Diodes Incorporated ZTL431AFTA

Overview

ZTL431AFTA from Diodes Incorporated is a three-terminal adjustable precision shunt regulator in SOT23 package, providing 2.5V reference voltage with ±1% initial tolerance at +25°C, 0.2Ω typical dynamic output impedance, and 1mA–100mA sink current capability. It operates across –40°C to +125°C and replaces zener diodes in feedback loops of linear regulators, opto-coupler-based isolated power supplies, and overvoltage protection circuits.

For engineers reviewing the ZTL431AFTA datasheet, ZTL431AFTA pinout, ZTL431AFTA application, or ZTL431AFTA equivalent, this device is selected for high-temperature-stable voltage reference design, programmable threshold generation, and low-impedance shunt regulation where tight VREF accuracy and minimal thermal drift are required.

Technical Context

The ZTL431AFTA implements a bandgap-referenced error amplifier driving an NPN output stage, enabling precise regulation via external resistor divider between cathode and reference pins. Its internal architecture delivers stable operation up to 20V cathode-anode voltage and supports capacitive loads ≥4.7nF for guaranteed stability.

It features a reference input current of 2–4μA (typ), <0.5μA off-state leakage at 20V, and a temperature coefficient of ≤34mV deviation over –40°C to +125°C - meeting industrial-grade requirements without external compensation.

Key Specifications

Pinout & Package

Package: SOT23 (JEDEC TO-236AB), 3-pin surface-mount, 2.9mm × 1.3mm footprint, 1.1mm max height. Thermal resistance θ_JA = 380°C/W; P_DIS = 330mW at T_A = +25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431ACDBVR, ZTL431AFTA offers lower max voltage but superior thermal stability over –40°C to +125°C; versus ZTL432AFTA, it provides identical performance with standard TL431-compatible pinout - critical for minimizing layout changes in existing designs.

Availability

ZTL431AFTA is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, and isolated DC-DC converters requiring stable component supply, extended temperature operation, and RoHS-compliant sourcing.

Supply support for ZTL431AFTA 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, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

ZTL431 belongs to Diodes' precision reference product line, engineered for cost-effective, high-stability shunt regulation in space-constrained industrial and automotive applications where reliability across extended temperature ranges is mandatory.

FAQ

What is the minimum cathode current required for regulation in ZTL431AFTA?

The ZTL431AFTA requires a minimum cathode current of 0.4mA to 0.6mA (typ/max) to maintain regulation. Below this threshold, the device exits active regulation mode and VREF becomes undefined. This value is specified at V_KA = V_REF and ensures reliable startup and light-load stability in feedback circuits.

Can ZTL431AFTA replace a standard 2.5V zener diode directly?

Yes - ZTL431AFTA can directly replace a 2.5V zener diode in most applications, offering superior parameters: ±1% initial tolerance (vs. ±5% for typical zeners), 0.2Ω dynamic impedance (vs. 10–100Ω), and stable operation from –40°C to +125°C. No circuit modification is needed beyond connecting Ref to the zener cathode node and Anode to ground.

Is external compensation required for stability with capacitive loads?

A 4.7nF or larger capacitor between anode and cathode is recommended to ensure stability across all operating conditions. The ZTL431AFTA exhibits a known instability zone with small capacitive loads (<1nF); adding this capacitor eliminates oscillation risk without requiring additional resistors or complex network design.

How does ZTL431AFTA differ from ZTL432AFTA electrically and physically?

Electrically, ZTL431AFTA and ZTL432AFTA are identical in all specifications including VREF, I_KA, R_Z, and temperature range. Physically, they differ only in pinout: ZTL431AFTA uses Anode–Cathode–Ref (1–2–3), while ZTL432AFTA uses Cathode–Anode–Ref (1–2–3) in SOT23. PCB layout must be revised for pin swap.