Diodes Incorporated ZTL431AFFTA

Overview

ZTL431AFFTA from Diodes Incorporated is a 1% initial tolerance, adjustable precision shunt regulator in SOT23F package, delivering 2.5V reference voltage with ±0.5% deviation over −40°C to +125°C, 0.2Ω typical dynamic output impedance, and 1–100mA cathode sink current - used for voltage regulation and feedback in isolated DC-DC converters.

For engineers reviewing the ZTL431AFFTA datasheet, ZTL431AFFTA pinout, ZTL431AFFTA application, or ZTL431AFFTA equivalent, key selection criteria include reference voltage accuracy across temperature, cathode current capability at 20V max VKA, stability with capacitive loads, and SOT23F footprint compatibility in space-constrained power control circuits.

Technical Context

The ZTL431AFFTA implements a bandgap-based 2.5V reference with internal error amplifier and NPN output stage, enabling precise shunt regulation via external resistor divider. It operates as a programmable zener replacement with active feedback control rather than passive breakdown.

Its architecture supports stable operation up to 20V cathode-anode voltage and maintains regulation down to 0.4mA minimum cathode current. Stability requires ≥4.7nF anode–cathode capacitance per manufacturer guidance to avoid oscillation in the 10Hz–1MHz range.

Key Specifications

Pinout & Package

SOT23F package: 3-pin, surface-mount, gull-wing leads; thermal resistance θJA = 138°C/W; power dissipation rating 900mW at TA = +25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431ACDBVR, ZTL431AFFTA trades 16V headroom for 1% accuracy and automotive-grade temp range; versus ZTL431BFFTA, it offers cost savings where ±1% VREF deviation is sufficient for closed-loop stability margins.

Availability

ZTL431AFFTA is available at Aetrix Electronics and suitable for isolated DC-DC feedback, optocoupler linearization, and overvoltage protection circuits requiring stable component supply with guaranteed long-term manufacturability.

Supply support for ZTL431AFFTA 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 semiconductor company specializing in discrete, analog, and mixed-signal devices, with design centers in Asia, Europe, and the U.S., serving industrial, computing, and automotive markets.

ZTL431AFFTA belongs to Diodes' precision reference product line, engineered for high-accuracy shunt regulation in cost-sensitive, thermally demanding power management applications where reliability and RoHS compliance are mandatory.

FAQ

What is the minimum cathode current required for regulation?

The ZTL431AFFTA requires a minimum cathode current of 0.4mA to maintain regulation, verified per Electrical Characteristics table at TA = +25°C. Below this level, reference voltage may deviate beyond specified tolerance, especially near temperature extremes. This value is critical for sizing the upper resistor in the feedback divider to ensure sufficient current under no-load conditions.

Can ZTL431AFFTA replace TL431 in existing designs?

ZTL431AFFTA is functionally compatible with TL431 in most circuits but has a lower 20V maximum cathode voltage versus TL431's 36V. Pinout matches TL431 in SOT23F, and its 1% VREF tolerance and −40°C to +125°C range exceed standard TL431AC specifications. Verify VKA stress margins before drop-in replacement.

Why is a 4.7nF capacitor required between anode and cathode?

A ≥4.7nF capacitor across anode–cathode is required to suppress instability observed in gain vs. frequency measurements, particularly above 10kHz. Without it, phase margin drops below 45°, risking oscillation in feedback loops. This capacitor does not affect DC regulation but is essential for reliable transient response in switching power supplies.

How does the SOT23F package differ from standard SOT23 for ZTL431?

SOT23F has wider lead spacing (e1 = 1.90mm vs. SOT23's 1.83mm) and larger body dimensions (2.90 × 2.40mm vs. 2.90 × 2.40mm same length/width but different lead geometry), resulting in lower thermal resistance (138°C/W vs. 380°C/W) and higher 900mW power dissipation. Layout must use SOT23F-specific pad dimensions per AP02002.