POWER MANAGEMENT

1

www.semtech.com

SC1104A/B

Simple, Synchronous

Voltage Mode PWM Controller

Features

Applications

Revision: November 22, 2006

Typical Application Circuit

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 ampli-

fier. Current limit is implemented by sensing the voltage

drop across the top FET’s R

The SC1104 operates at fixed frequencies of

300kHz(A) or 600kHz(B) providing an optimum com-

promise between efficiency, external component size,

and cost. 600kHz switching frequency is reserved for

the SC1104B, +5V

SC1104A/B has a thermal protection circuit, which is

activated if the junction temperature exceeds 150°C.

Up to +14V input, 300kHz operation (SC1104A)

Up to +7V input, 600kHz operation (SC1104B)

High efficiency (>90%)

1% Reference voltage accuracy

Hiccup mode over current protection

Robust output drive

R

Industrial temperature range

8-Lead SOIC package. Pb-free package available,

fully WEEE and RoHS compliant

Termination supplies

Low cost microprocessor supplies

Peripheral card supplies

Industrial power supplies

High density DC/DC conversion

Typical Distributed Power Supply

Figure 1

Q1

Si4884DY

Q2

Si4874DY

L1

1.5-6.8uH

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

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

200-2k

D1

MBRA130L

C2

0.01

C4

10.0

C1

510-1500pF

C8

0.1-0.33

R5

200-1k

R8

opt

D2

(opt)

Description