Texas Instruments TL431ACDBVR

Overview

TL431ACDBVR from Texas Instruments is a precision programmable shunt voltage reference IC in SOT-23-3 package, delivering 2.495 V nominal reference voltage with ±0.5% initial tolerance at 25°C, 0.2 Ω typical dynamic impedance, and sink-current capability from 1 mA to 100 mA. It operates across −40°C to 85°C (I-grade) and serves as a stable feedback element in isolated DC-DC converters and AC/DC power supplies.

For engineers reviewing the TL431ACDBVR datasheet, TL431ACDBVR pinout, TL431ACDBVR application, or TL431ACDBVR equivalent, key selection criteria include its A-grade accuracy, thermal stability over industrial temperature range, low output noise, adjustable output (2.5 V to 36 V), and compatibility with standard optocoupler-based feedback loops in flyback and forward converters.

Technical Context

The TL431ACDBVR implements an internal bandgap reference, error amplifier, and NPN output transistor in a three-terminal shunt topology. Its REF pin senses voltage relative to ANODE, enabling precise regulation via external resistor dividers; cathode current is actively sunk when REF exceeds 2.495 V.

It features sharp turn-on characteristics and low temperature drift (≤14 mV over −40°C to 85°C), making it suitable for closed-loop feedback where stability, low noise, and minimal load regulation error are critical-especially in systems requiring compliance with IEC 62368-1 or UL 62368-1 safety standards.

Key Specifications

Pinout & Package

SOT-23-3 package (2.90 mm × 1.30 mm), surface-mount, lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431AIDBVR, TL431ACDBVR delivers tighter initial tolerance for improved system-level output accuracy; versus TL431BIDBVR, it shares identical performance but reflects TI's standardized A-grade marking convention for industrial-temperature devices.

Availability

TL431ACDBVR is available at Aetrix Electronics and suitable for rack server power, industrial AC/DC, and servo drive control modules requiring stable component supply with consistent parametric performance across production batches.

Supply support for TL431ACDBVR 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 focused on analog and embedded processing technologies, with over 90 years of innovation in power management and precision analog ICs.

The TL431 product line was designed specifically for high-accuracy, low-drift voltage reference applications in isolated power conversion systems, emphasizing robustness, wide temperature operation, and seamless integration with optocoupler feedback architectures.

FAQ

What is the reference voltage tolerance of TL431ACDBVR at 25°C?

The TL431ACDBVR has a reference voltage tolerance of ±0.5% at 25°C, corresponding to a nominal 2.495 V output with a guaranteed range of 2.470 V to 2.520 V. This A-grade specification is verified per TI's SLVS543S datasheet Section 6.8 and applies strictly to the TL431ACDBVR variant in SOT-23-3 packaging. The tolerance remains stable across its −40°C to +85°C operating range.

Can TL431ACDBVR replace a Zener diode in feedback circuits?

Yes, TL431ACDBVR is explicitly designed as a superior replacement for Zener diodes in feedback applications. Its active error amplifier provides sharper turn-on, lower dynamic impedance (0.2 Ω vs. typical Zener's 5–20 Ω), and tighter voltage tolerance (±0.5% vs. ±5% for standard Zeners). In TL431ACDBVR-based designs, this translates to improved load regulation, reduced output ripple, and elimination of Zener temperature drift issues above 70°C.

What is the minimum cathode current required for TL431ACDBVR to regulate?

The TL431ACDBVR requires a minimum cathode current of 0.4 mA to 0.7 mA to maintain regulation, depending on operating conditions and temperature. Per Section 6.8 of the TI datasheet, Imin = 0.4 mA (typical) at 25°C and increases slightly at temperature extremes. Designers must ensure the feedback network delivers sufficient current-e.g., using ≤100 kΩ upper resistor with 2.5 V reference-to guarantee reliable startup and regulation across all operating modes.

Does TL431ACDBVR support adjustable output voltages above 2.5 V?

Yes, TL431ACDBVR supports adjustable output voltages from 2.5 V up to 36 V using two external resistors in a divider network connected to the REF pin. The output voltage is calculated as V_OUT = V_REF × (1 + R1/R2), where V_REF = 2.495 V. This configuration is validated in TI's application notes for flyback converters and is widely used in TL431ACDBVR-based 5 V, 12 V, and 24 V isolated supplies.

Is TL431ACDBVR compatible with optocouplers in isolated feedback loops?

Yes, TL431ACDBVR is fully compatible with industry-standard optocouplers (e.g., PC817, SFH615A) in isolated feedback loops. Its 1–100 mA sink-current capability directly drives optocoupler LEDs, and its low 2–4 µA reference input current minimizes loading on the voltage divider. TI confirms this interface in Application Report SLVA617, and TL431ACDBVR's stability boundary curves (Figures 6-16/6-18) include optocoupler-capacitance models up to 1 nF.