Low Voltage Adjustable
Shunt Regulator
POWER MANAGEMENT
Description
The SC431L is a three terminal adjustable shunt
regulator with thermal stability guaranteed over
temperature. The output voltage can be adjusted to any
value from 1.24V (V
REF
) to 20V with two external
resistors. The SC431L has a typical dynamic output
impedance of 0.05Ω. Active output circuitry provides a
very sharp turn on characteristic, making the SC431L an
excellent replacement for zener diodes.
The SC431L shunt regulator is available with four volt-
age tolerances (0.25%, 0.5%, 1.0% and 2.0%), two
operating temperature ranges (commercial and indus-
trial) and two package options (SOT-23-3 and SOT-23-
5). This allows the designer the opportunity to select the
optimum combination of cost and performance for their
application.
SC431L
Features
Low voltage operation (down to 1.24V)
Wide operating current range 100µA to 100mA
Low dynamic output impedance 0.05
Ω
typ.
Trimmed bandgap design ± 0.25%
Upgrade for TLV431A
SOT-23-3 and SOT-23-5 packages. Also available in
Lead-free package, fully WEEE and RoHS compliant
Applications
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
Typical Application Circuit
(1)(2)
Notes:
1) Set V
OUT
according to the following equation:
R1
V
OUT
=
V
REF
1
+
+
I
REF
R1
R2
2) Choose the value for R as follows:
•
The maximum limit for R should be such that the
cathode current, I
Z
, is greater than the minimum
operating current (100µA) at V
IN(MIN)
.
•
The minimum limit for R should be such that I
Z
does
not exceed 100mA under all load conditions, and the
instantaneous turn-on value for I
Z
does not exceed
150mA. Both of the following conditions must be met:
R
min
≥
V
IN (max)
150 mA
(to limit instantaneous turn-on I
Z
)
R
min
≥
V
IN (max)
−
V
OUT
I
OUT (min)
+
100 mA
(to limit I
Z
under normal
operating conditions)
Revision: May 16, 2008
1
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