STMicroelectronics TL1431ACD

Overview

TL1431ACD from STMicroelectronics is a precision adjustable shunt voltage reference IC with 0.25% initial voltage accuracy, 2.5 V reference input voltage, and guaranteed operation from –20 °C to +70 °C. It delivers 1–100 mA sink current capability, 0.2 Ω typical dynamic impedance, and supports output voltage programming from 2.5 V to 36 V using two external resistors - widely used in isolated flyback feedback loops and programmable power supply regulation.

For engineers reviewing the TL1431ACD datasheet, TL1431ACD pinout, TL1431ACD application, or TL1431ACD equivalent, this page provides verified electrical parameters, SO-8 package terminal mapping, automotive-grade thermal stability data, and real-world design context for feedback path implementation and voltage setpoint accuracy validation.

Technical Context

The TL1431ACD functions as a 2.5 V bandgap-referenced error amplifier with internal NPN transistor output stage, configured as a 3-terminal shunt regulator. Its reference input (REF) compares against an external resistor divider, while cathode (K) and anode (A) terminals form the regulated shunt path across the primary-side optocoupler in isolated DC/DC converters.

It operates with a minimum cathode current of 0.5 mA for regulation, exhibits ±13 ppm/°C temperature coefficient, and maintains <0.5 Ω dynamic impedance up to 100 mA sink current - enabling stable closed-loop response under varying load and line conditions without external compensation in most applications.

Key Specifications

Pinout & Package

TL1431ACD is supplied in SO-8 batwing plastic micropackage (ECOPACK® compliant), offering improved thermal dissipation (R_thJA = 85 °C/W) and board-level reliability versus TO-92 variants. Pin 1 is Anode, Pin 2 is Cathode, Pin 3 is Reference (REF), Pins 4–8 are NC (no connection) per Figure 2 of ST's datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431ACDR and AS431AT, TL1431ACD offers superior initial accuracy and lower dynamic impedance at commercial temperature range, making it optimal for cost-sensitive yet precision-critical isolated power supplies where thermal management is controlled.

Availability

TL1431ACD is available at Aetrix Electronics and suitable for isolated flyback feedback, programmable lab power supplies, overvoltage protection circuits, and current source reference designs requiring stable component supply with consistent parametric performance across production lots.

Supply support for TL1431ACD 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 management ICs, analog components, and MEMS sensors for industrial, automotive, and consumer markets.

The TL1431 product line delivers precision shunt references optimized for feedback path accuracy and stability in isolated power conversion - targeting cost-effective, high-reliability regulation in AC/DC adapters, telecom PSUs, and industrial SMPS.

FAQ

What is the minimum cathode current required for regulation in TL1431ACD?

The TL1431ACD requires a minimum cathode current of 0.5 mA to maintain regulation, as specified in Table 4 of the ST datasheet (DocID5286 Rev 9). Below this threshold, the device exits regulation mode and output voltage becomes undefined. This value is validated across –20 °C to +70 °C and applies regardless of external resistor values or output voltage setting.

Can TL1431ACD replace TL431 in existing designs without layout changes?

Yes - TL1431ACD uses the same SO-8 batwing footprint and pinout (Anode–Cathode–REF on Pins 1–2–3) as TI's TL431ACDR, enabling drop-in replacement. However, its lower dynamic impedance (0.2 Ω vs. 0.35 Ω) and tighter 0.25% accuracy may require minor loop compensation review in high-bandwidth feedback paths.

Does TL1431ACD support operation above 36 V cathode-to-anode voltage?

No - the absolute maximum cathode-to-anode voltage (V_KA) is 37 V per Table 1, and recommended operating range is limited to V_REF to 36 V (Table 2). Exceeding 36 V risks exceeding power dissipation limits and degrading long-term reliability, even if instantaneous voltage remains below 37 V.

How does the REF pin input current vary with temperature in TL1431ACD?

REF pin input current (I_REF) ranges from 1.5 µA to 3 µA at 25 °C and varies by ≤1.2 µA over –20 °C to +70 °C (ΔI_REF = 0.2–1.2 µA in Table 4). This low, tightly bounded current minimizes resistor-divider error and enables use of high-value feedback resistors without significant temperature-induced setpoint drift.