SC431L_07 Datasheet, PDF (1/10 Pages) Semtech Corporation – 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
Low Voltage Adjustable
Shunt Regulator
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:
V_OUT
=
V_REF
1 +

R1
R2


+
I_REF
R1
2) Choose the value for R as follows:
• The maximum limit for R should be such that the
cathode current, I , is greater than the minimum
Z
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 does not exceed
Z
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: October 4, 2007
1
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