Texas Instruments TLVH431BQDBZT

Overview

TLVH431BQDBZT from Texas Instruments is a low-voltage adjustable precision shunt regulator in SOT-23-3 package, functioning as a 1.24 V reference with 0.5% initial tolerance at 25°C, 100 μA minimum cathode current for regulation, and operation from –40°C to +125°C. It replaces Zener diodes in secondary-side feedback of isolated 3.3 V flyback SMPSs and serves as an integrated-reference comparator.

For engineers reviewing the TLVH431BQDBZT datasheet, TLVH431BQDBZT pinout, TLVH431BQDBZT application, or TLVH431BQDBZT equivalent, key selection criteria include reference voltage accuracy over temperature, cathode current range (100 μA–70 mA), dynamic impedance (0.25 Ω), thermal stability (±31 mV over –40°C to +125°C), and SOT-23-3 pin compatibility with TLVH432 variants.

Technical Context

The TLVH431BQDBZT implements a bandgap-referenced error amplifier with Darlington output stage, enabling precise shunt regulation via external resistor divider between cathode and reference pins. Its internal 1.24 V reference is stable across –40°C to +125°C with typical temperature coefficient of ±25 ppm/°C (derived from ±31 mV deviation over 165°C range).

It operates in two functional modes: open-loop comparator (with integrated 1.24 V threshold) and closed-loop shunt regulator (with feedback establishing VO = VREF × (1 + R1/R2)). No external compensation capacitor is required due to internal frequency compensation, though stability with capacitive loads is characterized up to 10 nF.

Key Specifications

Pinout & Package

SOT-23-3 package (2.92 mm × 1.30 mm body size) with gull-wing leads; thermally enhanced for 206°C/W junction-to-ambient resistance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLVH431BQDBZT, TLVH431BQDBVT offers identical regulation performance but demands PCB rework for its 5-pin layout, while TLVH432BQDBZT provides identical functionality with inverted pinout-neither is a direct replacement without hardware changes, making TLVH431BQDBZT optimal for new designs prioritizing compact SOT-23-3 integration and proven flyback feedback layouts.

Availability

TLVH431BQDBZT is available at Aetrix Electronics and suitable for isolated SMPS feedback, precision voltage monitoring, and low-power shunt regulation requiring stable component supply across automotive, industrial control, and telecom infrastructure programs.

Supply support for TLVH431BQDBZT 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 delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, longevity, and industrial-grade qualification.

The TLVH431 product line was designed specifically for precision shunt regulation in low-voltage, high-stability applications-including isolated power supplies, data converter references, and intelligent power monitoring-where legacy TL431 devices cannot operate below 2.5 V.

FAQ

What is the reference voltage tolerance of TLVH431BQDBZT at 25°C?

The TLVH431BQDBZT has a reference voltage tolerance of ±0.5% at 25°C, corresponding to a 1.24 V nominal V_REF with min/max values of 1.234 V and 1.246 V. This B-grade accuracy is confirmed in Section 5.7 of the TI SLVS555N datasheet and applies across the full SOT-23-3 packaged variant. The TLVH431BQDBZT maintains this specification under recommended operating conditions with 10 mA cathode current.

Can TLVH431BQDBZT replace a standard Zener diode in low-leakage applications?

Yes, TLVH431BQDBZT replaces Zener diodes effectively due to its 0.02–0.1 μA off-state cathode current (IK(off)), which is orders of magnitude lower than typical Zener leakage. Its sharp turn-on characteristic, 0.25 Ω dynamic impedance, and 1.24 V reference enable superior regulation accuracy and thermal stability. Unlike Zeners, TLVH431BQDBZT requires only 100 μA minimum cathode current to regulate, reducing bias power significantly in always-on monitoring circuits.

What is the minimum cathode current required for regulation in TLVH431BQDBZT?

The TLVH431BQDBZT requires a minimum cathode current (I_K(min)) of 100 μA to maintain regulation, as specified in Sections 5.5–5.7 of the datasheet. This value is valid across the full temperature range (–40°C to +125°C) and is critical for ensuring sufficient gain in the internal Darlington stage. Operating below 100 μA risks degraded regulation accuracy and increased output impedance, especially at temperature extremes.

How does TLVH431BQDBZT differ from TLVH432BQDBZT in pin configuration?

TLVH431BQDBZT uses Pin 1=CATHODE, Pin 2=REF, Pin 3=ANODE in SOT-23-3, whereas TLVH432BQDBZT uses Pin 1=REF, Pin 2=CATHODE, Pin 3=ANODE. This reversal means they are not pin-compatible: substituting TLVH432BQDBZT for TLVH431BQDBZT without PCB modification will misconnect REF and CATHODE, causing regulation failure. Both share identical electrical specs, but pinout difference mandates schematic and layout verification.

Is an output capacitor required for stability with TLVH431BQDBZT?

No, TLVH431BQDBZT is internally compensated and stable without an output capacitor between CATHODE and ANODE. This eliminates BOM cost and layout complexity in most applications. However, if a capacitive load is present (e.g., long traces or EMI filtering), Figures 5-15–5-17 in the datasheet provide phase-margin guidance up to 10 nF; stability margins remain acceptable within recommended operating conditions without added capacitance.