Ultra Low Output Voltage
Dual Linear FET Controller
POWER MANAGEMENT
Description
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
Smart LDO
TM
family of products. The SC2738 has two
user adjustable outputs that can be set anywhere be-
tween 0.5V and 3.3V (V
IN
= 12V, anywhere between 0.5V
and 1.8V for V
IN
= 5V) using two external resistors per
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.
SC2738
Features
±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
Applications
Desktop PCs
Graphics cards
Simple dual power supplies
Typical Application Circuit
5V or 12V IN
VIN1
C1
0.1uF (1)
8
1
C3
Q1
7
6
5
3
C4
C2
0.1uF (1)
VIN2
VOUT1
VOUT2
2
4
100uF, 25mOhm POSCAP
R1
11.0k
R5 2k (2)
1
2
U1
DRV1
ADJ1
EN1
PGD1
GND
SC2738
IN
DRV2
ADJ2
EN2
PGD2
10
9
8
7
6
C6
0.1uF
C7
10nF (2)
R6 2k (2)
R3
20.0k
100uF, 25mOhm POSCAP
OUT1 Enable
OUT1 Power Good
3
4
5
R2
10.0k
C5
10nF (2)
OUT2 Enable
OUT2 Power Good
R4
10.0k
R1
V
OUT1
=
0.5
•
1
+
R2
Revision: November 16, 2004
Notes:
(1) Additional capacitance may be required if far from supply
(2) Optional soft-start components
R3
V
OUT 2
=
0.5
•
1
+
R4
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1
SEMTECH [ SEMTECH CORPORATION ]
