TL431ASF

Overview

The TL431ASF is a three-terminal adjustable precision shunt regulator manufactured by TAEJIN (HTC Korea). It operates within a temperature range of -40°C to +125°C and features a guaranteed reference voltage tolerance of 1%. The device allows programmable output voltages from the internal VREF (2.495V) up to 40V using two external resistors. It offers a typical dynamic output impedance of 0.2Ω, a cathode current range of 0.5mA to 100mA for regulation, and an equivalent full-range temperature coefficient of 50PPM/°C. The component is supplied in an SOT-23-3L package.

Feature Summary

• Programmable output voltage capability extending up to 40V via external resistor networks
• Temperature compensated operation ensuring stability across the full industrial temperature range
• Low dynamic output impedance providing sharp turn-on characteristics suitable for Zener diode replacement

Applications

• Shunt Regulator
• Precision High-Current Series Regulator
• High-Current Shunt Regulator
• Crowbar Circuit
• PWM Converter With Reference

Procurement Notes

Verify that the ordering suffix 'SF' corresponds specifically to the SOT-23-3L tape and reel packaging configuration as defined in the manufacturer's ordering information table. Confirm the 'A' designation indicates the required 1% reference voltage tolerance level. Ensure the procurement source provides documentation matching the HTC Korea datasheet revision R2.0.1 dated May 2023 to guarantee accurate electrical parameter alignment.

Selection Notes

Select this component when a precise, adjustable voltage reference is required in a compact surface-mount footprint. The 1% tolerance variant is appropriate for applications demanding tighter accuracy than standard 2% or 5% devices. Consider the SOT-23-3L package constraints regarding thermal dissipation and pin pitch compatibility during PCB layout design. Evaluate the 0.5mA minimum cathode current requirement against the specific load conditions of the target circuit.

Part Context

This device belongs to the TL431 family of programmable precision shunt regulators produced by TAEJIN Technology. The family includes variants with different tolerances (C, A, and standard) and packages (TO-92, SOT-89, SOT-23). The TL431 series serves as a direct functional replacement for traditional Zener diodes in many linear and switching power supply designs, offering superior temperature stability and lower noise performance.

Replacement Considerations

Direct replacements include other manufacturers' TL431A parts in SOT-23 packages, such as TI's TL431AIMF or NXP's TL431ACQ. Verify pinout compatibility and ensure the substitute part meets the 40V maximum cathode voltage rating and the -40°C to +125°C operating temperature range specified for the original device.

FAQ

What is the minimum cathode current required for the TL431ASF to maintain regulation?

The device requires a minimum cathode current of 0.5mA to regulate properly when the cathode voltage equals the reference voltage.

How does the 'A' suffix in TL431ASF affect the reference voltage tolerance?

The 'A' suffix indicates a 1% tolerance for the reference voltage, resulting in a VREF range of 2.470V to 2.520V at 25°C, compared to 2% for the standard version.