POWER MANAGEMENT
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SC431L
Low Voltage Adjustable
Shunt Regulator
Description Features
Revision: May 16, 2008
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.
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
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
Notes:
1) Set V
OUT
according to the following equation:
1RI
2R
1R
1VV
REFREFOUT
+
+=
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:
mA150
V
R
(max)IN
min
≥
(to limit instantaneous turn-on I
Z
)
mA100I
VV
R
(min)OUT
OUT(max)IN
min
+
−
≥
(to limit I
Z
under normal
operating conditions)
Applications
Typical Application Circuit
(1)(2)
