Diodes Incorporated ZTLV431AFTA

Overview

ZTLV431AFTA from Zetex Semiconductors is a precision 1.24 V adjustable shunt voltage reference in SOT23 package, functioning as a three-terminal programmable shunt regulator with ±1% initial tolerance, -40°C to +125°C operating range, and 0.25 Ω typical dynamic output impedance. It replaces standard Zener diodes in feedback loops of isolated DC-DC converters, linear regulators, and optocoupler-based feedback circuits requiring stable low-voltage reference.

For engineers reviewing the ZTLV431AFTA datasheet, ZTLV431AFTA pinout, ZTLV431AFTA application, or ZTLV431AFTA equivalent, key selection criteria include its 1.24 V reference voltage, 100 µA minimum cathode current for regulation, 20 mA max cathode current capability, temperature drift of 11 mV over -40°C to +125°C, and SOT23 footprint compatibility with space-constrained power management designs.

Technical Context

The ZTLV431AFTA operates as a two-input, one-output shunt regulator: the reference input (REF) senses voltage across an external resistor divider, while cathode (K) sinks current to maintain V_REF = 1.24 V at the REF pin. Regulation occurs only when cathode voltage exceeds V_REF and cathode current remains ≥100 µA.

Its internal bandgap-derived reference provides stable 1.24 V output with 4 mV drift over 0°C–70°C and 11 mV over full -40°C–125°C range. Dynamic output impedance is 0.25 Ω at 1 kHz, enabling fast transient response in closed-loop feedback systems where low-impedance reference stability is critical.

Key Specifications

Pinout & Package

SOT23-3 package (JEDEC TO-236AB), 3-pin surface-mount device with 1.9 mm pitch, 2.8 mm × 2.6 mm footprint, and 1.12 mm height. Thermal resistance θ_JA = 380°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLVH431AIDBVR and AS431ARTDT, ZTLV431AFTA offers optimal balance of low 1.24 V reference, ±1% tolerance, and 0.25 Ω impedance-making it preferred for high-accuracy isolated DC-DC feedback where headroom is limited and thermal stability is critical.

Availability

ZTLV431AFTA is available at Aetrix Electronics and suitable for isolated flyback converters, optocoupler-based feedback networks, and low-voltage LDO reference circuits requiring stable component supply across automotive, industrial, and telecom power designs.

Supply support for ZTLV431AFTA 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

Zetex Semiconductors (now part of Diodes Incorporated) is a UK-based ISO 9001/TS16949-certified designer of high-performance analog and power semiconductors, specializing in precision references, drivers, and protection devices.

The ZTLV431 series was developed specifically for high-reliability shunt regulation in space-constrained, wide-temperature power management systems-emphasizing low-voltage operation, tight tolerance, and robust thermal performance.

FAQ

What is the minimum cathode current required for ZTLV431AFTA to regulate?

The ZTLV431AFTA requires a minimum cathode current of 100 µA to maintain regulation across its full -40°C to +125°C operating range. Below this threshold, the device exits regulation and reference voltage collapses. This value is confirmed in the Electrical Characteristics table under IKMIN at TA = -40 to 125°C, with typical performance at 55 µA but guaranteed minimum of 100 µA.

Can ZTLV431AFTA replace a standard 3.3 V Zener diode directly?

No-ZTLV431AFTA cannot directly replace a 3.3 V Zener because its reference voltage is fixed at 1.24 V. To achieve 3.3 V output, it must be used with two external resistors (R1, R2) in a voltage divider configuration per Figure 2 of the datasheet. The output voltage is calculated as V_OUT = V_REF × (1 + R1/R2), enabling programmable outputs from 1.24 V to 10 V.

What is the maximum power dissipation of ZTLV431AFTA in SOT23 package?

The ZTLV431AFTA in SOT23 has a maximum power dissipation of 330 mW at TA = 25°C, based on its thermal resistance θ_JA = 380°C/W and absolute maximum junction temperature of 150°C. Derating begins above 25°C at 0.87 mW/°C, reaching zero dissipation at 125°C ambient per the Power Dissipation vs Ambient Temperature curve on page 4 of the datasheet.

Does ZTLV431AFTA require an output capacitor for stability?

Stability depends on circuit configuration: no capacitor is required for basic shunt operation, but capacitive loading >1 nF on the cathode can cause oscillation. The Stability Boundary Conditions chart (page 5) shows stable operation up to 100 nF only when cathode current is ≥10 mA. For low-current (<1 mA) applications, a 100 pF–1 nF ceramic capacitor from cathode to anode is recommended to suppress high-frequency ringing.