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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Reference

STMicroelectronics TL431CZT

Name: TL431CZT
Brand: STMicroelectronics
SKU: TL431CZT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TL431CZT

Manufacturer:: STMicroelectronics

Category:: Voltage Reference

Package:: TO-226-2, TO-92-2 (TO-226AC)

Datasheet:: TL431CZT.pdf

Description:: IC VREF SHUNT ADJ 2.21% TO92-3

Quantity:: RFQ Add To RFQ list

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Inventory:14,156

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Product details

Overview

TL431CZT from STMicroelectronics is an AEC-Q100 qualified automotive-grade adjustable shunt voltage reference in TO-92 plastic package, delivering 2.5–36 V output via two external resistors, with 1% initial voltage precision, 100 mA sink current capability, and 0.22 Ω typical dynamic impedance - used for feedback regulation in isolated DC-DC converters and automotive body control modules.

For engineers reviewing the TL431CZT datasheet, TL431CZT pinout, TL431CZT application, or TL431CZT equivalent, key selection criteria include its -40 °C to +70 °C operating range (TL431C grade), TO-92 thermal resistance (R_thja = 200 °C/W), cathode-to-anode voltage rating (37 V), and reference input current (≤5.2 µA).

Technical Context

The TL431CZT operates as a 2.5 V bandgap-referenced error amplifier with internal NPN transistor output stage, configured as a programmable shunt regulator. Its reference input (REF) compares against an external resistor divider, controlling cathode current to maintain setpoint voltage across the anode–cathode terminals.

It functions within 1–100 mA cathode current range while maintaining stable regulation down to 0.5 mA minimum operating current. Temperature stability is achieved through curvature-compensated bandgap core, yielding ±17 mV reference deviation over 0 °C to +70 °C.

Key Specifications

Parameter	Value and Actual Design Meaning
Reference Voltage	2.47–2.52 V at 25 °C (1% tolerance grade TL431C; sets precise feedback threshold)
Voltage Range	2.5–36 V programmable output (via R1/R2 divider; enables wide-range supply monitoring)
Sink Current	1–100 mA cathode current (supports direct optocoupler drive in flyback feedback loops)
Dynamic Impedance	0.22 Ω typical (ensures low-output-impedance regulation under load transients)
Temp Range	0 °C to +70 °C operating (TL431C grade; suitable for commercial/industrial power supplies)
Thermal Resistance	R_thja = 200 °C/W (TO-92 package; requires heatsinking above ~250 mW dissipation)
Ref Input Current	≤5.2 µA max (minimizes divider loading error; enables high-resistor-value programming)

Pinout & Package

TL431CZT uses TO-92 plastic package (3-pin, through-hole), with standard pinout: Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Reference (REF). Package dimensions: 4.7 mm height × 3.8 mm diameter, lead pitch 1.27 mm.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Anode)	Anode terminal	Connected to system ground or low-side return; completes shunt current path
Pin 2 (Cathode)	Cathode terminal	Carries regulated sink current; drives optocoupler LED or error amplifier input
Pin 3 (REF)	Reference input	High-impedance comparator input; connected to resistor divider midpoint for voltage sensing

Key Features

Feature	Design Value
AEC-Q100 qualification	Validated for automotive applications including BCM and lighting control (though TL431C grade is commercial-temp; full AEC compliance applies to TL431IY variants)
Adjustable output	2.5–36 V range with only two external resistors - eliminates need for multiple fixed-reference SKUs
Low dynamic impedance	0.22 Ω typical ensures <10 mV output shift under 100 mA load step - critical for tight-regulation SMPS
Wide cathode current range	1–100 mA operation supports both low-power sensing and high-gain optocoupler drive without external buffer
Stable over temperature	±17 mV V_ref drift over 0–70 °C enables reliable feedback in unheated enclosures

Applications

AC-DC Adapter Feedback

Automotive Cabin Lighting Control

Use Scenario: Regulates output voltage in 12 V input, 5 V/3 A flyback converter using PC817 optocoupler feedback loop.

IC Role / Device Role / Timing Role: Shunt reference providing precise error signal to optocoupler LED, enabling primary-side regulation via secondary-side sensing.

Use Value: 0.22 Ω dynamic impedance minimizes output ripple under transient load steps; 1% V_ref ensures ±50 mV output accuracy.

Use Scenario: Senses battery voltage in LED headlamp driver to enable dimming below 11.5 V and disable above 16 V.

IC Role / Device Role / Timing Role: Adjustable voltage monitor comparing battery rail to programmable threshold; triggers MCU GPIO interrupt on over/under-voltage.

Use Value: 2.5–36 V programmability allows single BOM part to cover 12 V and 24 V vehicle platforms without redesign.

Industrial PLC Power Monitor

USB-C PD Sink Protection

Use Scenario: Detects undervoltage lockout (UVLO) on 24 V PLC backplane supply before enabling I/O module power sequencing.

