Texas Instruments TL431BCDCKR

Overview

TL431BCDCKR from Texas Instruments is a precision programmable shunt voltage reference IC in SOT-23-3 package, featuring 0.5% initial reference voltage tolerance at 25°C, adjustable output from 2.495 V to 36 V, and operation across −40°C to 125°C. It delivers 0.2 Ω typical dynamic impedance and supports 1–100 mA sink current, widely used in feedback loops of isolated DC/DC converters and AC/DC power supplies.

For engineers reviewing the TL431BCDCKR datasheet, TL431BCDCKR pinout, TL431BCDCKR application, or TL431BCDCKR equivalent, key selection criteria include reference accuracy grade (B), thermal stability over extended temperature range, low output impedance for tight regulation, and compatibility with standard resistor-divider feedback networks in switching regulator designs.

Technical Context

The TL431BCDCKR implements a three-terminal adjustable shunt regulator architecture with an internal error amplifier, reference voltage source, and NPN output transistor. Its REF pin senses voltage relative to ANODE, triggering cathode current conduction when the divider ratio exceeds V_REF ≈ 2.495 V.

It operates as a high-gain, low-drift comparator driving a buffered cathode output - enabling sharp turn-on behavior and stable closed-loop regulation without external compensation in most applications. The B-grade device guarantees ≤±6 mV total reference deviation over 0°C to 70°C (C-temp) and ≤±14 mV over −40°C to 125°C (Q-temp).

Key Specifications

Pinout & Package

SOT-23-3 package (2.90 mm × 1.30 mm), surface-mount, lead-free, RoHS-compliant. Pin 1 = CATHODE, Pin 2 = REF, Pin 3 = ANODE.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431BIDCKR and TL431BCDBVR, TL431BCDCKR uniquely combines B-grade 0.5% accuracy, −40°C to 125°C operation, and compact SOT-23-3 packaging - making it optimal for thermally demanding, size-sensitive power feedback applications where long-term stability and board area are critical.

Availability

TL431BCDCKR is available at Aetrix Electronics and suitable for AC/DC power supplies, isolated DC/DC converters, and programmable overvoltage protection circuits requiring stable component supply and guaranteed long-term manufacturability.

Supply support for TL431BCDCKR 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, embedded processing, and power management technologies, with decades of experience in precision reference and power IC design.

The TL431 product line was engineered specifically for high-accuracy, low-drift voltage regulation in feedback paths of switching power supplies, replacing discrete Zener-based solutions with superior thermal stability and tighter tolerances.

FAQ

What is the reference voltage tolerance of TL431BCDCKR at 25°C?

The TL431BCDCKR has a reference voltage tolerance of ±0.5% at 25°C, corresponding to a nominal 2.495 V output with a guaranteed range of 2.483 V to 2.507 V. This B-grade accuracy is specified in Section 6.11 of the TI datasheet SLVS543S and applies strictly to the TL431BCDCKR variant in SOT-23-3 packaging. TL431BCDCKR maintains this precision across its full operating temperature range when used within recommended conditions.

Can TL431BCDCKR replace a Zener diode in voltage regulation circuits?

Yes, TL431BCDCKR is explicitly designed as a superior replacement for Zener diodes in shunt regulation applications. Its active circuitry provides sharper turn-on, lower dynamic impedance (0.2 Ω vs typical Zener's >10 Ω), and far better temperature stability (±6 mV over 0°C–70°C). TL431BCDCKR achieves this while maintaining identical three-terminal topology and simple two-resistor programming - enabling direct drop-in upgrades in existing Zener-based feedback networks without redesign.

What is the maximum cathode voltage rating for TL431BCDCKR?

The absolute maximum cathode-to-anode voltage (V_{K A}) for TL431BCDCKR is 37 V, with recommended operating range from V_REF (≈2.495 V) up to 36 V. Exceeding 37 V risks permanent damage per Section 6.1 of the datasheet. This rating allows TL431BCDCKR to interface safely with 24 V, 32 V, and 36 V rails in industrial and telecom power systems while maintaining regulation integrity.

Does TL431BCDCKR require external compensation for stability?

No, TL431BCDCKR is internally compensated and stable with capacitive loads up to 10 nF when used in standard feedback configurations. Figure 6-18 in the datasheet confirms stability boundaries for TL431B-grade SOT-23 devices, showing no oscillation risk under typical optocoupler-driven conditions. TL431BCDCKR does not require external phase compensation components unless driving >100 nF loads or operating in high-gain, low-current modes outside recommended conditions.

How does the REF pin input current affect TL431BCDCKR accuracy?

The REF pin input current of TL431BCDCKR is 2–4 µA at 25°C, contributing directly to resistor-divider error. For example, using 10 kΩ/10 kΩ feedback resistors introduces ~20 mV offset - corrected by selecting lower resistor values or applying calibration. This low I_REF enables high-impedance networks that minimize power loss while preserving accuracy, and TL431BCDCKR's tight 0.5% V_REF tolerance ensures overall system error remains within specification even with typical divider mismatches.