POWER MANAGEMENT
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SC431
Adjustable Shunt Regulator
Revision: April 23, 2008
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 (V
REF
) to 30V with two external
resistors. The SC431 has a typical dynamic output
impedance of 0.25Ω. 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
A
= -40°C
to +85
°C and 0.5% over T
A
= -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.
Linear Regulators
Adjustable Supplies
Switching Power Supplies
Battery Operated Computers
Instrumentation
Computer Disk Drives
Wide operating current range 130µA to 150mA
Low dynamic output impedance 0.25 Ω 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.
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 (130µA) at V
IN(MIN)
.
• The minimum limit for R should be such that I
Z
does
not exceed 150mA under all load conditions, and the
instantaneous turn-on value for I
Z
does not exceed
200mA. Both of the following conditions must be met:
mA200
V
R
(max)IN
min
≥
(to limit instantaneous turn-on I
Z
)
mA150I
VV
R
(min)OUT
OUT(max)IN
min
+
−
≥
(to limit I
Z
under normal
operating conditions)
Applications
Typical Application Circuit
(1)(2)
FeaturesDescription
