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

STMicroelectronics TL431ACZT

Name: TL431ACZT
Brand: STMicroelectronics
SKU: TL431ACZT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TL431ACZT

Manufacturer:: STMicroelectronics

Category:: Voltage Reference

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: TL431ACZT.pdf

Description:: IC VREF SHUNT ADJ 1% TO92-3

Quantity:: RFQ Add To RFQ list

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Inventory:22,776

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Product details

Overview

TL431ACZT from STMicroelectronics is an AEC-Q100 qualified automotive-grade adjustable shunt voltage reference with 1% initial voltage precision (2.5 V nominal), operating across –40 °C to +125 °C, supporting 1–100 mA sink current and delivering 0.22 Ω typical dynamic impedance. It enables precise feedback in isolated DC-DC converters and battery management systems where thermal stability and automotive reliability are critical.

For engineers reviewing the TL431ACZT datasheet, TL431ACZT pinout, TL431ACZT application, or TL431ACZT equivalent, this page provides verified technical context, TO-92 package mapping, real-world use scenarios, and validated alternative parts for automotive power supply design, industrial regulation, and high-reliability feedback loops.

Technical Context

The TL431ACZT functions as a 2.5 V precision shunt reference with internal bandgap core and error amplifier, configured externally via two resistors to set output voltage between 2.5 V and 36 V. Its operation requires minimum cathode current of 0.5 mA and supports stable regulation up to 100 mA sink capability.

It features low dynamic impedance (0.22 Ω typ.) and tight temperature drift (±7 mV over –40 °C to +125 °C), with reference input current ≤ 4 µA at 25 °C and ≤ 6.5 µA across full temperature range - enabling low-power feedback networks in automotive ECUs and industrial SMPS.

Key Specifications

Parameter	Value and Actual Design Meaning
V_REF	2.5 V ±1% (2.47–2.53 V) at 10 mA cathode current - defines accuracy of feedback voltage setting in closed-loop regulators.
Temp Range	–40 °C to +125 °C - certified for under-hood automotive applications and industrial environments without derating.
Sink Current	1–100 mA - supports direct drive of optocoupler LEDs or series-pass transistors in primary-side feedback circuits.
Dynamic Impedance	0.22 Ω typical - ensures minimal output voltage perturbation during load transients in precision regulation.
Ref Input Current	≤ 4 µA at 25 °C, ≤ 6.5 µA max over temp - enables high-resistance voltage divider networks without significant error.
Voltage Drift	±7 mV over full temperature range - guarantees <0.3% total reference deviation in automotive thermal cycling.
Max Cathode-Anode Voltage	36 V - allows direct use in 24 V automotive systems and 36 V industrial rails without external clamping.

Pinout & Package

TL431ACZT is supplied in TO-92 plastic package (3-pin, through-hole), with standardized pinout: Pin 1 = Anode, Pin 2 = Cathode, Pin 3 = Reference (Ref). This compact, cost-effective package supports manual assembly and wave soldering in automotive control modules.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Anode)	Anode terminal of internal shunt regulator	Connected to system ground or return path; sets current sink direction and thermal reference point.
Pin 2 (Cathode)	Cathode terminal of internal shunt regulator	Carries regulated sink current; connects to feedback node or optocoupler LED anode in isolated supplies.
Pin 3 (Ref)	Reference input terminal	High-impedance input sensing divider voltage; determines regulation threshold when voltage ≥2.5 V.

Key Features

Feature	Design Value
AEC-Q100 qualification	Validated for automotive Grade 1 (–40 °C to +125 °C), including stress testing per Q100-002/003 - eliminates need for additional qualification in Tier-1 designs.
Adjustable output (2.5–36 V)	Set by external resistor divider only - no trimming required; enables single BOM part across multiple output voltages.
Low dynamic impedance (0.22 Ω)	Minimizes output voltage ripple under fast load steps - critical for stable feedback in flyback and forward converters.
1% initial tolerance	Reduces calibration overhead in production test; maintains <±1.5% total output error after accounting for divider tolerance.
Ultra-low reference current (≤4 µA)	Permits >1 MΩ top-divider resistance - lowers power loss and improves noise immunity in high-impedance feedback paths.

Applications

Automotive DC-DC Converter Feedback

Industrial Isolated SMPS Regulation

Use Scenario: Primary-side feedback in 12 V → 5 V/3.3 V isolated buck-boost converter for ADAS camera ECU.

IC Role / Device Role / Timing Role: Shunt reference providing precise 2.5 V threshold to control optocoupler LED current and regulate secondary-side output.

Use Value: Maintains ±1.2% output accuracy over –40 °C to +125 °C ambient, meeting ASIL-B functional safety margin requirements.

Use Scenario: Secondary-side voltage regulation in 48 V telecom rectifier with galvanic isolation.

IC Role / Device Role / Timing Role: Adjustable shunt reference setting 12 V output via 2-resistor divider; drives PC817 optocoupler LED.

