Diodes Incorporated TL431ASA-7

Overview

TL431ASA-7 from Diodes Incorporated is a three-terminal adjustable precision shunt regulator with 1% initial reference voltage tolerance (2.495 V ±1.0%), 100 mA sink current capability, and operation across –40°C to +125°C. It replaces discrete Zener diodes in feedback loops of isolated DC-DC converters, voltage monitors, and optocoupler-based regulation circuits where stable 2.5–36 V programmable references are required.

For engineers reviewing the TL431ASA-7 datasheet, TL431ASA-7 pinout, TL431ASA-7 application, or TL431ASA-7 equivalent, key selection criteria include reference voltage accuracy over temperature, dynamic output impedance (0.2 Ω typ), cathode current range (1–100 mA), and SOT23 package thermal resistance (380°C/W).

Technical Context

The TL431ASA-7 implements an internal bandgap reference and transconductance amplifier driving an NPN output stage, enabling precise voltage regulation via external resistor dividers. Its reference input (REF) senses a fraction of cathode-to-anode voltage, and the device adjusts cathode current to maintain V_REF = 2.495 V at the REF pin.

It operates as a two-quadrant shunt regulator: sinking current when V_KA > V_REF(1 + R1/R2), and entering high-impedance off-state (I_KOFF ≤ 0.5 µA) when V_KA < V_REF. Stability is conditional on load capacitance-stable with ≤50 pF, 5–20 nF, or >300 nF, but not mid-range values without series resistance.

Key Specifications

Pinout & Package

TL431ASA-7 is housed in a RoHS-compliant SOT23-3 surface-mount package (3.0 × 1.4 × 1.1 mm), optimized for low-cost, high-density PCB layouts and automated assembly. Thermal resistance is 380°C/W (junction-to-ambient), requiring attention to copper pour and airflow in >50 mA applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431CDBVR and AS431ASTZ, TL431ASA-7 offers the best balance of accuracy (±1%), compact SOT23 footprint, and thermal performance for space-constrained industrial power supplies requiring stable 2.5–36 V references.

Availability

TL431ASA-7 is available at Aetrix Electronics and suitable for isolated DC-DC converters, overvoltage protection circuits, and programmable voltage monitors requiring stable component supply with guaranteed long-term manufacturability.

Supply support for TL431ASA-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 power management, signal integrity, and protection solutions for industrial, computing, and consumer markets.

TL431ASA-7 belongs to Diodes' precision reference product line, engineered for high-accuracy voltage regulation in feedback control loops where Zener diode limitations-poor tempco, high impedance, and inconsistent tolerances-must be overcome.

FAQ

What is the minimum cathode current required for regulation?

The TL431ASA-7 requires a minimum cathode current of 0.4 mA (typical) to maintain regulation. Below this threshold, the device exits active regulation and enters high-impedance state, causing output voltage to rise uncontrolled. Designers must ensure external circuitry provides ≥0.7 mA (max spec) under all operating conditions, often using a bleed resistor from cathode to input rail.

Can TL431ASA-7 replace a standard Zener diode directly?

Yes-TL431ASA-7 can directly replace Zener diodes rated 2.5–36 V in shunt regulator configurations, but requires two external resistors to set the output voltage. Unlike Zeners, it delivers superior temperature stability (±34 mV over –40°C to +125°C), lower dynamic impedance (0.2 Ω), and tighter initial tolerance (±1%), making it ideal for precision feedback paths.

How does load capacitance affect TL431ASA-7 stability?

TL431ASA-7 exhibits conditional stability: it is stable with load capacitance ≤50 pF, 5–20 nF, or >300 nF, but may oscillate at mid-range values (e.g., 100–200 nF). For flyback converters, use ≤50 pF or add a 30 Ω series resistor with 100 nF to dampen ringing. Always verify phase margin with network analyzer or transient simulation.

What is the maximum power dissipation in SOT23 package?

In SOT23, TL431ASA-7 has a maximum power dissipation of 330 mW at 25°C ambient. At 100 mA cathode current and 10 V cathode-anode differential, power dissipation reaches 1 W-exceeding the package limit. Derating is required: at 85°C ambient, max dissipation drops to ~180 mW. Use thermal vias and copper pour to extend usable current range.