Texas Instruments TL431ACDBZR

Overview

TL431ACDBZR from Texas Instruments is a precision programmable shunt voltage reference in SOT-23-3 package, delivering 2.495 V nominal reference voltage with ±0.5% initial tolerance at 25°C, 1 mA to 100 mA sink-current capability, and operation across −40°C to 85°C. It serves as a stable feedback element in isolated DC-DC converters, AC/DC power supplies, and voltage-monitoring circuits.

For engineers reviewing the TL431ACDBZR datasheet, TL431ACDBZR pinout, TL431ACDBZR application, or TL431ACDBZR equivalent, key selection criteria include its 0.2 Ω dynamic impedance, low 2 µA reference input current, 14 mV max reference voltage drift over temperature, and compatibility with standard resistor-divider feedback networks in flyback and forward converter topologies.

Technical Context

The TL431ACDBZR implements an internal error amplifier and NPN transistor output stage configured as an adjustable shunt regulator. Its REF pin senses voltage relative to ANODE, triggering cathode current conduction when the divider output exceeds V_ref. The device operates in active regulation mode only when cathode-to-anode voltage (V_KA) remains between 2.5 V and 36 V and minimum cathode current (0.4–0.6 mA) is maintained.

Unlike Zener diodes, it provides sharp turn-on characteristics and low output impedance (0.2 Ω typ), enabling precise closed-loop control in secondary-side feedback paths. Its SOT-23-3 pinout (REF–CATHODE–ANODE) is distinct from TL432 variants and incompatible with SOIC or PDIP packages without layout revision.

Key Specifications

Pinout & Package

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

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL431AIDBZR, TL431ACDBZR delivers tighter regulation accuracy at no layout change; versus TL431BIDBZR, it reduces cost and thermal derating overhead in standard industrial applications where 85°C ambient is sufficient.

Availability

TL431ACDBZR is available at Aetrix Electronics and suitable for rack server power, industrial AC/DC converters, and notebook PC adapter designs requiring stable component supply, long-term production continuity, and RoHS-compliant sourcing.

Supply support for TL431ACDBZR 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 ICs, with decades of expertise in precision reference design and high-reliability power solutions.

The TL431 product line was engineered specifically for high-accuracy, low-drift shunt regulation in isolated power supplies, battery management, and voltage supervision systems - emphasizing stability, noise immunity, and wide-temperature operation.

FAQ

What is the reference voltage tolerance of TL431ACDBZR at 25°C?

The TL431ACDBZR has a reference voltage tolerance of ±0.5% at 25°C, corresponding to a 2.470 V to 2.520 V range around the nominal 2.495 V output. This A-grade precision enables accurate voltage setting in feedback networks without post-manufacturing trimming. The TL431ACDBZR maintains this specification under recommended operating conditions with 10 mA cathode current and V_KA = V_ref.

Can TL431ACDBZR replace a Zener diode in power supply feedback circuits?

Yes, TL431ACDBZR is explicitly designed as a superior replacement for Zener diodes in shunt-regulator applications. Its 0.2 Ω dynamic impedance, sharp turn-on, and 2 µA reference input current provide significantly better regulation accuracy, temperature stability, and noise performance than discrete Zeners. The TL431ACDBZR achieves this while maintaining pin-compatible implementation in SOT-23-3 layouts originally intended for Zener-based designs.

What is the maximum cathode-to-anode voltage rating for TL431ACDBZR?

The absolute maximum cathode-to-anode voltage (V_KA) for TL431ACDBZR is 37 V, with recommended operating range from V_ref (≈2.5 V) up to 36 V. Exceeding 37 V risks permanent damage. This rating allows safe operation in 24 V and 36 V industrial systems, including DC-link monitoring and high-output flyback converters where TL431ACDBZR regulates via resistor dividers scaled to stay within limits.

Does TL431ACDBZR require an external capacitor for stability?

TL431ACDBZR does not require an external capacitor for basic regulation, but stability depends on load capacitance and cathode current. Per TI's stability boundary curves (Figures 6-18), oscillation risk increases above 10 µF capacitance at low cathode currents (<10 mA). For TL431ACDBZR in optocoupler-driven feedback, a 1 nF ceramic capacitor from cathode to anode is commonly used to suppress high-frequency ringing without compromising transient response.

How does the temperature coefficient of TL431ACDBZR compare to standard-grade TL431 devices?

TL431ACDBZR exhibits a maximum reference voltage deviation (VI(dev)) of 14 mV over −40°C to +85°C, translating to approximately 100 ppm/°C typical drift. Standard-grade TL431 (no suffix) shows up to 25 mV deviation in same range, while B-grade TL431BCDBZR achieves 6 mV (0°C to 70°C only). Thus, TL431ACDBZR delivers improved thermal stability over standard grade while balancing cost and extended temperature coverage beyond C-grade parts.