The TL431 is a three-terminal adjustable shunt regulator. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors.

TL431 has a typical output impedance of 0.2 Ω. Active output circuitry provides a very sharp turn-on characteristic, making these devices excellent replacements for Zener diodes in many applications, such as onboard regulation, adjustable power supplies, and switching power supplies. 

Product feature:

• Reference voltage tolerance at 25°C

– 0.5% (B grade)

– 1% (A grade)

– 2% (Standard grade)

• Adjustable output voltage: Vref to 36 V

• Operation from −40°C to 125°C

• Low output noise

• 0.2-Ω Typical output impedance

• Sink-current capability: 1 mA to 100 mA

Applications:

• Adjustable voltage and current referencing

• Secondary side regulation in flyback SMPSs

• Zener replacement

• Voltage monitoring

• Comparator with integrated reference

• Hash board maintenance