AT431
Low-Voltage Adjustable Precision
Shunt Regulator
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw
Fax: 886-3-563-0879 Email: service@aimtron.com.tw
1
Features
˙ Low-Voltage Operation: Down to 1.24V
˙ 1% Reference-Voltage Tolerance
˙ Adjustable Output Voltage, Vo=V
ref to 12V
˙ Low Operational Cathode Current….50μ A
˙ 0.25Ω Typical Output Impedance
˙ SOT-23-3 , SOT-23-5 and TO-92 Packages
Application
˙ Linear Regulators
˙ Voltage Reference for Power Circuit
Description
The AT431 is low-voltage three-terminal
adjustable voltage reference with specified
thermal stability over applicable commercial
temperature ranges. Output voltage may be set to
any value between V
ref
(1.24V) and 12V with
two external resistors (see Figure 2).

When used with an optocoupler, the AT431 is
ideal voltage reference in isolated feedback
circuits for 1.8V to 12 V switching-mode power
supplies. This device has typical output
impedance of 0.20Ω. Active output circuitry
provides a very sharp turn-on characteristic,
making the AT431 excellent replacements for
low-voltage zener diodes in many applications,
including onboard regulation and adjustable
power supplies.
Block Diagram and Symbol