Texas Instruments TL431CDR

Overview

TL431CDR from Texas Instruments is a precision programmable shunt voltage reference IC with 2.495 V nominal reference voltage, ±1% initial tolerance at 25°C (A grade), and operation across −40°C to 85°C. It delivers 1–100 mA sink current, 0.2 Ω typical dynamic impedance, and supports adjustable output from 2.495 V to 36 V using two external resistors-commonly used in feedback loops of isolated DC/DC converters and notebook power adapters.

For engineers reviewing the TL431CDR datasheet, TL431CDR pinout, TL431CDR application, or TL431CDR equivalent, key selection criteria include its A-grade accuracy, I-temp range suitability for industrial AC/DC supplies, low temperature drift (14 mV over −40°C to 85°C), and SOT-23-3 package compatibility with space-constrained PCB layouts.

Technical Context

The TL431CDR implements an internal error amplifier and NPN transistor output stage configured as a three-terminal adjustable shunt regulator. Its REF pin senses voltage relative to the ANODE terminal, enabling precise regulation via external resistor divider feedback. The device operates in active shunt mode only when cathode-to-anode voltage exceeds ~2.5 V and cathode current remains above 0.4 mA.

It features sharp turn-on characteristics due to active output circuitry-making it a functional replacement for Zener diodes in closed-loop regulation. Unlike fixed references, TL431CDR requires no external biasing beyond the feedback network and maintains stable performance up to 100 mA sink current without external compensation under typical load capacitance conditions.

Key Specifications

Pinout & Package

TL431CDR is supplied in the SOT-23-3 package (2.90 mm × 1.30 mm), with gull-wing leads and moisture sensitivity level 1. Pin 1 = CATHODE, Pin 2 = ANODE, Pin 3 = REF - matching the standard TL431 pinout (not TL432).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431CDR, TL431ACDR offers identical electrical specs but larger package and worse thermal performance, while TLVH431IDBVR trades reference voltage flexibility and temperature range for tighter initial tolerance-neither is pin-compatible drop-in replacement, requiring layout or schematic revision.

Availability

TL431CDR is available at Aetrix Electronics and suitable for rack server power, industrial AC/DC, and notebook PC power adapter designs requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for TL431CDR 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 company specializing in analog and embedded processing technologies, with leadership in power management, signal chain, and high-reliability components.

The TL431 product line was designed for precision voltage regulation in isolated power supplies, feedback control systems, and programmable reference applications-emphasizing accuracy, thermal stability, and ease of integration across industrial and computing markets.

FAQ

What is the reference voltage tolerance of TL431CDR at 25°C?

The TL431CDR has a ±1% initial reference voltage tolerance at 25°C, corresponding to a 2.470 V to 2.520 V range. This A-grade specification is confirmed in Section 6.8 of the TI datasheet (SLVS543S) and applies specifically to the CDR variant with I-temp rating. TL431CDR's tolerance is tighter than standard-grade (±2%) but looser than B-grade (±0.5%), balancing cost and precision for industrial power applications.

Does TL431CDR support operation below −40°C?

No, TL431CDR is rated for operation from −40°C to +85°C (I grade), and its electrical characteristics are not guaranteed outside this range. While some units may function at −45°C, TI does not characterize or warrant performance below −40°C. For extended low-temperature use, consider TL431BQ or TL431AQ variants qualified down to −40°C with full spec validation across the full range.

What is the minimum cathode current required for TL431CDR to regulate?

The TL431CDR requires a minimum cathode current of 0.4–0.7 mA to maintain regulation, depending on temperature and operating conditions. This value is specified in Sections 6.8–6.10 of the datasheet under "Imin" and reflects the lowest current at which the internal amplifier remains active. Below this threshold, the device exits regulation and cathode voltage rises toward the input rail.

Can TL431CDR replace a Zener diode directly in existing circuits?

Yes, TL431CDR can directly replace Zener diodes in most shunt regulation applications, but requires attention to pinout (CATHODE/ANODE/REF vs. anode/cathode) and minimum current requirements. Unlike passive Zeners, TL431CDR needs ≥0.4 mA cathode current and a resistor divider on REF to set voltage-no change to cathode/anode connections is needed if the Zener was used in reverse-bias shunt mode.

Is TL431CDR pin-compatible with TL432 devices?

No, TL431CDR is not pin-compatible with TL432 variants. TL432 uses reversed pinout in SOT-23-3 (CATHODE/REF/ANODE), whereas TL431CDR uses CATHODE/ANODE/REF. Swapping them causes immediate malfunction or damage. Always verify pin configuration using Table 5-1 in the TI datasheet-TL431CDR belongs to the TL431 family and must be used with TL431-specific layouts.