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| SC431_08 Datasheet, PDF (1/9 Pages) Semtech Corporation – Adjustable Shunt Regulator | |||
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SC431
Adjustable Shunt Regulator
POWER MANAGEMENT
Description
The SC431 is a three terminal adjustable shunt
regulator with thermal stability guaranteed over
temperature. The output voltage can be adjusted to any
value from 2.5V (VREF) to 30V with two external
resistors. The SC431 has a typical dynamic output
impedance of 0.25â¦. Active output circuitry provides a
very sharp turn on characteristic, making the SC431 an
excellent replacement for zener diodes.
The SC431 shunt regulator is available with four
voltage tolerances (0.5%, 1.0% and 2.0% over T = -40°C
A
to +85°C and 0.5% over TA = -40°C to +125°C) and two
package options (SOT-23-3 and SO-8). This
allows the designer the opportunity to select the
optimum combination of cost and performance for their
application.
Features
 Wide operating current range 130µA to 150mA
 Low dynamic output impedance 0.25 ⦠typ.
 Trimmed bandgap design + 0.5%
 Alternate for TL1431, TL431, LM431 & AS431
 Industrial temperature range
 Available in SOT-23-3 and SO-8 packages.
Also available in Lead-free, 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 VOUT according to the following equation:
VOUT
=
VREF
1 +
ï£
R1
R2


+
IREF
R1
2) Choose the value for R as follows:
⢠The maximum limit for R should be such that the
cathode current, IZ, is greater than the minimum
operating current (130µA) at VIN(MIN).
⢠The minimum limit for R should be such that IZ does
not exceed 150mA under all load conditions, and the
instantaneous turn-on value for IZ does not exceed
200mA. Both of the following conditions must be met:
Rmin
â¥
VIN(max)
200mA
(to limit instantaneous turn-on IZ)
Rmin
â¥
VIN(max) â VOUT
IOUT(min) +150mA
(to limit I under
Z
normal
operating conditions)
Revision: April 23, 2008
1
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