TL431A 36V 100mA Adjustable Precision Shunt Regulator TO-92

TL431A 36V 100mA Adjustable Precision Shunt Regulator TO-92 is a three-terminal programmable shunt regulator diode that offers excellent thermal stability and high precision for voltage-sensitive circuits. This versatile component provides an adjustable output voltage range from 2.495 V up to 36 V, which you can easily configure using two external resistors. Furthermore, its low dynamic output impedance and fast turn-on characteristics make it a superior replacement for standard Zener diodes in many power supply designs. Consequently, engineers frequently utilize the TL431A to provide a reliable reference voltage or to act as an error amplifier in switching power supplies. Therefore, incorporating this precision regulator into your project ensures stable performance and accurate voltage regulation across varying load conditions.

Key Features:

• Programmable Output Voltage: You can set the output voltage to any value between V_ref (≈ 2.5 V) and 36 V using a simple voltage divider.
• Low Temperature Coefficient: The device maintains a very stable reference voltage across its entire operating temperature range.
• High Sink Current Capability: The internal transistor supports a wide range of sink currents from 1.0 mA to 100 mA.
• Low Output Noise: It provides a clean, low-impedance output that effectively minimizes ripple and noise in power regulation circuits.
• Industry Standard TO-92 Package: The compact through-hole package ensures easy assembly and compatibility with standard breadboards and PCBs.

Technical Specifications:

• Reference Voltage (V_ref): 2.495 V ±1% (A-grade precision)
• Cathode Voltage Range (V_KA): V_ref to 36 V
• Continuous Cathode Current (I_KA): 1.0 mA to 100 mA
• Dynamic Impedance (Z_KA): Typically 0.22 Ω
• Reference Input Current (I_ref): Typically 2 µA (≤ 4 µA max)
• Operating Temperature Range: −40°C to +85°C (Industrial)
• Power Dissipation (P_D): 700 mW (at T_A = 25°C)

Mechanical Specifications:

• Package Type: TO-92 (Plastic Package)
• Lead Material: Tin-plated Alloy 42 or Copper
• Case Material: Molded Plastic (UL 94 V-0 Rated)
• Weight: ≈ 0.18 g

Dimensions:

• Body Height: ≈ 4.58 mm to 5.33 mm
• Body Width: ≈ 4.45 mm to 5.20 mm
• Body Depth: ≈ 3.18 mm to 4.19 mm
• Lead Length: ≈ 12.7 mm minimum
• Lead Pitch: ≈ 1.27 mm (Center to center)

Pinout and Wiring:

• Pin 1 (Reference): Connect this to the center of the external resistor divider to set the desired output voltage.
• Pin 2 (Anode): Connect this pin to the circuit ground (0 V) or the lower potential side.
• Pin 3 (Cathode): Connect this to the positive voltage through a series current-limiting resistor.
• Wiring Note: However, you must ensure the cathode current remains above 1 mA to maintain proper regulation stability.

Datasheet Reference:

• Download Texas Instruments TL431A Datasheet

Commonly Used in:

• Switching Power Supplies (SMPS): Acting as the secondary side error amplifier for isolated feedback loops.
• Linear Regulators: Providing a precise reference for high-current adjustable voltage regulators.
• Battery Chargers: Monitoring voltage levels to prevent overcharging in Li-ion or Lead-Acid batteries.

Applications:

• Precision Voltage Reference: Providing a stable 2.5 V or higher reference for ADCs and DACs.
• Current Shunt Monitors: Operating in conjunction with op-amps to monitor and control current flow.
• Over-Voltage Protection: Crowbar circuits that trigger when a specific voltage threshold is exceeded.
• Voltage Comparators: Used in simple window detectors or threshold monitoring circuits.

Equivalent Models:

• LM431: A common alternative that provides identical pinout and similar electrical characteristics.
• KA431: The version manufactured by Fairchild/ON Semiconductor, often found in power supply modules.
• TLV431: However, note that this is a low-voltage version with a 1.24 V reference, so verify your circuit requirements before swapping.

Package Includes:

• 1 x TL431A 36V 100mA Adjustable Precision Shunt Regulator TO-92