Texas Instruments TL431LIAIDBZR

Overview

TL431LIAIDBZR from Texas Instruments is a three-terminal adjustable shunt regulator with 1% initial reference voltage tolerance at 25°C, 2.495 V nominal Vref, 0.3 Ω typical dynamic impedance, and operation across −40°C to +85°C (I-temp grade). It functions as a precision voltage reference, error amplifier, or comparator in secondary-side regulation of flyback SMPS and onboard voltage monitoring circuits.

For engineers reviewing the TL431LIAIDBZR datasheet, TL431LIAIDBZR pinout, TL431LIAIDBZR application, or TL431LIAIDBZR equivalent, key selection criteria include reference accuracy over temperature, cathode current capability (1–15 mA), low IREF (≤0.4 µA), thermal drift (≤17 mV over −40°C to +85°C), and SOT-23 package compatibility for space-constrained power management designs.

Technical Context

The TL431LIAIDBZR integrates an accurate 2.495 V bandgap reference and high-gain op-amp in a single silicon die, enabling closed-loop shunt regulation via external resistive feedback between cathode and reference pins. Its Darlington output stage delivers up to 15 mA sink current while maintaining 0.3 Ω dynamic impedance at 1 mA cathode current.

It operates in two primary functional modes: open-loop comparator mode (with internal reference) requiring ≥1 mA cathode current for stable switching response, and closed-loop shunt regulator mode where feedback forces the reference pin to Vref, adjusting cathode voltage from 2.495 V to 36 V. Temperature drift is specified as 17 mV max over −40°C to +85°C (I-temp).

Key Specifications

Pinout & Package

SOT-23 (DBZ) package: 3-pin surface-mount, 2.90 mm × 1.30 mm body size, gull-wing leads, JEDEC MO-178AC compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt regulator applications.

Compared with TL431CDBZR, TL431LIAIDBZR provides guaranteed operation down to −40°C - essential for outdoor or automotive electronics - while maintaining identical pinout and electrical interface. Against TLVH431IDBVR, it offers superior accuracy (1% vs 2.5%), higher reference voltage (2.495 V vs 1.24 V), and true 3-pin SOT-23 compatibility, avoiding layout redesign.

Availability

TL431LIAIDBZR is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, and telecom infrastructure equipment requiring stable component supply across extended temperature ranges.

Supply support for TL431LIAIDBZR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in power management, signal chain, and high-reliability components.

The TL431LIAIDBZR belongs to TI's precision shunt regulator product line, designed specifically for high-accuracy voltage referencing and error amplification in isolated power conversion, voltage supervision, and current regulation systems.

FAQ

What is the maximum cathode voltage rating for TL431LIAIDBZR?

The TL431LIAIDBZR has an absolute maximum cathode-to-anode voltage (VKA) rating of 37 V. Its recommended operating range is 2.495 V to 36 V. Exceeding 37 V risks permanent damage, and operation above 36 V violates recommended conditions per the datasheet. The device achieves stable regulation only when VKA remains ≥ Vref (2.495 V) and within this specified window. Always verify voltage margins in your application's worst-case transient conditions before finalizing the TL431LIAIDBZR design.

Does TL431LIAIDBZR require an external capacitor for stability?

No, TL431LIAIDBZR is internally compensated and does not require an external capacitor between cathode and anode for basic stability in most shunt regulator configurations. However, if output capacitance is added (e.g., for noise filtering), its value must be selected carefully - Figure 12 in the datasheet defines stability boundaries versus load capacitance and cathode voltage. Uncontrolled capacitance can induce oscillation, especially at higher VKA or with low ESR ceramics. For TL431LIAIDBZR implementations demanding high-frequency immunity, consult TI's SLVA987 and SNOAA00 application notes to validate capacitor selection.

How does the reference input current (IREF) affect TL431LIAIDBZR accuracy?

The reference input current (IREF) of TL431LIAIDBZR - max 0.4 µA at 25°C - flows into the REF pin and creates a voltage drop across upstream resistors in the feedback divider. This introduces a systematic error in the sensed voltage. For example, with a 100 kΩ top resistor, IREF causes up to 40 mV offset, degrading effective accuracy beyond the 1% Vref tolerance. To minimize this, use lower-value resistors (e.g., ≤10 kΩ total divider) or compensate mathematically in design. The TL431LIAIDBZR's low IREF specification directly enables higher overall system accuracy compared to older TL431 variants with higher IREF.

Can TL431LIAIDBZR be used as a comparator, and what are the key requirements?

Yes, TL431LIAIDBZR functions as a comparator with integrated 2.495 V reference in open-loop mode. Key requirements include supplying ≥1 mA cathode current (IKA) to ensure sufficient open-loop gain and fast response, and providing ≥10% overdrive voltage (e.g., >2.75 V on REF for A-grade) to avoid slow transitions. Its output is open-collector: low-state voltage is ~2 V (suitable for 5 V logic), high-state equals VSUP. For 3.3 V or 1.8 V logic interfaces, add a resistive divider. TL431LIAIDBZR's comparator use avoids needing separate reference and comparator ICs - confirmed in TI application note SLVA987.

What is the thermal performance of TL431LIAIDBZR in SOT-23 package?

TL431LIAIDBZR in the SOT-23 (DBZ) package has a junction-to-ambient thermal resistance (RθJA) of 371.7°C/W. At maximum continuous cathode current (15 mA) and 36 V VKA, power dissipation reaches 0.54 W - raising junction temperature by ~200°C above ambient, exceeding the 150°C absolute max. Therefore, practical designs limit IKA×VKA to ≤300 mW. Derating is essential: at 85°C ambient, max allowable power is ~240 mW. Use PCB copper pour under the pad and minimize trace resistance to improve heat transfer. Thermal data is validated per JEDEC JESD51 standards and applies strictly to the DBZ package variant of TL431LIAIDBZR.