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SC2738

Ultra Low Output Voltage

Dual Linear FET Controller

POWER MANAGEMENT

Revision: November 16, 2004

Description

Features

The SC2738 is an ultra low output voltage dual power

supply controller designed to simplify power management

for desktop PCs and graphics cards. It is part of Semtech’s

user adjustable outputs that can be set anywhere be-

tween 0.5V and 3.3V (V

and 1.8V for V

output.

SC2738 features for each output include tight output

voltage regulation (±3.5% over -40°C to +85°C), enable

controls, open drain power good signals, under-voltage

protection and soft start. The enable pins allow the part

to enter a very low power standby mode. Pulling them

high enables the outputs. The power good pins are open

drain and assert low when the voltage at their

respective adjust pins is below 88% (typ.) of nominal. If

the voltage at the adjust pin is below 50% (typ.) of

nominal, the under-voltage protection circuitry will shut

down that output. The SC2738 is available in an

MSOP-10 surface mount package.

±3.5% reference voltage

Two independant and fully adjustable outputs

Wide supply voltage range permits operation from

5V or 12V rails

Very low quiescent current (500µA typical with both

outputs enabled and 5V input)

Indivdual Enable control for each output

Individual Power Good monitoring and signalling for

each output

Gate drives from input supply enable use of

N-channel MOSFETs

User selectable dropout voltage

Individual under-voltage protection for each output

MSOP-10 surface mount package

Desktop PCs

Graphics cards

Simple dual power supplies

Typical Application Circuit

Applications

OUT1 Enable

R3

20.0k

OUT1 Power Good

U1

SC2738

1

2

3

4

5

6

7

8

9

10

DRV1

ADJ1

EN1

PGD1

GND

PGD2

EN2

ADJ2

DRV2

IN

C1

0.1uF (1)

VIN2

R4

10.0k

R6 2k (2)

C5

10nF (2)

OUT2 Enable

VOUT1

VIN1

Notes:

(1) Additional capacitance may be required if far from supply

(2) Optional soft-start components

C6

0.1uF

Q1

4

1

2

3

5

6

7

8

VOUT2

OUT2 Power Good

C7

10nF (2)

C3

100uF, 25mOhm POSCAP

C4

100uF, 25mOhm POSCAP

R1

11.0k

5V or 12V IN

R5 2k (2)

C2

0.1uF (1)

R2

10.0k











 +

•

=

2

R

1

R

1

5

.

0

V

1

OUT











 +

•

=

4

R

3

R

1

5

.

0

V

2

OUT