SC1103

© 2000 SEMTECH CORP.

652 MITCHELL ROAD NEWBURY PARK CA

VOLTAGE MODE PWM CONTROLLER

PRELIMINARY - February 29, 2000

6

be decoupled directly to GND by a 0.1

µF ceramic ca-

pacitor, trace lengths should be as short as possible.

7) The Current Sense resistor and the divider across it

should form as small a loop as possible, the traces run-

ning back to CS(+) and CS(-) on the SC1103 should

run parallel and close to each other. The 0.1µF capaci-

tor should be mounted as close to the CS(+) and CS(-)

pins as possible.

8) To minimize noise pickup at the sensitive FB pin,

the feedback resistors should both be close to the

SC1103 with the bottom resistor (Rb) returned to

ground at the GND pin.

Under Voltage Lockout

The under voltage lockout circuit of the SC1103 as-

sures that the high-side MOSFET driver outputs remain

in the off state whenever the supply voltage drops be-

low set parameters. Lockout occurs if V

3.8V. Normal operation resumes once V

3.8V.

Fig. 8: 5V to 3.3V @ 8A

TYPICAL APPLICATIONS

Q1

IRL3103S

R4

2.7

R2

1k

D1

MBRB1530CT

R1

10

L1

5.6uH

C9

1500/6.3

C10

1500/6.3

C11

1500/6.3V

C3

1500/6.3V

C2

1500/6.3V

C6

0.1

R7

124

R6

205

C1

0.1

C7

0.01

+3.3V

+5V

GND

C8

0.1

C12

0.1

R5

0.012

R3

1k

GND

VCC

1

Cs(-)

2

Cs(+)

3

PGND

4

DH

5

BST

6

FB

7

GND

8

U1

SC1103

C5

0.1

+12V