SC2738 Datasheet PDF - Semtech Corporation


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SC2738
Semtech Corporation

Part Number SC2738
Description Ultra Low Output Voltage Dual Linear FET Controller
Page 13 Pages

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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 LDOTM family of products. The SC2738 has two
user adjustable outputs that can be set anywhere be-
tween 0.5V and 3.3V (VIN = 12V, anywhere between 0.5V
and 1.8V for VIN = 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 LinearwFwwE.DTataCShoeent4Ut.rcoomller
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
VOUT1
=
0.5
1 +
R1
R2

Revision: November 16, 2004
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
24
R5 2k (2) U1 SC2738
1
DRV1
IN
2
ADJ1 DRV2
3
EN1
ADJ2
4
PGD1 EN2
5
GND PGD2
10
9
8
7
6
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
VOUT2
=
0.5 1+
R3
R4

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SC2738
POWER MANAGEMENT
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Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may
affect device reliability.
Parameter
Symbol
Maximum
Units
Input Supply Voltage
Drive Pins
Adjust and Power Good Pins
Enable Pins
Thermal Impedance Junction to Ambient
Thermal Impedance Junction to Case
Operating Ambient Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering) 10 Sec.
ESD Rating (Human Body Model)
Note:
(1) Or VIN, if VIN 5V.
VIN
VDRV
VADJ, VPGD
VEN
θJA
θJC
TA
TJ
TSTG
TLEAD
ESD
-0.3 to +13.2
-0.3 to +8.0
-0.3 to +5.5 (1)
-0.3 to VIN
113
42
-40 to +85
-40 to +150
-65 to +150
300
2
Electrical Characteristics
Unless
specified:
TA
=
25°C,
VIN
=
VEN
=
5V
±
5%,
V (1)
PWR
=
1.5V
±
5%,
0A
IOUT
3A.
Values in bold apply over full operating ambient temperature range.
Parameter
Symbol
Test Conditions
Min
V
V
V
V
°C/W
°C/W
°C
°C
°C
°C
kV
Typ Max Units
IN
Supply Voltage
Quiescent Current
Standby Current
Undervoltage Lockout
VIN
IQ
IQ(OFF)
VIN = 5V
VIN = 12V
Both EN low
Both EN low, VIN = 12V
4.5 13.2 V
500 700 µA
600 900 µA
0.1 1.0 µA
15.0
Start Threshold
Hysteresis
VUVLO
VHYST
VIN rising
VIN falling
3.75
0.50
V
V
2004 Semtech Corp.
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SC2738
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless
specified:
TA
=
25°C,
VIN
=
VEN
=
5V
±
5%,
V (1)
PWR
=
1.5V
±
5%,
0A
IOUT
3A.
Values in bold apply over full operating ambient temperature range.
Parameter
Symbol
Test Conditions
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Min Typ Max Units
EN
Enable Input Threshold
Enable Input Bias Current
VIH
VIL
IEN
ADJ
Output on
Output off
VEN = 0V
VIN = VEN = 5V or 12V
1.3
V
0.7
0 µA
-1 +1
Adjust Input Bias Current
Reference Voltage
DRV
IADJ
VADJ
VADJ = 0.5V
-100
-3.5%
0 +100
0.500 +3.5%
nA
V
Output Current
IDRV Sourcing, startup
(until VTH(PGD) is reached)
10 µA
Sourcing, after startup
0.7 2.0
mA
Sinking
350 700
µA
Output Voltage
VDRV
Under Voltage Protection
Full On, IDRV = 0mA, VIN = 12V
Full On, IDRV = 0mA, VIN = 5V
6.6 6.9
4.70 4.85
V
Trip Threshold (1)
PGD
VTH(UV)
Measured at ADJ pin
40 50 60 %VADJ
Power Good Threshold (2)
Output Logic Low Voltage
Power Good Leakage
Current
VTH(PGD)
VPGD
IPGD
Measured at ADJ pin
VADJ = 0.4V, IPGD = -1mA
VADJ = 0.5V, 0V VPGD VIN
-15 -12
-9 %VADJ
0.4 V
-1 0 +1 µA
Soft Start
Output Rise Time
10% VOUT to 90% VOUT
VOUT = 1.05V
Error Amplifier
tr
CDRV-GND = not placed
CDRV-GND = 10nF
150 µs
850
Open Loop Gain
Gain Bandwidth
AVOL
GBW
52 dB
1 MHz
Notes:
(1) If VTH(UV) is exceeded for longer than 50µs (nom.) the protection circuitry will shut down that output.
(2) During startup only, VTH(PGD) is -6% (typ.), then switches to -12% (typ.).
2004 Semtech Corp.
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POWER MANAGEMENT
Pin Configuration
Top View
(MSOP-10)
SC2738
Ordering Information
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Part Number(1)
Output Voltage
Package
SC2738IMSTRT(2)
Both adj. from
0.5V to 3.3V
MSOP-10
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
Pin Descriptions
Pin Pin Name Pin Function
1 DRV1 Output of regulator #1, output impedance ~ 1k . Drives the gate of an N-channel MOSFET to maintain
VOUT1 set by R1 and R2.
2 ADJ1 Regulator #1 sense input. Used for sensing the output voltage for power good and under-voltage, and
to set the output voltage as follows (refer to application circuit on page 1):
V =OUT(MAX) 3.3V for VIN = 12V, 1.8V for VIN = 5V.
VOUT1
=
0.5
1 +
R1
R2

3 EN1 Active high enable control. Connect to IN if not being used. Do not allow to float.
4 PGD1 Power good signal output for VOUT1. Open drain output pulls low when VOUT1 is below (VOUT1(NOM) -12%).
5 GND Ground.
6 PGD2 Power good signal output for VOUT2. Open drain output pulls low when VOUT2 is below (VOUT2(NOM) -12%).
7 EN2 Active high enable control. Connect to IN if not being used. Do not allow to float.
8 ADJ2 Regulator #2 sense input. Used for sensing the output voltage for power good and under-voltage, and
to set the output voltage as follows (refer to application circuit on page 1):
V =OUT(MAX) 3.3V for VIN = 12V, 1.8V for VIN = 5V.
VOUT 2
=
0.5 1+
R3
R4

9 DRV2 Output of regulator #2, output impedance ~ 1k . Drives the gate of an N-channel MOSFET to maintain
VOUT2 set by R3 and R4.
10 IN +5V or +12V supply.
2004 Semtech Corp.
4
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