SHUNT REGULATOR WITH OPEN
COLLECTOR OR OUTPUT
PRELIMINARY - September 11, 2000
SC4431
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
鈥?
Trimmed bandgap design - initial accuracies to
鈥?
鈥?
鈥?
鈥?
+ 0.5%
40mA drive capability
Wide supply voltage range - 1.5V to 15V
Low supply current - typically 110碌A
Full industrial temperature range
APPLICATIONS
鈥?
Opto driver for very low output voltage isolated
power supplies
ORDERING INFORMATION
Part Number
(1)(2)
Package
SOT-23-5
SC4431CSK-X.TR
Notes:
(1) Where 鈥?X鈥?denotes initial reference voltage toler-
ance. Available options are 鹵0.5% (-.5), 鹵1% (-1) and
鹵2% (-2).
(2) Only available in tape and reel packaging. A reel
contains 3000 devices.
TYPICAL APPLICATION CIRCUIT
T1
VIN
Primary Side
Controller
Secondary Side
Rectification
and Filtering
R1
R2
C1
2V OUT
U1
5.1k
U2
5
OUT
1
VCC
REF
33nF
R3
6.34k
SC4431
4
R4
10k
4N25
C2
22nF
NC
GND
2
3
2V Output Isolated Power Supply
1
漏 2000 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320
SEMTECH
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