TL431 Shunt Regulator: Where & How to Use TL431？

TL431 Pinout

TL431 Symbol

TL431 Footprint

TL431 3D Model

The TL431 is an adjustable shunt voltage reference with guaranteed temperature stability over the entire operating temperature range. The device temperature range is extended for the automotive version from -40 °C up to +125 °C. The output voltage can be set to any value between 2.5 and 36 V with two external resistors. The TL431 operates with a wide current range from 1 to 100 mA with a typical dynamic impedance of 0.22 Ω.

The TL431 is a programmable shunt regulator with positive and negative reference voltages. It's a Zener diode with a variable voltage rating determined by the value of resistors attached to the reference pin. It's often utilized in isolated power supply circuits as a low-cost reference voltage supplier.

TL431 Circuit

We can see from the TL431's internal circuit layout that it comprises an NPN transistor with an op-amp with an exact voltage of 2.5V on the non-inverting terminal. The IC's cathode and anode terminals are formed by the transistor's collector and emitter pins, respectively. You may now think of the IC as a comparator, with one side having a precise 2.5V and the other side being set through the reference pin.

This feature is particularly useful in switching power supply, where the TL431 can compare the output voltage to the target voltage and offer feedback to manage the switching frequency. In most cases, an optocoupler is employed to isolate the high voltage side of this setup. Apart from that, the IC can be used in a variety of circuits where a Zener diode can be utilized, but only a handful of them.

 AEC-Q100 qualified 

 Adjustable output voltage: 2.5 to 36 V

 Sink current capability: 1 to 100 mA 

 Typical output impedance: 0.22 Ω 

 1% and 2% voltage precision 

 Automotive temp. range -40 °C to +125 °C

• Switch mode Power supplies

• Isolated Power supply circuits

• Voltage comparators

• Current Regulation circuits

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