TL431: Adjustable Precision Shunt Regulator – Features, Uses, and Specifications

 

The TL431 is a widely used programmable shunt voltage reference known for its accuracy, versatility, and low cost. It is often found in power supplies, voltage monitoring circuits, and as a feedback component in switching regulators. With its ability to maintain a stable reference voltage over a wide range of temperatures and operating conditions, the TL431 has become a go-to component in both analog and digital designs.

 

What is the TL431?

 

The TL431 is a three-terminal adjustable precision shunt regulator that acts similarly to a programmable Zener diode. It provides a precise 2.5V reference that can be adjusted up to 36V using two external resistors.

 

It is widely used in switching power supplies, battery chargers, LED drivers, and voltage monitoring systems.

 

Key Features of TL431

 

·        Adjustable Output Voltage: 2.5V to 36V

·        High Accuracy: ±1% (A version), ±0.5% (B version)

·        Low Output Impedance: Less than 0.2Ω typical

·        Wide Operating Temperature Range: -40°C to +125°C

·        Sink Current Capability: 1 mA to 100 mA

·        Low Dynamic Output Resistance: Ideal for voltage regulation

·        Available Packages: TO-92, SOT-23, SO-8, and more

·        Excellent Stability: Over time and temperature

 

 

TL431 Technical Specifications

 

Parameter                             TL431                    

Reference Voltage (Vref)   2.495V (typical)             

Adjustable Range                 2.5V to 36V                  

Output Current                     1 mA to 100 mA               

Voltage Tolerance               ±0.5% (TL431B), ±1% (TL431A) 

Operating Temp. Range     -40°C to +125°C              

Output Impedance               < 0.2Ω (typical)             

Packages Available               TO-92, SOT-23, SOIC-8        

 

 

TL431 Circuit Diagram (Voltage Reference Setup)

 

 

Where:

- Vout = Vref × (1 + R1/R2)

 

This configuration allows you to set any output voltage between 2.5V and 36V by choosing appropriate resistor values.

 

Common Applications of TL431

 

1.  Switching Power Supply Feedback

  Used in feedback loops of SMPS (flyback, buck, boost) for precise voltage regulation.

 

2. Battery Chargers

   Regulates the output voltage to prevent overcharging.

 

3. Overvoltage and Undervoltage Protection

   Detects faults in voltage levels and triggers protection mechanisms.

 

4. LED Drivers

   Provides a constant reference for current control circuits in LED lighting.

 

5. Precision Voltage References

   Acts as a stable reference in analog circuits, ADCs, and DACs.

 

6. Computer Power Supplies

   Helps maintain tight regulation on multiple voltage rails.

 

7. Telecom and Industrial Equipment

   Provides reference stability in harsh environments.

 

Why Choose TL431?

 

Precision Control: Thanks to its adjustable output and tight voltage tolerance, it allows for fine-tuned voltage references.

Cost Effective: Offers excellent performance at a very affordable price.

Versatile Applications: Found in both analog and digital circuits across consumer, industrial, and automotive sectors.

Reliable Performance: Maintains accuracy over time and temperature changes.

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