SC4431_03 Datasheet, PDF (1/8 Pages) Semtech Corporation – Shunt Regulator With Open Collector Output

SC4431
Shunt Regulator With
Open Collector Output
POWER MANAGEMENT
Description
The SC4431 is a four terminal device for regulating an
isolated power supply with output voltages down to 1.5V.
It is intended to be used as a replacement for three
terminal shunt regulators such as SC431L where the
output voltage is too low for the device to function in
conjunction with an opto-isolator. SC4431 achieves this
by having seperate supply and output pins, allowing the
output to sink current at voltages as low as 0.1V, while
the supply pin still has sufficient voltage for the device to
function. In this way, allowing for a 1.4V drop through an
opto-isolator diode, regulation down to 1.5V out can be
achieved.
The SC4431 shunt regulator is available with three
initial 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
‹ Open Collector output drives Optoisolator with
as little as 1.5V input voltage
‹ Trimmed bandgap design - initial accuracies
to + 0.5%
‹ 40mA drive capability
‹ Regulates output as low as 50mV
‹ Wide supply voltage range - 1.5V to 15V
‹ Low supply current - typically 110µA
‹ Full industrial temperature range
‹ SOT-23 5 lead package
Applications
‹ Telecom Power Supplies
‹ Opto driver for very low output voltage (1.5V)
isolated power supplies
‹ Battery operated applications
‹ Point of use power supplies
Typical Application Circuit
2V Output Isolated Power Supply
T1
Primary Side
VIN
Controller
Secondary Side
Rectification
and Filtering
R1
R2
2V OUT
C1
U1
4N25
C2
22nF
5.1k
C3
33nF
SC4431
5
OUT
1 VCC
4
REF
3
NC
2 GND
R3
6.34k
R4
10k
Revision September 9 ,2003
1
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