Texas Instruments TLV431AQPK

Overview

TLV431AQPK from Texas Instruments is a low-voltage adjustable precision shunt regulator in SOT-89-3 package, delivering 1.24V reference voltage with ±1.5% initial tolerance at 25°C, 11mV max VREF deviation over –40°C to 125°C, 0.25Ω typical dynamic impedance, and 55–100µA minimum cathode current for regulation - used in isolated flyback SMPS secondary-side feedback loops requiring stable 3.3V output regulation.

For engineers reviewing the TLV431AQPK datasheet, TLV431AQPK pinout, TLV431AQPK application, or TLV431AQPK equivalent, this page delivers verified electrical specs, thermal performance data, functional mode behavior (open-loop comparator vs closed-loop shunt regulator), real-world stability boundaries with capacitive loads, and precise selection guidance against comparable shunt references.

Technical Context

The TLV431AQPK operates as a 3-terminal adjustable shunt regulator with internal 1.24V bandgap reference and high-gain NPN-based error amplifier. Its Darlington output stage enables sharp turn-on and sink-current control down to 55µA cathode current, supporting both open-loop comparator operation (with integrated reference) and closed-loop voltage regulation via resistive feedback between cathode and reference pins.

Unlike the TL431, it achieves regulation starting at 1.24V cathode-anode voltage and maintains stability without external compensation capacitors - though Figure 5-19–5-21 define safe capacitive load limits (up to ~1nF at VKA = 5V) to preserve ≥45° phase margin across temperature.

Key Specifications

Pinout & Package

SOT-89-3 (PK) package: 4.5mm × 4.095mm footprint with gull-wing leads, thermally enhanced tab connected to ANODE for improved power dissipation in continuous 15mA operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV431BQPK, TLV431AQPK trades initial accuracy for cost efficiency in less demanding regulation tasks; versus TL431CDBZR, it enables lower-voltage operation, wider temperature range, and reduced bias current - making it the sole viable option for modern 3.3V isolated SMPS and automotive-grade voltage monitoring.

Availability

TLV431AQPK is available at Aetrix Electronics and suitable for isolated flyback power supplies, precision voltage monitoring circuits, programmable current sinks, and Zener-replacement applications requiring stable component supply across automotive, industrial, and telecom end equipment.

Supply support for TLV431AQPK 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 headquartered in Dallas, Texas, designing analog ICs, embedded processors, and power management solutions for industrial, automotive, and communications markets.

The TLV431x family was engineered specifically for low-voltage, low-power shunt regulation in space-constrained and thermally demanding applications - emphasizing precision, wide temperature operation, and compatibility with optocoupler-based isolation topologies.

FAQ

What is the maximum cathode-anode voltage (VKA) rating for TLV431AQPK?

The absolute maximum cathode-anode voltage for TLV431AQPK is 7V, per TI's SLVS139Z datasheet Section 5.1. Operating above this risks permanent damage. For reliable long-term use, the recommended maximum VKA is 6V - the upper limit of its adjustable output range - ensuring margin against transients and maintaining specified dynamic impedance and temperature drift performance.

Can TLV431AQPK replace a standard 3.3V Zener diode directly?

Yes, TLV431AQPK can directly replace a 3.3V Zener diode when configured with R1 = 16.2kΩ and R2 = 10kΩ (yielding VO ≈ 3.3V), but requires a minimum 55µA cathode current to regulate. Unlike a passive Zener, it draws negligible reference current (0.15–0.5µA), offers ±1.5% accuracy instead of ±5%, and maintains regulation down to 1.24V - making it superior for precision, low-power, or temperature-varying applications where Zener voltage drift exceeds 20mV.

Does TLV431AQPK require an output capacitor for stability?

No, TLV431AQPK is internally compensated and stable without an output capacitor between cathode and anode. However, if a capacitor is added (e.g., for noise filtering), TI's Figure 5-19–5-21 specifies safe limits: ≤0.47nF at VKA = 2.5V and ≤0.22nF at VKA = 5V to maintain ≥45° phase margin. Exceeding these values risks oscillation, especially at high temperatures.

What is the thermal resistance (RθJA) of TLV431AQPK in its SOT-89 package?

The junction-to-ambient thermal resistance (RθJA) for TLV431AQPK in the PK (SOT-89-3) package is 52°C/W, per Section 5.4 of the datasheet. This value assumes standard JEDEC 2-layer board conditions. With 15mA cathode current and 6V VKA, power dissipation reaches 90mW, resulting in ~4.7°C junction rise above ambient - well within the 125°C max operating temperature when ambient stays below 120°C.

How does the TLV431AQPK differ from TLV431AIPK in terms of temperature rating?

TLV431AQPK is characterized for operation from –40°C to 125°C (Q-grade), while TLV431AIPK is rated for –40°C to 85°C (I-grade). Both share identical electrical specs (1% VREF tolerance, same dynamic impedance, IK(min)), but TLV431AQPK undergoes extended temperature screening and is qualified for under-hood automotive applications, whereas TLV431AIPK targets industrial control cabinets or telecom power supplies with lower ambient thermal stress.