SC2738 Datasheet, PDF (1/13 Pages) Semtech Corporation – 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
Ultra Low Output Voltage
Dual Linear FET Controller
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
VIN1
VOUT1
C3
100uF, 25mOhm POSCAP
OUT1 Enable
OUT1 Power Good
V_OUT1
=
0.5
•
1 +

R1
R2


5V or 12V IN
C1
0.1uF (1)
1
Q1
87 65
3
C2
0.1uF (1)
VIN2
VOUT2
C4
R1
11.0k
R2
10.0k
2
4
R5 2k (2) ^{U1 SC2738}
1
10
DRV1
IN
2
9
ADJ1 DRV2
3
EN1
8
ADJ2
4
7
PGD1 EN2
5
6
GND PGD2
C5
10nF (2)
R6 2k (2)
100uF, 25mOhm POSCAP
R3
20.0k
C6
0.1uF
C7
10nF (2)
R4
10.0k
OUT2 Enable
OUT2 Power Good
Notes:
(1) Additional capacitance may be required if far from supply
(2) Optional soft-start components
V_OUT2
=
0.5 • 1+

R3
R4


Revision: November 16, 2004
1
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