Texas Instruments TLV431BQLP

Overview

TLV431BQLP from Texas Instruments is a low-voltage adjustable precision shunt regulator with 1.24 V reference voltage, 0.5% initial tolerance at 25°C, and operation from 1.24 V to 6 V output range. It delivers 0.25 Ω typical dynamic impedance, 80 µA typical cathode current, and supports secondary-side regulation in isolated flyback SMPSs.

For engineers reviewing the TLV431BQLP datasheet, TLV431BQLP pinout, TLV431BQLP application, or TLV431BQLP equivalent, key selection considerations include reference accuracy over temperature (±11 mV from –40°C to 125°C), ultra-small TO-92 package footprint (5.2 mm × 3.68 mm), cathode current requirements for regulation (55–100 µA), and compatibility with optocoupler-based feedback loops in 3.3 V systems.

Technical Context

The TLV431BQLP implements a precision bandgap reference and high-gain NPN-based error amplifier in a 3-terminal shunt topology. Its internal architecture enables closed-loop voltage regulation via resistive feedback between cathode and reference pins, or open-loop comparator operation with integrated 1.24 V threshold.

It operates with ≥1.24 V cathode-to-anode voltage and requires ≥55 µA cathode current to maintain regulation across –40°C to 125°C (Q-grade). The device is internally compensated and stable without external capacitors, though phase margin vs. capacitive load is characterized up to 1 nF.

Key Specifications

Pinout & Package

TLV431BQLP uses the LP (TO-92/TO-226) package: 3-pin through-hole, 5.2 mm × 3.68 mm body, lead pitch 1.27 mm, anode pin centered.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV431BIDBZR, TLV431BQLP offers mechanical robustness and hand-solderability but larger board area; compared with TLVH431BQDBVR, it trades voltage range and current capability for lower cost, smaller die size, and direct compatibility with legacy TO-92 footprints.

Availability

TLV431BQLP is available at Aetrix Electronics and suitable for industrial power supplies, automotive body electronics, and medical instrumentation requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for TLV431BQLP 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, embedded processing, and power management technologies, with decades of leadership in precision references and power ICs.

The TLV431 family was designed specifically for low-voltage, high-accuracy shunt regulation in space- and power-constrained applications including isolated DC/DC converters, voltage supervisors, and analog signal conditioning.

FAQ

What is the maximum cathode voltage rating for TLV431BQLP?

The absolute maximum cathode-to-anode voltage (V_KA) for TLV431BQLP is 7 V. Operation beyond this risks permanent damage. For reliable regulation, the recommended operating range is 1.24 V to 6 V, aligning with its adjustable output specification. This limit is defined in Section 5.1 of the SLVS139Z datasheet and applies across all temperature grades including the Q-grade (–40°C to 125°C) used in TLV431BQLP.

Does TLV431BQLP require an external capacitor for stability?

No, TLV431BQLP is internally compensated and stable without an external output capacitor between cathode and anode. This is confirmed in Section 7.3 of the datasheet. However, if a capacitive load is added (e.g., for noise filtering), Figure 5-19–5-21 provide phase margin vs. capacitive load data up to 1 nF to guide selection and avoid oscillation in specific layouts.

How does the TO-92 package of TLV431BQLP affect thermal performance?

The LP (TO-92) package has a junction-to-ambient thermal resistance (R_θJA) of 140°C/W, per Section 5.4. This is higher than SOT-23 variants (e.g., 206°C/W for DBZ) but lower than SOIC-8 (97°C/W). In practice, TLV431BQLP remains thermally viable for ≤15 mA cathode current in still-air environments; derating is advised above 85°C ambient.

Can TLV431BQLP replace a standard 3.3 V Zener diode?

Yes - TLV431BQLP can directly replace a 3.3 V Zener in shunt regulator or voltage-reference roles. Set R1 and R2 such that V_OUT = 1.24 V × (1 + R1/R2). Its 0.5% initial tolerance, ±11 mV tempco, and 0.25 Ω impedance deliver significantly better accuracy and regulation than typical 5% Zeners with >50 mV/°C drift.

What is the minimum cathode current needed for regulation in TLV431BQLP?

TLV431BQLP requires a minimum cathode current (I_K(min)) of 55 µA (typical) to 100 µA (maximum) to maintain regulation across –40°C to 125°C, per Section 5.7. Below this, gain drops and regulation degrades. This value is lower than TL431's 1 mA requirement, enabling use in ultra-low-power standby modes where TLV431BQLP excels.