STMicroelectronics TL431IYDT

Overview

TL431IYDT from STMicroelectronics is an AEC-Q100 qualified automotive-grade adjustable shunt voltage reference IC, operating as a precision 2.5 V reference with programmable output up to 36 V via external resistors. It delivers 1–100 mA sink current capability, 0.22 Ω typical dynamic impedance, and ±2% initial voltage accuracy across –40 °C to +125 °C - used in feedback loops of isolated DC-DC converters and battery management systems.

For engineers reviewing the TL431IYDT datasheet, TL431IYDT pinout, TL431IYDT application, or TL431IYDT equivalent, key selection criteria include automotive temperature compliance, shunt regulation stability under variable load, dynamic impedance impact on loop response, and SO-8 package thermal performance in high-reliability power supply designs.

Technical Context

The TL431IYDT functions as a three-terminal adjustable shunt regulator: its REF pin senses voltage against an internal 2.5 V bandgap reference; cathode sinks current when REF exceeds threshold; anode connects to ground or return path. It operates without external compensation in most configurations but requires ≥0.5 mA minimum cathode current for regulation.

Its architecture integrates a precision comparator, bandgap reference, and NPN output stage. The device exhibits <30 mV reference voltage deviation over –40 °C to +125 °C and maintains ≤0.5 Ω dynamic impedance across 1–100 mA cathode current range, enabling stable error amplification in flyback and forward converter feedback networks.

Key Specifications

Pinout & Package

TL431IYDT is supplied in an SO-8 "batwing" plastic micropackage (ECOPACK® compliant), offering improved thermal resistance (R_thJA = 85 °C/W) versus TO-92 or SOT-23 variants. Its 8-pin layout supports robust PCB layout for high-current shunt operation and EMI-sensitive feedback nodes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431IYDT, TL431BIDT improves voltage accuracy at the cost of higher unit price and identical thermal behavior, while TL432IYDT trades simplicity for active output flexibility - making TL431IYDT optimal for cost-sensitive, thermally constrained automotive shunt regulation.

Availability

TL431IYDT is available at Aetrix Electronics and suitable for automotive power supplies, industrial SMPS feedback circuits, and battery management systems requiring stable component supply with AEC-Q100 compliance and extended temperature support.

Supply support for TL431IYDT 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog components for automotive, industrial, and consumer markets.

The TL431 product line delivers precision voltage references optimized for feedback control in regulated power supplies - specifically engineered for reliability, thermal stability, and seamless integration into safety-critical automotive and industrial systems.

FAQ

What is the minimum cathode current required for regulation in TL431IYDT?

The TL431IYDT requires a minimum cathode current of 0.5 mA to maintain regulation, as specified in Table 6 of the STMicroelectronics datasheet (DocID4467 Rev 17). This value holds across the full –40 °C to +125 °C operating range and ensures stable reference behavior even at cold temperatures and light loads.

Can TL431IYDT replace TL431CDT in existing designs?

TL431IYDT is not a direct drop-in replacement for TL431CDT due to differing temperature ranges (–40 °C to +125 °C vs. 0 °C to +70 °C) and accuracy grades (±2% vs. ±2% but different test conditions). While pinout and basic function match, thermal validation and long-term drift characterization must be re-performed for automotive or extended-temperature use cases.

Does TL431IYDT require external capacitors for stability?

No external capacitor is required for basic shunt regulation stability. However, STMicroelectronics recommends adding a 10 nF ceramic capacitor between REF and cathode when driving capacitive loads >100 pF or operating in noisy environments - as shown in Figure 21 of the datasheet - to prevent oscillation and ensure phase margin >45°.

What is the maximum power dissipation for TL431IYDT in SO-8 package?

In SO-8 package, TL431IYDT has a junction-to-ambient thermal resistance (R_thJA) of 85 °C/W. With a maximum junction temperature of 150 °C and 25 °C ambient, maximum allowable power dissipation is (150–25)/85 ≈ 1.47 W. At 100 mA cathode current and 36 V cathode-anode voltage, power dissipation reaches 3.6 W - requiring derating or heatsinking beyond ambient 25 °C.