2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
SC4431
PRELIMINARY - September 11, 2000
1
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
The SC4431 is a four terminal device for regulating an
isolated power supply with very low output voltage.
It is intended to be used as a replacement for three ter-
minal shunt regulators such as SC431L where the out-
put voltage is too low for them to function in conjunc-
tion with an opto-isolator. It achieves this by having
seperate supply and output pins, allowing the output to
sink current at voltages as low as 0.2V, while the sup-
ply pin still has sufficient voltage for the device to func-
tion. In this way, allowing for a 1.6V drop through an
opto-isolator diode, regulation down to 1.8V out can be
achieved.
The SC4431 shunt regulator is available with three ini-
tial reference voltage accuracies (0.5%, 1.0% and
2.0%) in the space saving 5-lead SOT-23 package.
The three voltage tolerances allow the designer the
opportunity to select the proper cost/tolerance for their
application.
FEATURES
=
Trimmed bandgap design - initial accuracies to
+
0.5%
=
40mA drive capability
=
Wide supply voltage range - 1.5V to 15V
=
Low supply current - typically 110A
=
Full industrial temperature range
APPLICATIONS
=
Opto driver for very low output voltage isolated
power supplies
ORDERING INFORMATION
Part Number
(1)(2)
Package
SC4431CSK-X.TR
SOT-23-5
Notes:
(1) Where "-X" denotes initial reference voltage toler-
ance. Available options are 0.5% (-.5), 1% (-1) and
2% (-2).
(2) Only available in tape and reel packaging. A reel
contains 3000 devices.
TYPICAL APPLICATION CIRCUIT
2V OUT
R1
U1
4N25
U2
SC4431
1
2
3
4
5
VCC
GND
NC
REF
OUT
R4
10k
R3
6.34k
C2
22nF
C1
33nF
R2
5.1k
VIN
T1
Primary Side
Controller
Secondary Side
Rectification
and Filtering
2V Output Isolated Power Supply
2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
SC4431
PRELIMINARY - September 11, 2000
2
ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol
Maximum
Units
Input Supply Voltage
V
CC
-0.5 to +16
V
Output Voltage
V
OUT
-0.5 to V
CC
V
Reference Voltage
V
REF
-0.5 to +4
V
Continuous Output Current
I
OUT
40
mA
Reference Input Current
I
REF
5
mA
Operating Ambient Temperature Range
T
A
-40 to +85
C
Operating Junction Temperature Range
T
J
-40 to +150
C
Storage Temperature Range
T
STG
-65 to +150
C
Thermal Impedance Junction to Ambient
JA
256
C/W
Thermal Impedance Junction to Case
JC
81
C/W
Power Dissipation at T
A
= 25C
P
D
475
mW
Lead Temperature (Soldering) 10 seconds
T
LEAD
300
C
ESD Rating (Human Body Model)
ESD
2
kV
ELECTRICAL CHARACTERISTICS
Unless specified, T
A
= 25C, V
CC
= 2V, I
OUT
= 2mA. Values in bold apply over full operating temperature range.
Parameter
Symbol
Test Conditions
MIN
TYP MAX
Units
VCC
Input Supply Voltage
V
CC
1.5
15
V
Input Supply Current
I
CC
V
REF
= V
OUT
110
200
A
Off State Input Supply Current
I
CC(OFF)
V
REF
= 1.187V, V
OUT
= 2V
65
100
A
150
REF
Reference Voltage
V
REF
SC4431-.5, V
REF
= V
OUT
1.219 1.224 1.231
V
1.207
1.243
SC4431-1, V
REF
= V
OUT
1.212 1.224 1.236
V
1.200
1.250
SC4431-2, V
REF
= V
OUT
1.200 1.224 1.250
V
1.187
1.261
Change in V
REF
due to change
V
CC
= 1.5V to 15V
8
15
mV
in V
CC
20
Change in V
REF
due to change
I
OUT
= 0.1mA to 40mA
8
28
mV
in I
OUT
36
CC
REF
dV
dV
OUT
REF
dI
dV
2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
SC4431
PRELIMINARY - September 11, 2000
3
ELECTRICAL CHARACTERISTICS (Cont.)
Unless specified, T
A
= 25C, V
CC
= 2V, I
OUT
= 2mA. Values in bold apply over full operating temperature range.
Parameter
Symbol
Test Conditions
MIN
TYP MAX
Units
REF (Cont.)
Reference Input Current
I
REF
0.1mA
I
OUT
10mA
0.3
0.5
A
1.0
OUT
Saturation Voltage
V
OUT(SAT)
I
OUT
= 5mA, I
CC
= 500A
50
75
mV
100
V
REF
= 1.261V, I
OUT
= 40mA
275
300
mV
400
Off State Output Current
I
OUT(OFF)
V
REF
= 1.187V, V
OUT
= 2V
0.5
1
A
10
2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
SC4431
PRELIMINARY - September 11, 2000
4
PIN DESCRIPTION
Pin
Pin Name Pin Function
1
VCC
This is the input supply pin for the IC.
2
GND
Logic and power ground.
3
NC
No connection.
4
REF
This is connected to the non-inverting input of the error amplifier.
5
OUT
This is the output pin of the device, essentially an open collector.
BLOCK DIAGRAM
PIN CONFIGURATION
SOT-23 -5 Lead (Top View)
2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
SC4431
PRELIMINARY - September 11, 2000
5
ECN 00-1315
DEVICE OUTLINE - SOT-23-5
LAND PATTERN - SOT-23-5
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