IC Role / Device Role / Timing Role: Precision shunt reference feeding comparator input; provides clean, noise-immune trip point independent of supply rail variation.

Use Value: ≤5.2 µA reference current avoids loading of high-impedance divider; enables 1 MΩ+ resistor values for low quiescent power.

Use Scenario: Monitors CC line voltage during USB-C PD negotiation to detect invalid source V_CONN or faulty cable detection.

IC Role / Device Role / Timing Role: Programmable threshold detector clamping CC line at 2.5 V reference level to prevent false PD handshake initiation.

Use Value: TO-92 package allows compact placement near USB-C connector; 37 V cathode–anode rating withstands accidental 20 V transients.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TL431ACZT	1% initial tolerance (vs. TL431CZT's 2%), same TO-92 package and 0–70 °C range	Higher precision required in lab-grade power supplies where ±25 mV output error is unacceptable	Select when tighter reference accuracy is needed without changing layout or thermal design
TL431CL3T	SOT23-3 package, same 2% tolerance and 0–70 °C range; 136 °C/W junction-to-ambient thermal resistance	Suitable for space-constrained PCBs where TO-92 footprint is prohibitive, but requires derating above ~150 mW	Choose for surface-mount assembly and automated reflow; verify power dissipation margin with R_thja = 136 °C/W

Compared with TL431CZT, TL431ACZT improves voltage accuracy without thermal or footprint trade-offs, while TL431CL3T sacrifices thermal performance for miniaturization - making TL431CZT optimal for cost-sensitive through-hole designs needing moderate precision and robust thermal margin.

Availability

TL431CZT is available at Aetrix Electronics and suitable for AC-DC adapters, industrial PLC power monitors, and automotive cabin lighting control requiring stable component supply, long-term obsolescence management, and consistent TO-92 mechanical compatibility.

Supply support for TL431CZT 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.

TL431CZT belongs to ST's precision voltage reference product line, engineered for high-stability feedback in power conversion systems where accuracy, thermal robustness, and long-term reliability are essential.

FAQ

What is the maximum cathode-to-anode voltage for TL431CZT?

The absolute maximum cathode-to-anode voltage (V_KA) is 37 V. Operation beyond this risks permanent damage. In practice, continuous operation should remain ≤36 V per electrical characteristics tables, with sufficient derating margin for transients - especially in automotive environments where load-dump spikes may exceed 40 V.

Can TL431CZT replace TL431B in a design?

No - TL431B offers 0.5% initial tolerance and -40 °C to +125 °C operation, whereas TL431CZT is rated for 0 °C to +70 °C with 2% tolerance. Substituting TL431CZT into a TL431B design risks output inaccuracy outside temperature extremes and fails AEC-Q100 compliance requirements.

How does the REF pin function electrically?

The REF pin is the high-impedance input of an internal error amplifier, biased at 2.47–2.52 V. It draws ≤5.2 µA and must be driven by a resistor divider from cathode/anode nodes. Its voltage is compared to the internal bandgap reference; mismatch causes cathode current adjustment to restore equilibrium.

Is TL431CZT RoHS compliant and halogen-free?

Yes - TL431CZT is manufactured in ST's ECOPACK2-compliant TO-92 package, meeting RoHS Directive 2011/65/EU and halogen-free requirements per IEC 61249-2-21. Full material declarations and compliance certificates are available via ST's quality portal upon request.

TL431CZT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Package/Case:: TO-226-2, TO-92-2 (TO-226AC)

Series:: -

Packaging:: Tape & Reel (TR)

Product Status:: Active

Reference Type:: Shunt

Output Type:: Adjustable

Voltage - Output (Min/Fixed):: 2.495V

Voltage - Output (Max):: 36 V

Current - Output:: 100 mA

Tolerance:: ±2.21%

Temperature Coefficient:: -

Noise - 0.1Hz to 10Hz:: -

Noise - 10Hz to 10kHz:: -

Voltage - Input:: -

Current - Supply:: -

Current - Cathode:: 1 mA

Operating Temperature:: 0°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

TL431CZT FAQ

1.How can I place an order for TL431CZT through Aetrix?

Please submit a Request for Quotation (RFQ) for TL431CZT on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for TL431CZT reliable?

The price and inventory of TL431CZT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TL431CZT is usually 5 days.

3.What payment methods are accepted for TL431CZT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TL431CZT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TL431CZT?

TL431CZT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TL431CZT order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for TL431CZT?

For technical support, including TL431CZT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TL431CZT requirements.

6.How does Aetrix verify that TL431CZT is sourced from the original manufacturer or authorized distributors?

All TL431CZT products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that TL431CZT meets industry standards.

7.What is the process for return or replacement of TL431CZT?

All TL431CZT units undergo pre-shipment inspection (PSI). If there is an issue with TL431CZT, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The TL431CZT part is unused and in its original packaging.

Return procedure for TL431CZT:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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