SC338 Datasheet, PDF (1/14 Pages) Semtech Corporation – Ultra Low Output Voltage Dual Linear FET Controller

POWER MANAGEMENT
Description
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.
Typical Application Circuit
SC338(A)
Ultra Low Output Voltage
Dual Linear FET Controller
Features
‹ ±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
Applications
‹ Notebook PCs
‹ Simple dual power supplies
1.2V +/-5% IN
1.05V @ 3A
C3
100uF, 25mOhm POSCAP
1.05V Enable
1.05V Power Good
V_OUT1
=
0.5
•
1 +

R1
R2


5V or 12V IN
R1
11.0k
R2
10.0k
C1
0.1uF (1)
1
Q1
IRF7311
or similar
87 65
3
2
4
R5 2k (2) ^{U1 SC338(A)}
1
10
DRV1
IN
2
9
ADJ1 DRV2
3
EN1
8
ADJ2
4
7
PGD1 EN2
5
6
GND PGD2
C5
10nF (2)
C2
0.1uF (1)
1.8V +/-5% IN
1.5V @ 1.5A
C4
R6 2k (2)
100uF, 25mOhm POSCAP
R3
20.0k
C6
0.1uF
C7
10nF (2)
R4
10.0k
1.5V Enable
1.5V 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 12, 2004
1
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