Texas Instruments TL431CDBZT

Overview

TL431CDBZT from Texas Instruments is a precision programmable shunt voltage reference in SOT-23-3 package, delivering 2.495 V nominal reference voltage with ±0.5% initial tolerance (B-grade), 0.2 Ω typical dynamic impedance, and operation from 0°C to 70°C. It replaces Zener diodes in adjustable power supplies, isolated feedback loops, and voltage monitoring circuits for rack server power and notebook PC adapters.

For engineers reviewing the TL431CDBZT datasheet, TL431CDBZT pinout, TL431CDBZT application, or TL431CDBZT equivalent, this page provides verified electrical specs, thermal behavior, stability boundaries, noise performance, and real-world implementation guidance for closed-loop regulation design.

Technical Context

The TL431CDBZT implements an internal error amplifier with high-gain transconductance stage driving a NPN output transistor, enabling sharp turn-on and precise threshold detection at the REF pin relative to ANODE. Its three-terminal architecture supports adjustable output from 2.495 V to 36 V using two external resistors without requiring external biasing.

It operates as a shunt regulator: cathode current (IKA) sinks 1–100 mA while maintaining stable VKA across load and line variations; reference input current (Iref) remains ultra-low (2–4 µA), minimizing divider network loading and enabling high-impedance sensing.

Key Specifications

Pinout & Package

SOT-23-3 package (2.90 mm × 1.30 mm), surface-mount, lead-free, RoHS-compliant. Pin 1 = REF (input reference threshold), Pin 2 = CATHODE (shunt current sink/output), Pin 3 = ANODE (common return/reference ground).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431IDBZT and TLVH431IDBZR, TL431CDBZT offers the tightest initial accuracy (±0.5%) within its 0°C–70°C range, making it optimal for cost-sensitive commercial power supplies where thermal derating is not required and regulation precision is critical.

Availability

TL431CDBZT is available at Aetrix Electronics and suitable for rack server power, notebook PC power adapter design, and industrial AC/DC applications requiring stable component supply, consistent parametric performance, and long-term manufacturing continuity.

Supply support for TL431CDBZT 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 specializing in analog, embedded processing, and power management ICs, with decades of expertise in precision reference design and high-volume manufacturing.

The TL431 product line was engineered for universal shunt reference replacement in switching power supplies, offering programmable voltage, low drift, and robust stability - targeting cost-effective, high-reliability power conversion across computing, industrial, and consumer markets.

FAQ

What is the reference voltage tolerance of TL431CDBZT at 25°C?

The TL431CDBZT has a reference voltage tolerance of ±0.5% at 25°C (B-grade specification), corresponding to a 2.483 V to 2.507 V range. This tight tolerance is confirmed in Section 6.11 of the TI SLVS543S datasheet and applies specifically to the TL431CDBZT variant in SOT-23-3 packaging. The TL431CDBZT achieves this accuracy without calibration, supporting high-precision feedback in commercial-grade power supplies.

Can TL431CDBZT replace a Zener diode in a 12 V regulator circuit?

Yes, TL431CDBZT can directly replace a Zener diode in a 12 V regulator circuit by configuring R1 and R2 to set VOUT = 2.495 × (1 + R1/R2). For 12 V output, use R1 = 380 kΩ and R2 = 100 kΩ (standard values). Unlike Zeners, TL431CDBZT provides sharper knee characteristics, lower dynamic impedance (0.2 Ω vs. ~10 Ω for Zener), and stable performance across temperature - all verified in TI's application note SNVA202.

What is the maximum cathode voltage rating for TL431CDBZT?

The absolute maximum cathode voltage (VKA) for TL431CDBZT is 37 V, with recommended operating range from Vref (2.495 V) to 36 V. Exceeding 37 V risks permanent damage per Section 6.1 of the SLVS543S datasheet. This rating is independent of package and applies identically to all TL431C variants, including TL431CDBZT.

Does TL431CDBZT require an external capacitor for stability?

TL431CDBZT does not require an external capacitor for basic operation, but stability depends on load capacitance and cathode current. Figure 6-16 in the datasheet defines oscillation boundaries: for VKA = 5 V, instability occurs above ~10 mA with >100 nF CL. A 1 nF ceramic capacitor from cathode to anode is commonly used in flyback feedback designs to ensure phase margin >45°, as validated in TI reference design PMP22392.

How does the temperature coefficient of TL431CDBZT compare to TL431IDBZT?

TL431CDBZT exhibits ≤6 mV total deviation over 0°C–70°C (C-temp grade), while TL431IDBZT shows ≤14 mV over –40°C–85°C (I-temp grade). Both share identical bandgap architecture, but the wider range of TL431IDBZT inherently increases worst-case drift. The TL431CDBZT's tighter spec reflects optimization for commercial ambient conditions, making it preferable where thermal range is constrained and accuracy is prioritized.