TL431A/KA431A Programmable Shunt Regulator

The TL431 is a three-terminal adjustable shunt regulator that is widely used in Electronics.

• As this is a three terminal device and looks exactly like a transistor, it also requires less PCB space.
• It has three pins, Anode, Cathode and Reference pin.
• For accurate shunt stability the current into the cathode pin must remain >1mA.
• The Reference pin or Adjust pin is used to set the reference voltage using voltage dividers.
• Advantages of TL431 over the Zener diode is that the output voltage can be set to any value between its reference voltage (approximately 2.5 V) to maximum of 36 V and requires only two external resistors.
• Active output circuitry is another advantage that provides a very sharp turn-on characteristic where the Zener diodes fail in many applications, for example - onboard regulation, adjustable power supplies, and switching power supplies.
• In a nutshell, TL431  can be used  as a single voltage reference, error amplifier, voltage clamper comparator with integrated reference.
• TL431 pinout: Package Contains 1x TL431A Programmable Shunt Regulator TL431 Specifications: Adjustable output voltage VREF (2.5V) - 36V Operation From −40°C to 125°C 0.2-Ω Typical Output Impedance Sink-CurrentCapability:1 mA to 100 mA TL431 Applications: Zener DIODE Replacement Adjustable Voltage and Current Referencing Secondary Side Regulation in Fly-back SMPS Voltage Monitoring Comparator As a reference voltage generator TL431 Dimension and footprint: Example Projects on TL431: 100mA Constant Current Generator Additional Resources: TL431 Datasheet.