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SC338(A)
Ultra Low Output Voltage
Dual Linear FET Controller
POWER MANAGEMENT
Revision: November 12, 2004
Description Features
The SC338(A) is an ultra low output voltage dual power
supply controller designed to simplify power management
for notebook PCs. It is part of Semtech’s Smart LDO
TM
family of products. The SC338(A) has two user
adjustable outputs that can be set anywhere between
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.
SC338(A) features for each output include tight output
voltage regulation (±2.5% over -40°C to +85°C for
SC338, ±1.5% over 0°C to +85°C for SC338A), 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 SC338(A) is available in an
MSOP-10 surface mount package.
±1.5% and ±2.5% reference voltage options
available
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
Notebook PCs
Simple dual power supplies
Typical Application Circuit
Applications
1.05V Enable
R3
20.0k
1.05V Power Good
U1 SC338(A)
1
2
3
4
5
6
7
8
9
10
DRV1
ADJ1
EN1
PGD1
GND PGD2
EN2
ADJ2
DRV2
IN
C1
0.1uF (1)
1.8V +/-5% IN
R4
10.0k
R6 2k (2)
C5
10nF (2)
1.5V Enable
1.05V @ 3A
1.2V +/-5% IN
Notes:
(1) Additional capacitance may be required if far from supply
(2) Optional soft-start components
C6
0.1uF
Q1
IRF7311
4
1
2
3
56
7
8
1.5V @ 1.5A
or similar
1.5V 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
+•=
2R
1R
15.0V
1OUT
+•=
4R
3R
15.0V
2OUT
