Texas Instruments TL431CPKE6

Overview

TL431CPKE6 from Texas Instruments is a precision programmable shunt voltage reference IC in SOT-89-3 package, delivering 2.495 V nominal reference voltage with ±0.5% initial tolerance (B grade), 0.2 Ω typical dynamic impedance, and operation across −40°C to 125°C. It replaces Zener diodes in feedback loops of isolated DC/DC converters, AC/DC power supplies, and servo drive control modules.

For engineers reviewing the TL431CPKE6 datasheet, TL431CPKE6 pinout, TL431CPKE6 application, or TL431CPKE6 equivalent, key selection criteria include its adjustable output range (2.5 V to 36 V), low temperature drift (14 mV over −40°C to 125°C), sink-current capability (1–100 mA), and SOT-89 thermal performance (R_θJC = 9 °C/W).

Technical Context

The TL431CPKE6 implements a high-gain transconductance amplifier with internal 2.495 V bandgap reference, comparing REF pin voltage to V_ref and driving the cathode to maintain regulation via external resistor divider. Its active output stage provides sharp turn-on and stable closed-loop behavior in switching power supply feedback networks.

Designed for high-reliability industrial and automotive applications, it supports wide-cathode-voltage operation (up to 36 V), exhibits low 1/f noise (≤1 µV_PP over 0.1–10 Hz), and maintains <0.5 Ω dynamic impedance up to 100 mA sink current - enabling precise error amplification without external compensation in many topologies.

Key Specifications

Pinout & Package

SOT-89-3 package: 3-pin thermally enhanced plastic surface-mount package with exposed pad for improved heat dissipation (R_θJC = 9 °C/W). Pin 2 (ANODE) is internally connected to substrate and must be tied to system ground or left open per layout guidelines.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431CPKE6, TL431CDBZR trades accuracy and temperature range for cost and size, while TL431BQDBZR matches performance in a smaller footprint but requires careful thermal management due to higher junction-to-ambient resistance.

Availability

TL431CPKE6 is available at Aetrix Electronics and suitable for rack server power, industrial AC/DC, and servo drive control applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for TL431CPKE6 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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision analog ICs and power management solutions.

The TL431 product line was engineered as a drop-in Zener replacement for high-stability voltage regulation in power supply feedback loops, targeting industrial, automotive, and telecom infrastructure applications.

FAQ

What is the reference voltage tolerance of TL431CPKE6 at 25°C?

The TL431CPKE6 has a ±0.5% initial reference voltage tolerance at 25°C, corresponding to a 2.495 V nominal value with ±12.5 mV deviation. This B-grade specification is confirmed in Section 6.11 of the TI SLVS543S datasheet and applies specifically to the Q-temp (−40°C to 125°C) variant in SOT-89-3 packaging. The tolerance remains stable across temperature due to internal bandgap design.

Can TL431CPKE6 replace a Zener diode in feedback circuits?

Yes, TL431CPKE6 is explicitly designed as a superior Zener diode replacement in feedback circuits. Its active transconductance amplifier architecture delivers sharper turn-on, lower dynamic impedance (0.2 Ω vs typical Zener's >10 Ω), and tighter voltage tolerance (±0.5% vs ±5% for standard Zeners). It operates reliably in isolated flyback, forward, and LLC converter feedback paths using an optocoupler interface.

What is the maximum cathode voltage rating for TL431CPKE6?

The absolute maximum cathode-to-anode voltage (V_{K A}) for TL431CPKE6 is 37 V, with recommended operating range from V_ref (≈2.5 V) to 36 V. This rating is specified in Section 6.1 of the TI SLVS543S datasheet and enables use in 24 V, 48 V, and 36 V industrial bus systems without external clamping circuitry.

Does TL431CPKE6 require external capacitors for stability?

TL431CPKE6 can operate stably without external capacitors in most configurations, but Figure 6-18 of the datasheet defines stability boundaries dependent on load capacitance (C_L) and cathode current (I_KA). For C_L > 10 nF and I_KA > 10 mA, a small series resistor (e.g., 10–100 Ω) between cathode and optocoupler LED is recommended to suppress potential oscillation - verified in TI application note SLVA612.

How does the SOT-89-3 package of TL431CPKE6 improve thermal performance?

The SOT-89-3 package of TL431CPKE6 features an exposed thermal pad that achieves R_θJC = 9 °C/W - significantly lower than SOT-23-3 (R_θJC = 76 °C/W) or SOIC-8 (R_θJC = 39 °C/W). This allows sustained 100 mA sink current at elevated ambient temperatures (up to 125°C) without derating, making it ideal for thermally demanding servo drive and inverter applications.