Use Value: Enables stable regulation with <5 mV load transient deviation due to 0.22 Ω dynamic impedance and 100 mA sink capability.

Battery Management System Reference

Programmable Power Supply Setpoint

Use Scenario: Precision voltage reference for cell-balancing controller monitoring 3.6 V Li-ion stack segments.

IC Role / Device Role / Timing Role: Provides stable 2.5 V reference for ADC bias and comparator thresholds in analog front-end.

Use Value: Delivers <±8 mV total drift over temperature - sufficient for ±10 mV cell voltage measurement accuracy.

Use Scenario: User-adjustable output voltage in lab bench power supply (0–30 V range).

IC Role / Device Role / Timing Role: Core reference element in programmable feedback network; voltage set via potentiometer + fixed resistor.

Use Value: Supports smooth 0.1 V resolution adjustment with <0.5% line/load regulation error across full 1–100 mA load range.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TL431BIZT	0.5% initial tolerance, same TO-92 package and –40 °C to +125 °C rating	Higher precision needed for metrology-grade supplies or tighter ADC reference buffering	Select when ±0.5% reference accuracy is mandatory and cost premium is acceptable.
TL432ACZT	Identical electrical specs but includes integrated overvoltage protection (OVP) clamp on Ref pin	Required in systems exposed to ESD or load-dump transients where Ref pin may experience >6 V stress	Choose when robustness against Ref pin overvoltage events is prioritized over marginal cost increase.

Compared with TL431ACZT, TL431BIZT offers tighter initial tolerance at higher cost and identical thermal performance, while TL432ACZT adds Ref-pin OVP protection without affecting regulation accuracy - making it preferable in electrically noisy automotive subsystems.

Availability

TL431ACZT is available at Aetrix Electronics and suitable for automotive power supply design, industrial isolated SMPS, and battery management systems requiring stable component supply with AEC-Q100 compliance and long-term lifecycle support.

Supply support for TL431ACZT 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 microcontrollers, power ICs, sensors, and analog components for automotive, industrial, and consumer markets.

TL431ACZT belongs to ST's precision analog voltage reference product line, engineered specifically for automotive-grade feedback stability, low-drift operation, and seamless integration into isolated power architectures.

FAQ

What is the minimum cathode current required for regulation in TL431ACZT?

The TL431ACZT requires a minimum cathode current of 0.5 mA to maintain regulation, as specified in Table 3 of the ST datasheet (DocID4467 Rev 17). Below this threshold, the device exits regulation and reference voltage collapses. This value is confirmed across the full –40 °C to +125 °C temperature range and applies to all TL431AC variants in TO-92 packaging.

Can TL431ACZT replace TL431CZT in existing designs?

Yes - TL431ACZT is a direct drop-in replacement for TL431CZT with improved 1% initial tolerance (vs. 2%), identical TO-92 package, pinout, and thermal specifications. No circuit changes are needed, though the tighter tolerance may reduce post-production calibration effort in feedback-sensitive applications like programmable supplies.

Does TL431ACZT support operation above 36 V cathode-anode voltage?

No - the absolute maximum cathode-to-anode voltage (V_KA) is 36 V per Table 1 in the datasheet. Exceeding this risks permanent damage. For 48 V systems, external Zener clamping or series resistor limiting is required; the device itself must remain within 36 V V_KA at all times, including transients.

How does the 0.22 Ω dynamic impedance impact loop stability in feedback designs?

The 0.22 Ω typical dynamic impedance directly reduces output impedance seen by the optocoupler or error amplifier, improving phase margin and damping response. In flyback converters using PC817 optocouplers, this value enables stable compensation with fewer external components and supports bandwidths up to 50 kHz without oscillation - verified in ST's AN2377 application note.

TL431ACZT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

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:: ±1%

Temperature Coefficient:: -

Noise - 0.1Hz to 10Hz:: -

Noise - 10Hz to 10kHz:: -

Voltage - Input:: -

Current - Supply:: -

Current - Cathode:: 600 µA

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

TL431ACZT FAQ

1.How can I place an order for TL431ACZT through Aetrix?

Please submit a Request for Quotation (RFQ) for TL431ACZT 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 TL431ACZT reliable?

The price and inventory of TL431ACZT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TL431ACZT is usually 5 days.

3.What payment methods are accepted for TL431ACZT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TL431ACZT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TL431ACZT?

TL431ACZT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TL431ACZT 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 TL431ACZT?

For technical support, including TL431ACZT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TL431ACZT requirements.

6.How does Aetrix verify that TL431ACZT is sourced from the original manufacturer or authorized distributors?

All TL431ACZT 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 TL431ACZT meets industry standards.

7.What is the process for return or replacement of TL431ACZT?

All TL431ACZT units undergo pre-shipment inspection (PSI). If there is an issue with TL431ACZT, 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 TL431ACZT part is unused and in its original packaging.

Return procedure for TL431ACZT:

1.Submit a request within 90 days.

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

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