Texas Instruments TLVH431AQLP

Overview

TLVH431AQLP from Texas Instruments is a low-voltage adjustable precision shunt regulator in TO-92 package, functioning as a 1.24 V reference with ±1% initial tolerance at 25°C, 100 μA minimum cathode current for regulation, 0.25 Ω typical dynamic impedance, and operation across –40°C to +125°C. It replaces Zener diodes in secondary-side feedback of isolated 3.3 V flyback SMPSs.

For engineers reviewing the TLVH431AQLP datasheet, TLVH431AQLP pinout, TLVH431AQLP application, or TLVH431AQLP equivalent, key selection criteria include reference voltage accuracy over temperature, cathode current range (100 μA–70 mA), output impedance stability, thermal performance in TO-92, and compatibility with optocoupler-based isolated regulation circuits.

Technical Context

The TLVH431AQLP implements a precision bandgap reference and high-gain transconductance amplifier in a 3-terminal shunt topology. Its internal architecture forces the REF pin to 1.24 V when cathode current exceeds 100 μA and cathode-to-anode voltage is ≥1.24 V, enabling closed-loop regulation via external resistor dividers.

In open-loop mode, it operates as a comparator with integrated reference: REF voltage compared to internal 1.24 V threshold triggers sharp cathode current turn-on. The device is internally compensated and stable without output capacitance, though phase margin varies with capacitive load and cathode voltage per Figures 5-15–5-17.

Key Specifications

Pinout & Package

TLVH431AQLP uses a 3-pin TO-92 package (4.30 mm × 4.30 mm body size) with through-hole mounting. Pin 1 is CATHODE, Pin 2 is ANODE, Pin 3 is REF - matching Figure 4-3 in the datasheet. Anode serves as common ground reference; cathode sinks current to regulate voltage; REF senses feedback voltage.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLVH431BQLP, TLVH431AQLP trades 0.5% initial accuracy for cost savings while retaining identical temperature stability, cathode current range, and TO-92 footprint; versus TLVH432AQLP, it provides pin-compatible TO-92 implementation without layout revision but lacks the lower thermal resistance of SOT-89.

Availability

TLVH431AQLP is available at Aetrix Electronics and suitable for automotive power management, industrial sensor signal conditioning, and isolated DC-DC converter feedback requiring stable component supply across extended temperature ranges.

Supply support for TLVH431AQLP 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 ICs, with leadership in precision reference and power conversion technologies.

The TLVH431 family was designed for low-voltage, high-accuracy shunt regulation in isolated power supplies, data converters, and voltage monitoring - addressing limitations of legacy TL431 in sub-2.5 V systems.

FAQ

What is the reference voltage tolerance of TLVH431AQLP at 25°C?

The TLVH431AQLP has a reference voltage tolerance of ±1% at 25°C, corresponding to a V_REF range of 1.228 V to 1.252 V. This A-grade specification is confirmed in Section 5.6 of the datasheet and applies specifically to the TLVH431AQLP variant. The tolerance remains stable across its full operating temperature range of –40°C to +125°C, with total deviation capped at 31 mV for the Q-grade version.

Can TLVH431AQLP operate with cathode voltage below 2.5 V?

Yes, TLVH431AQLP is explicitly designed for low-voltage operation starting at 1.24 V cathode-to-anode voltage - significantly lower than the 2.5 V minimum required by TL431. This enables direct use in 1.8 V, 2.5 V, and 3.3 V systems. Operation at 1.24 V requires ≥100 μA cathode current and proper biasing of the REF pin; the device maintains regulation and specified dynamic impedance down to this minimum voltage.

What is the minimum cathode current required for regulation in TLVH431AQLP?

The TLVH431AQLP requires a minimum cathode current of 100 μA to enter and maintain regulation, as specified in Sections 5.5–5.7 of the datasheet. This value is guaranteed across the full –40°C to +125°C temperature range. Below this threshold, gain drops and regulation becomes unstable; above it, the device delivers precise 1.24 V reference behavior with 0.25 Ω dynamic impedance and sharp turn-on characteristics.

Is TLVH431AQLP stable without an output capacitor?

Yes, TLVH431AQLP is internally compensated and stable without an output capacitor between cathode and anode - a key differentiator from many linear regulators. This simplifies design in TO-92 layouts where capacitor placement is constrained. However, if external capacitance is added, Figures 5-15–5-17 in the datasheet provide phase margin guidance versus load capacitance and cathode voltage to avoid instability.

How does TLVH431AQLP differ from TLVH432AQLP in pin configuration?

TLVH431AQLP uses CATHODE/ANODE/REF pin order (1/2/3) in TO-92, while TLVH432AQLP uses REF/ANODE/CATHODE (1/2/3) - making them electrically identical but not pin-compatible. This difference is documented in Figures 4-3 and 4-7 of the datasheet. Substituting TLVH432AQLP requires PCB trace revision; TLVH431AQLP maintains direct compatibility with existing TO-92 footprints designed for the TLVH431 family.