SC2738 Semtech Corporation, SC2738 Datasheet

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SC2738

Manufacturer Part Number
SC2738
Description
Ultra Low Output Voltage Dual Linear FET Controller
Manufacturer
Semtech Corporation
Datasheet

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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
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.
Revision: November 16, 2004
POWER MANAGEMENT
Description
Typical Application Circuit
OUT1 Power Good
V
OUT1 Enable
OUT
VOUT1
100uF, 25mOhm POSCAP
1
VIN1
TM
0
5 .
family of products. The SC2738 has two
IN
C3
= 5V) using two external resistors per
1
R
R
2
1
IN
= 12V, anywhere between 0.5V
R1
11.0k
R2
10.0k
Notes:
(1) Additional capacitance may be required if far from supply
(2) Optional soft-start components
C1
0.1uF (1)
C5
10nF (2)
Q1
1
R5 2k (2)
2
3
4
5
8
2
1
U1
DRV1
ADJ1
EN1
PGD1
GND
7
SC2738
6
DRV2
PGD2
ADJ2
EN2
1
5
IN
Features
Applications
4
9
8
6
10
7
±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
3
5V or 12V IN
C6
0.1uF
Dual Linear FET Controller
R6 2k (2)
Ultra Low Output Voltage
C7
10nF (2)
R3
20.0k
R4
10.0k
C2
0.1uF (1)
V
OUT
www.DataSheet4U.com
100uF, 25mOhm POSCAP
2
0
5 .
C4
OUT2 Enable
OUT2 Power Good
www.semtech.com
SC2738
VIN2
VOUT2
1
R
R
3
4

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SC2738 Summary of contents

Page 1

... 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 part of Semtech’s Smart LDO family of products. The SC2738 has two TM user adjustable outputs that can be set anywhere be- tween 0 ...

Page 2

... SC2738 www.DataSheet4U.com PRELIMINARY ...

Page 3

... SC2738 www.DataSheet4U.com ...

Page 4

... SC2738 www.DataSheet4U.com PRELIMINARY ...

Page 5

... POWER MANAGEMENT Block Diagram 2004 Semtech Corp. (0.94 VBG at start-up) 5 SC2738 www.DataSheet4U.com (0.94 VBG at start-up) www.semtech.com ...

Page 6

... POWER MANAGEMENT Applications Infomation Theory Of Operation The SC2738 dual linear FET controller provides a simple way to drive two N-channel MOSFETs to produce tightly regulated output voltages from one or two available, higher, supply voltages. It takes its power from either 12V supply, drawing typically 500µA while operating ...

Page 7

... OUT DRAIN OUT DS(ON) If the supply to the SC2738 IN pin comes up before the supply to the MOSFET drain, then that output should be enabled as the supply to the MOSFET drain is applied - the Power Good signal for this rail would be ideal. If the power supply to the MOSFET drain comes up before the ...

Page 8

... DS(ON Table 1: Recommended Resistor Values For SC2738 Design Example Goal: 1.5V±5% static and ±7% transient @ from 2.5V±5% and 5V±5% Total window for DC error and ripple is ±75mV. Total window for transient is ±105mV. Since this device is linear, and assuming that it has been designed to not ever enter dropout not have ripple on the output ...

Page 9

... I OUT ( MAX ) Obviously 12V rail is available to power the SC2738, the number of FET options increases dramatically. 2004 Semtech Corp. Layout Guidelines The advantages of using the SC2738 to drive external MOSFETs are a) that the bandgap reference and control circuitry are in a die that does not contain high power ...

Page 10

... Drive Pin Output Current (Sourcing) at Startup vs. Junction Temperature vs. Input Voltage < V ADJ TH(PGD 100 125 -50 -25 10 SC2738 www.DataSheet4U.com PRELIMINARY vs. Input Voltage = 12V 100 T (°C) J vs. Junction Temperature ...

Page 11

... Power Good Logic Low Output Voltage 200 175 V = 0.4V ADJ I = -1mA PGD 150 125 100 100 125 -50 -25 11 SC2738 www.DataSheet4U.com V = 12V 100 T (°C) J vs. Junction Temperature = 100 T (°C) J vs. Junction Temperature ...

Page 12

... 0.01A to 2.51A to 0.01A OUT 100µF, 25m OUT R = 20m DROOP Trace 1: V OUT Trace 2: not connected Trace 3: 1.2V in, 50mV/div., offset 1V Trace 4: load FET drain Timebase: 20µs/div. Load rise/fall times 12 SC2738 www.DataSheet4U.com PRELIMINARY , 20mV/div., offset 1V /µs 35A www.semtech.com ...

Page 13

... SEE DETAIL SIDE VIEW AND - DETERMINED AT DATUM PLANE -H- DIMENSIONS DIM INCHES (.161 .098 .020 X .011 Y .063 Z .224 Y Semtech Corporation Power Management Products Division 200 Flynn Road, Camarillo, CA 93012 13 SC2738 www.DataSheet4U.com MILLIMETERS NOM MAX - - .043 1.10 - .006 0.00 0.15 - .037 0.75 0.95 .011 0.17 - 0.27 - .009 0.08 0.23 .122 2.90 3.00 3 ...

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