TL431A / KA431A Programmable Shunt Regulator – TO-92 Package

TL431A / KA431A Programmable Shunt Regulator – TO-92 Package

The TL431A (or KA431A) is a versatile 3-terminal programmable shunt voltage regulator, widely used in power supply designs and voltage regulation circuits. It functions as an adjustable Zener diode with a reference voltage of 2.5V, and can be set with just two external resistors to regulate voltages from 2.5V to 36V.

Unlike conventional Zener diodes, the TL431A provides a sharp turn-on behavior and excellent temperature stability. Its compact TO-92 package allows space-efficient designs, making it ideal for various electronics projects including SMPS, battery chargers, reference voltage generators, and analog control systems.

🔹 Key Features:

• Adjustable Output Voltage: 2.5V to 36V

• Reference Voltage: 2.495V ±0.5%

• Sink Current Range: 1 mA to 100 mA

• Low Output Impedance: 0.2Ω typical

• Operating Temperature Range: −40°C to +125°C

• TO-92 3-pin package for easy prototyping

• Excellent thermal and long-term stability

📊 Technical Specifications:

🧰 Applications:

• Zener diode replacement

• Adjustable voltage regulation

• Secondary side regulation in flyback SMPS

• Voltage and current referencing

• Overvoltage protection

• Comparator with reference

• Constant current source

📦 Package Includes:

• 1 x TL431A / KA431A Programmable Shunt Regulator (TO-92)

📏 Dimensions (Approx.):

• Package: TO-92

• Height: ~5mm

• Width: ~4mm

• Lead Pitch: 1.27mm (standard TO-92 footprint)

📚 Resources:

• TL431 Datasheet (TI)

• Example Circuit: 100mA Constant Current Generator

• Additional Use Cases: Voltage Clamping, Feedback Control in SMPS