Diodes Incorporated TL431BSA-7

Overview

TL431BSA-7 from Diodes Incorporated is a precision adjustable shunt regulator with 0.5% reference voltage tolerance (2.495 V ± 0.5%), 100 mA cathode sink current capability, and operation across –40°C to +125°C. It replaces Zener diodes in feedback loops of isolated DC-DC converters, voltage monitors, and programmable references where tight regulation and low output impedance (0.2 Ω typical) are required.

For engineers reviewing the TL431BSA-7 datasheet, TL431BSA-7 pinout, TL431BSA-7 application, or TL431BSA-7 equivalent, this page delivers verified electrical parameters, SOT23 package terminal mapping, real-world use cases in opto-coupler linearisation and overvoltage protection, and validated alternative parts with documented functional differences.

Technical Context

The TL431BSA-7 implements a bandgap-referenced error amplifier with internal 2.495 V reference, enabling precise voltage regulation via external resistor dividers. Its three-terminal architecture (Anode–Ref–Cathode) supports adjustable output from 2.5 V to 36 V while maintaining <34 mV reference deviation over –40°C to +125°C.

It operates as a two-quadrant shunt regulator: sinking 1–100 mA at the cathode while maintaining stable reference input current (1–4 µA typ.) and ultra-low dynamic output impedance (0.2 Ω). Stability is defined for load capacitances ≤50 pF, 5–20 nF, or >300 nF depending on cathode current.

Key Specifications

Pinout & Package

SOT23-3 package (JEDEC TO-236AB), 3.0 mm × 1.4 mm × 1.1 mm body, surface-mount, RoHS-compliant, halogen-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431BSA-7, TL431BIDBVR offers superior thermal handling in high-current operation but requires board rework, while AS431BT trades off reference accuracy and output impedance for lower unit cost-making TL431BSA-7 optimal for space-constrained, thermally limited, precision feedback designs.

Availability

TL431BSA-7 is available at Aetrix Electronics and suitable for isolated DC-DC converters, industrial voltage monitors, and programmable reference circuits requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for TL431BSA-7 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability power management, signal integrity, and protection solutions for industrial, computing, and automotive markets.

The TL431 product line delivers precision shunt regulation for feedback control in power supplies and voltage supervision, designed specifically to replace Zener diodes with improved accuracy, temperature stability, and sink current capability.

FAQ

What is the minimum cathode current required for regulation in TL431BSA-7?

The TL431BSA-7 requires a minimum cathode current of 0.4–0.7 mA to maintain regulation, as specified in the Electrical Characteristics table under IKA(MIN). This value is measured at V_KA = V_REF and ensures stable reference operation during light-load or standby conditions. Below this threshold, the device exits regulation and reference voltage becomes undefined.

Can TL431BSA-7 be used with ceramic output capacitors above 100 nF?

Yes, TL431BSA-7 is stable with ceramic output capacitors exceeding 300 nF when cathode current is below 5 mA, per the Stability Boundary Conditions chart. For higher currents, stability is guaranteed only with C_L ≤50 pF or between 5–20 nF. Using >100 nF outside these conditions risks oscillation unless verified with actual circuit testing.

How does the 0.5% reference tolerance impact feedback accuracy in a 12 V power supply?

In a 12 V output set by R1/R2 divider, the 0.5% V_REF tolerance contributes ±0.0125 V absolute error at the reference node. With typical resistor tolerances (1%), total output error remains within ±1.2%, significantly tighter than standard Zener-based solutions (±5–10%). This directly enables compliance with industrial 12 V ±5% specifications without calibration.

Is TL431BSA-7 pin-compatible with legacy TL431A variants in SOT23?

Yes, TL431BSA-7 uses the standard SOT23-3 pinout (Anode–Ref–Cathode) identical to TL431ASA-7 and all Diodes TL431xSA variants. No PCB layout change is required when upgrading from A-grade to B-grade; only the marking code changes from "AA" to "AB", and the reference tolerance improves from ±1.0% to ±0.5%.