Texas Instruments TLV431ILP

Overview

TLV431ILP from Texas Instruments is a low-voltage adjustable precision shunt regulator in TO-92 (LP) package, delivering 1.24 V reference voltage with ±1.5% initial tolerance at 25°C, 0.25 Ω typical dynamic impedance, and operation down to 1.24 V cathode-anode voltage. It serves as a Zener diode replacement or error amplifier in isolated flyback SMPS feedback loops requiring stable 3.3 V output regulation.

For engineers reviewing the TLV431ILP datasheet, TLV431ILP pinout, TLV431ILP application, or TLV431ILP equivalent, key selection criteria include reference voltage accuracy over temperature (±11 mV from –40°C to 125°C), minimum cathode current (80 µA typical), ultra-low reference terminal current (0.5 µA max), and TO-92 thermal performance (R_θJA = 140°C/W).

Technical Context

The TLV431ILP implements a bandgap-based reference with internal NPN Darlington output stage, enabling sharp turn-on and stable closed-loop regulation when configured with external resistive feedback between cathode and reference pins. Its open-loop mode supports comparator functionality with integrated 1.24 V threshold.

It operates across –40°C to 85°C (I-grade), requires ≥1.24 V cathode-anode headroom, and maintains regulation with cathode current from 80 µA to 15 mA - making it suitable for low-power secondary-side sensing where TL431 cannot operate due to higher 2.5 V reference and 1 mA minimum cathode current.

Key Specifications

Pinout & Package

TLV431ILP uses the LP (TO-92/TO-226) 3-pin through-hole package (5.2 mm × 3.68 mm), optimized for manual assembly and legacy board designs. Pin 1 is ANODE (common ground connection), Pin 2 is CATHODE (shunt current input/output), and Pin 3 is REF (reference input node).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV431ILP, TLV431ACLPR offers improved initial accuracy at no layout change, while TLV431BILP delivers highest precision in the same TO-92 form factor - both retain identical thermal behavior (R_θJA = 140°C/W) and cathode current requirements.

Availability

TLV431ILP is available at Aetrix Electronics and suitable for industrial power supplies, battery management systems, and legacy through-hole instrumentation requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for TLV431ILP 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 leader designing analog ICs, embedded processors, and connectivity solutions for industrial, automotive, and communications markets.

The TLV431 family was developed specifically for low-voltage shunt regulation and precision voltage monitoring in space-constrained, energy-efficient power systems - extending the utility of the classic TL431 architecture to modern 3.3 V and lower domains.

FAQ

What is the maximum cathode voltage rating for TLV431ILP?

The absolute maximum cathode-to-anode voltage (V_KA) for TLV431ILP is 7 V. This rating applies across the full operating temperature range and defines the upper limit for safe operation - exceeding this voltage risks permanent damage. In normal use, TLV431ILP regulates up to 6 V output, leaving 1 V margin for transient spikes and ripple. Always ensure the cathode voltage remains within 1.24 V to 6 V during regulation and does not exceed 7 V under any condition.

Does TLV431ILP require an external capacitor for stability?

No, TLV431ILP is internally compensated and remains stable without an external output capacitor between cathode and anode in standard configurations. This eliminates a common BOM item and simplifies layout. However, if a capacitive load is added - such as an optocoupler LED with parasitic capacitance - stability must be verified using TI's phase margin vs. capacitive load curves (Figures 5-19 to 5-21). For marginal cases, a small ceramic capacitor (e.g., 100 pF) may be added in parallel with the feedback resistor.

Can TLV431ILP be used as a comparator, and what are its response limitations?

Yes, TLV431ILP functions as a comparator with integrated 1.24 V reference in open-loop mode. Its response speed depends on cathode current and overdrive: ≥500 µA cathode current and ≥10% overdrive (e.g., 1.36 V at REF for 1.24 V nominal) yield fast transitions. Below 80 µA cathode current, gain drops significantly, causing slow or incomplete switching. The output swings from ~1 V (low) to V_CC (high, open-collector), requiring pull-up for logic-level compatibility.

What is the thermal resistance of TLV431ILP in its TO-92 package?

TLV431ILP in the LP (TO-92) package has a junction-to-ambient thermal resistance (R_θJA) of 140°C/W under standard JEDEC test conditions. This value assumes no copper pour or heatsinking; adding 1 in² of 2-oz copper on the ANODE pad reduces R_θJA by ~20°C/W. At 15 mA cathode current and 5 V V_KA, power dissipation is ~75 mW, resulting in ~10.5°C rise above ambient - well within the –40°C to 85°C operating range.

How does the reference terminal current (I_ref) affect feedback resistor selection in TLV431ILP circuits?

TLV431ILP draws up to 0.5 µA into the REF pin, which flows through the lower feedback resistor (R2) in standard divider configurations. To limit voltage error to <0.1%, R2 should be ≤100 kΩ (0.5 µA × 100 kΩ = 50 mV drop at 1.24 V reference). Higher values increase error and temperature sensitivity. For precision applications, use R2 = 10 kΩ–47 kΩ and calculate R1 accordingly: R1 = R2 × ((V_OUT/1.24) – 1). Always verify total divider current exceeds 80 µA minimum cathode requirement.