Nexperia USA Inc. TL431BFDT-QR

Overview

TL431BFDT-QR from Nexperia is a B-grade (±0.5 %) adjustable precision shunt regulator in SOT23 package, featuring 2.495 V reference voltage, 0.2 Ω dynamic cathode-anode impedance, and 1 mA to 100 mA sink current capability. It operates across –40 °C to +125 °C and is AEC-Q100 Grade 1 qualified for automotive feedback loops and on-board regulation.

For engineers reviewing the TL431BFDT-QR datasheet, TL431BFDT-QR pinout, TL431BFDT-QR application, or TL431BFDT-QR equivalent, key selection criteria include reference voltage tolerance (0.5 %), thermal stability over –40 °C to +125 °C, cathode-anode voltage range (2.495 V to 36 V), and compatibility with isolated SMPS feedback networks requiring low-output-impedance shunt control.

Technical Context

The TL431BFDT-QR implements a precision bandgap-based reference amplifier driving an NPN output stage, enabling sharp turn-on and stable regulation at programmable voltages set by two external resistors. Its functional diagram confirms direct cathode–anode–reference terminal topology without internal pass transistors or compensation pins.

It delivers 0.2 Ω typical dynamic impedance below 1 kHz and maintains reference voltage drift ≤ ±17 mV over –40 °C to +125 °C, supporting high-accuracy closed-loop control where Zener diodes lack stability and repeatability.

Key Specifications

Pinout & Package

SOT23 plastic surface-mounted package (3 leads); compact 2.9 mm × 1.3 mm footprint with standard lead pitch (0.95 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431BQDBZR-Q, TL431BFDT-Q offers identical performance in a mirrored-pin variant optimized for space-constrained layouts; versus TL431ACDBZR-Q, it trades higher cost for tighter tolerance and extended temperature capability essential in automotive and industrial deployments.

Availability

TL431BFDT-QR is available at Aetrix Electronics and suitable for automotive on-board chargers, industrial isolated DC-DC converters, and programmable bench power supplies requiring stable component supply with AEC-Q100 compliance and long-term lifecycle support.

Supply support for TL431BFDT-QR 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

Nexperia is a global semiconductor expert delivering high-performance, reliable discrete, logic, and MOSFET solutions with focus on efficiency, reliability, and miniaturization.

The TL431-Q family belongs to Nexperia's automotive-qualified precision analog portfolio, designed specifically for robust voltage reference and feedback control in harsh-environment power systems including EV charging, ADAS, and industrial automation.

FAQ

What is the maximum cathode-anode voltage for TL431BFDT-QR?

The absolute maximum cathode-anode voltage is 37 V per IEC 60134 limiting values. The recommended operating range extends from V_ref (2.495 V) up to 36 V. Exceeding 37 V risks permanent device damage, while operation near 36 V requires thermal derating per Figure 2 - especially on FR4 PCBs without enhanced heatsinking.

Does TL431BFDT-QR require an external capacitor on the REF pin?

Yes - a 100 pF capacitor is recommended directly at the REF pin to suppress high-frequency noise coupling from primary-side switching transients, particularly in SMPS feedback applications (per Figure 26). Larger capacitors (>1 nF) may cause instability; this value balances noise immunity and loop stability without compensation network redesign.

How does the mirrored pinout (MFDT) differ from standard SOT23 pinning?

TL431BFDT-QR uses mirrored pinning: Pin 1 = REF, Pin 2 = K, Pin 3 = A - reversing the standard K-REF-A order found in DBZR variants. This layout reduces trace length between REF and divider resistors in dense layouts but mandates matching footprint design; mixing footprints causes functional failure due to reversed reference and cathode connections.

Can TL431BFDT-QR replace a Zener diode in existing designs?

Yes - it replaces Zener diodes in applications requiring better than ±5 % tolerance, low dynamic impedance, or temperature-stable regulation. Unlike Zeners, it needs only two external resistors for voltage setting and draws minimal reference current (2–4 µA), reducing divider power loss. However, its three-terminal topology requires verifying anode grounding and REF node routing - direct drop-in replacement is not possible without schematic and layout review.