SC431_05 Datasheet, PDF (1/9 Pages) Semtech Corporation – Adjustable Shunt Regulator

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 (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 = -40°C
A
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.
Features
‹ 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
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 (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 does not exceed
Z
200mA. Both of the following conditions must be met:
R_min
≥
V_IN(max)
200mA
(to limit instantaneous turn-on I_Z)
R_min
≥
V_IN(max) − V_OUT
I_OUT(min) +150mA
(to limit I_Z under
normal
operating conditions)
Revision: January 13, 2005
1
www.semtech.com