STMicroelectronics TL431IZ

Overview

TL431IZ from STMicroelectronics is an AEC-Q100 qualified adjustable shunt voltage reference designed for automotive power regulation circuits. It delivers 2.5–36 V programmable output via two external resistors, supports 1–100 mA sink current, achieves 0.22 Ω typical dynamic impedance, and operates across –40 °C to +125 °C for engine control units and battery management systems.

For engineers reviewing the TL431IZ datasheet, TL431IZ pinout, TL431IZ application, or TL431IZ equivalent, key selection criteria include automotive-grade temperature stability, 2% initial voltage accuracy, TO-92 package thermal resistance (200 °C/W junction-to-ambient), and compatibility with feedback loops in isolated DC-DC converters and LDO supervision circuits.

Technical Context

The TL431IZ implements a precision bandgap reference core with an internal error amplifier driving an NPN output transistor in shunt configuration. Its reference input (REF) compares against an internal 2.495 V threshold, enabling closed-loop regulation when used with external resistor dividers.

It functions as a 3-terminal programmable zener: cathode carries load current, anode connects to ground or return path, and REF senses divided output voltage. The device maintains regulation only when cathode current stays ≥0.5 mA and cathode-to-anode voltage remains ≥2.5 V.

Key Specifications

Pinout & Package

TL431IZ is supplied in TO-92 plastic package (bulk or ammopack), with 3 leads: Cathode (pin 1), Anode (pin 2), Reference (pin 3). Thermal resistance is 200 °C/W junction-to-ambient, requiring heatsinking above ~500 mW dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431IZ, TL431ACZ trades automotive qualification for tighter 1% accuracy in identical through-hole packaging, while TL431BIL3T offers superior precision and smaller footprint at the cost of higher thermal resistance and different mounting requirements.

Availability

TL431IZ is available at Aetrix Electronics and suitable for automotive battery management, isolated flyback feedback, and industrial SMPS supervision requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for TL431IZ 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management solutions with broad manufacturing and quality certification infrastructure.

The TL431 product line targets cost-sensitive, high-reliability voltage regulation in automotive and industrial power systems, emphasizing AEC-Q100 compliance, wide temperature operation, and drop-in compatibility with legacy designs.

FAQ

What is the minimum cathode current required for regulation in TL431IZ?

The TL431IZ requires a minimum cathode current of 0.5 mA to maintain regulation, as specified in Table 3 and Table 5 of the datasheet. Below this threshold, the device exits active regulation mode and output voltage becomes uncontrolled. This value is confirmed across the full –40 °C to +125 °C operating range and applies regardless of output voltage setting.

Can TL431IZ replace TL431CZ in existing designs?

Yes, TL431IZ can directly replace TL431CZ in most cases because both share identical TO-92 packaging, pinout, and electrical characteristics except for temperature range and qualification. TL431IZ extends operation to +125 °C and adds AEC-Q100 qualification, making it suitable for upgraded automotive applications without circuit modification.

How does the 2% voltage accuracy affect feedback loop design?

The 2% initial reference voltage tolerance contributes directly to output voltage error in shunt-regulated supplies. For a 12 V output set by R1/R2, this introduces ±240 mV uncertainty before considering resistor tolerance and temperature drift. Designers must allocate remaining error budget accordingly-typically using 0.5% or 1% resistors and accounting for thermal coefficient mismatch.

What is the maximum power dissipation for TL431IZ in TO-92 package?

Maximum power dissipation is limited by thermal resistance: R_thja = 200 °C/W and maximum junction temperature T_J = 150 °C. With ambient at +85 °C, allowable ΔT = 65 °C, yielding P_max ≈ 325 mW. Derating is required above 50 °C ambient; at +105 °C ambient, safe continuous dissipation drops to ~225 mW.