequency of 300/

600 kHz, providing an optimum compromise between

efficiency, external component size, and cost. 600kHz

switching frequency is typically reserved for the 5V

operation only.

SC1104A/B has a thermal protection circuit, which is

activated if the junction temperature exceeds 150°C.

Typical Distributed Power Supply

Q1

Si4884DY

Q2

Si4874DY

L1

1.5-3uH

C9

0.1

C10

220/4V

C11

220/4V

C12

220/4V

C13

220/4V

C6

47/16V

C5

47/16V

+

_

+

_

Vin 5 to 12V

3.3V

R3

1.00k

R4

2.32k

C3

0.1

C14-17

1.0

C7

47/16V

VCC

7

DL

3

DH

4

PHASE

6

COMP/SS

1

BST

5

SENSE

8

GND

2

U1

SC1104A/B

R6

1-5.1

R7

1-5.1

R1

2k

D1

MBRA130L

R2

10

C2

0.01

C4

10.0

C1

220-680pF

C8

0.1-0.22

R5

200-1k

R8

10

D2

(opt)

.igure 1