Page 1
© 1999 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
DUAL LINEAR CONTROLLER
SC1538
PRELIMINARY - October 5, 1999
1
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
The SC1538 is a dual power supply controller designed
to simplify power management on motherboards. It is
part of Semtech’s Smart LDO™ family of products.
The SC1538CS15/18 can provide a 1.818V power supply for the I/O plane and a 1.515V power supply for the
GTL+ and AGP planes. The SC1538CS25/25 can provide two 2.525V supplies for clock and memory.
SC1538 features include Enable controls for each linear FET controller and over current protection. Over
current protection is provided by feedback to the sense
pins. If any output drops below 1V (typical) for greater
than 4ms (typical), that output will shut down.
The SC1538 is available in a SO-8 surface mount
package.
FEATURES
•
Dual power supplies
•
1.515V Supply for GTL+ and AGP planes/1.818V
Supply for chipset I/O and memory termination
•
Dual 2.525V supplies for clock and memory
•
Individual Enable control of each supply
•
Over current protection
APPLICATIONS
•
Motherboards
•
Simple dual power supplies
ABSOLUTE MAXIMUM RATINGS
Parameter Symbol Maximum Units
Input Supply Voltage VIN -0.5 to +15 V
Input Pins -0.5 to +7 V
Operating Temperature
Range
T
A
0 to +70 °C
Operating Junction
Temperature
T
J
0 to +125 °C
Storage Temperature
Range
T
STG
-65 to +150 °C
Lead Temperature
(Soldering) 10 Sec
T
LEAD
300 °C
Thermal Temperature
Junction to Ambient
θ
JA
130 °C/W
Thermal Impedance
Junction to Case
θ
JC
47 °C/W
ESD Rating ESD 2 kV
ORDERING INFORMATION
Part Number
(1)
Output Voltages Package
SC1538CS15/18 1.515V and 1.818V SO-8
SC1538CS25/25 2.525V and 2.525V SO-8
Note:
(1) Add suffix ‘TR’ for tape and reel packaging.
BLOCK DIAGRAM
PIN CONFIGURATION
(SO-8)
Top View
Page 2
© 1999 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
DUAL LINEAR CONTROLLER
SC1538
PRELIMINARY - October 5, 1999
2
PIN DESCRIPTION
Pin Pin Name Pin Function
1 DRV1 Output of regulator #1. Drives the gate of an N-channel MOSFET to maintain 1.818V/
2.525V.
2 SNS1 Regulator #1 Sense input. Use as a remote sense to the source of the N-channel MOSFET
(Output 1).
3 EN1 Active high enable control with internal pullup. Output of regulator #1 turns off when EN1 is
taken low.
4 GND Ground
5 EN2 Active high enable control with internal pullup. Output of regulator #2 turns off when EN2 is
taken low.
6 SNS2 Regulator #2 Sense input. Use as a remote sense to the source of the N-channel MOSFET
(Output 2).
7 DRV2 Output of regulator #2. Drives the gate of an N-channel MOSFET to maintain 1.515V/
2.525V.
8 VIN +12V Supply.
APPLICATION CIRCUIT
1.818V / 2.525V OUT
1.818V / 2.525V ENABLE
3.3V IN 12V IN
1.515V / 2.525V OUT
1.818V / 2.525V ENABLE
Q1
PHB11N06LT
Q2
PHB11N06LT
U1
SC1538
1
2
3
4 5
6
7
8
DRV1
SNS1
EN1
GND EN2
SNS2
DRV2
VIN
C1
100uFC2100uF
C3
100uF
C4
100uF
C5
100uFC6100uF
C7
0.1uF
R1
10k
R2
10k
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© 1999 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
DUAL LINEAR CONTROLLER
SC1538
PRELIMINARY - October 5, 1999
3
NOTES:
(1) See Application Circuit
(2) Connected to FET drains.
ELECTRICAL CHARACTERISTICS
Unless specified, TA = 25°C. Values in
bold
apply over full operating temperat ure range.
Parameter Symbol Test Conditions MIN TYP MAX Units
VIN
Supply Voltage VIN
11.28
12.00
12.72
V
Quiescent Current I
Q
Both EN High 2 3 mA
4
One or both EN Low 1.5 2.0 mA
2.5
Undervoltage Lockout
Start Threshold UVLO
7
8
9
V
Enable
Enable Pin Current I
EN
Input = Low 50 100 µA
150
Threshold Voltage V
TH
VEN rising
1.6 2.3
V
Hysteresis V
HYST
100
180
300
mV
Enable Delay Time
(1)
t
D(ON)
EN = Low to High, measured from
EN = V
TH
to 10% DRV
500 ns
Disable Delay Time
(1)
t
D(OFF)
EN = High to Low, measured from
EN = V
TH
to 90% DRV
150 ns
DRV
Output Current I
DRV
5
10 mA
Output Voltage V
DRV
Full On
9.0
10.5 V
Rise Time
(1)
t
r
EN = Low to High, measured from
EN = V
TH
to 90% DRV
1.6 ms
Fall Time
(1)
t
f
550 ns
Output Voltage Regulation
Output Voltage
(1)
VO
3.0V ≤ V
FET
(2)
≤ 3.6V, 1mA ≤ IO ≤ 1A
-1.5% VO +1.5% V
-2.5% +2.5%
Overcurrent Protection
Trip Threshold V
OC
-20%
1.00
+15%
V
Power-up Output Short
Circuit Immunity
1560ms
Output Short Circuit Glitch
Immunity
0.5 4 6 ms
Control Section
Bandwidth DRV = 9V, THD = 5%, C
L
= 600pF 5 MHz
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© 1999 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
DUAL LINEAR CONTROLLER
SC1538
PRELIMINARY - October 5, 1999
4
OUTLINE DRAWING - SO-8
JEDEC
REF: MS-012AA
LAND PATTERN - SO-8
ECN99-633 - 10-5-99
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