STMicroelectronics TL431CDT

Overview

TL431CDT from STMicroelectronics is an AEC-Q100-qualified, adjustable shunt voltage reference IC with 2% initial voltage accuracy (2.5 V to 36 V output range), 1–100 mA sink current capability, 0.22 Ω typical dynamic impedance, and operation across 0 °C to +70 °C. It serves as a precision feedback element in isolated DC-DC converters, linear regulators, and overvoltage protection circuits.

For engineers reviewing the TL431CDT datasheet, TL431CDT pinout, TL431CDT application, or TL431CDT equivalent, key selection criteria include its SO-8 batwing package thermal performance (R_thjc = 30 °C/W), cathode-to-anode voltage rating (37 V), minimum regulation current (0.5 mA), and automotive-grade qualification path-critical for industrial power supply design and BOM validation.

Technical Context

The TL431CDT implements a three-terminal adjustable shunt regulator architecture: the REF pin senses a resistive divider voltage, triggering internal error amplification and NPN transistor conduction to sink cathode current and clamp the output. Its bandgap-based reference core delivers stable 2.5 V nominal threshold with ±2% tolerance over temperature and line variations.

It operates in closed-loop feedback configurations where cathode voltage is regulated via external resistor networks, supporting both fixed and programmable output topologies. The device requires no external compensation in most applications due to inherent phase margin stability up to 100 kHz with capacitive loads ≤100 nF.

Key Specifications

Pinout & Package

TL431CDT is supplied in an SO-8 batwing plastic micropackage (ECOPACK® compliant), offering improved thermal dissipation (R_thjc = 30 °C/W) versus TO-92 or SOT-23 variants. The 8-pin layout includes dedicated NC pins for layout flexibility and enhanced creepage/clearance in high-voltage feedback paths.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431CDT, TL431ACDT improves absolute voltage accuracy at the expense of cost, while TL431IDT extends thermal robustness without altering regulation performance-enabling trade-offs between precision, environmental resilience, and BOM cost.

Availability

TL431CDT is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, and test equipment requiring stable component supply with SO-8 thermal performance and AEC-Q100 traceability.

Supply support for TL431CDT 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The TL431 product line delivers precision programmable shunt references optimized for feedback control in isolated power conversion, voltage monitoring, and current regulation-targeting cost-sensitive, high-reliability applications.

FAQ

What is the maximum cathode-to-anode voltage for TL431CDT?

The absolute maximum cathode-to-anode voltage (V_KA) is 37 V. Operation beyond this risks permanent breakdown of the internal NPN transistor. For 36 V nominal systems, ensure transient clamping or derating to maintain long-term reliability-designers commonly limit steady-state V_KA to ≤33 V with 10% margin.

Can TL431CDT replace TL431CZ in a TO-92 design?

No-TL431CDT uses an SO-8 package with different thermal resistance (R_thjc = 30 °C/W), pinout, and solder footprint than the TO-92 TL431CZ (R_thjc = 200 °C/W). Direct replacement requires PCB redesign, thermal revalidation, and layout review for creepage/clearance compliance in high-voltage feedback paths.

Does TL431CDT require external compensation for stability?

TL431CDT is internally compensated and remains stable with capacitive loads up to 100 nF when used in standard shunt regulator configurations. For loads >100 nF or high-frequency switching noise environments, add a 1–10 Ω series resistor between REF and divider node to damp oscillation-verified in ST's AN2152 application note.

How does the SO-8 batwing package improve thermal performance?

The SO-8 batwing package features enlarged copper leadframes and dual anode connections (Pins 1 and 8), reducing junction-to-case thermal resistance to 30 °C/W-2.8× better than TO-92 (200 °C/W). This allows 2.5× higher continuous power dissipation (up to 750 mW at 25 °C ambient) without heatsinking in compact power supply layouts.