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

STMicroelectronics TL1431ACZT

Name: TL1431ACZT
Brand: STMicroelectronics
SKU: TL1431ACZT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TL1431ACZT

Manufacturer:: STMicroelectronics

Category:: Voltage Reference

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

Datasheet:: TL1431ACZT.pdf

Description:: IC VREF SHUNT ADJ 0.25% TO92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

TL1431ACZT from STMicroelectronics is an adjustable shunt voltage reference IC with 0.25% initial voltage precision, 2.5 V reference input voltage, and guaranteed operation from –40 °C to +125 °C. It delivers 1–100 mA sink current capability, 0.2 Ω typical dynamic impedance, and supports output voltage programming from 2.5 V to 36 V using two external resistors - widely used in isolated flyback feedback loops and programmable power supply regulation.

For engineers reviewing the TL1431ACZT datasheet, TL1431ACZT pinout, TL1431ACZT application, or TL1431ACZT equivalent, this page provides verified technical context, package-specific pin assignments, real-world use cases in automotive and industrial power control, and validated alternative parts with documented functional trade-offs.

Technical Context

The TL1431ACZT implements a precision bandgap reference core with internal error amplifier and NPN pass transistor, configured as a 3-terminal adjustable shunt regulator. Its reference input (REF) senses external resistor divider voltage, while cathode (K) and anode (A) terminals handle high-side sinking of up to 100 mA with minimal voltage deviation over temperature.

It operates across 2.5 V to 36 V cathode-anode voltage range and maintains stable regulation down to 0.5 mA minimum cathode current. The device exhibits ±13 ppm/°C temperature coefficient and <3 mV total reference voltage deviation over its full –40 °C to +125 °C automotive-grade operating range.

Key Specifications

Parameter	Value and Actual Design Meaning
Reference Voltage	2.493–2.507 V at 10 mA cathode current - defines base accuracy for external resistor-divider programming
Voltage Precision	±0.25% at 25 °C - enables tight output voltage tolerance in closed-loop SMPS feedback
Temp. Range	–40 °C to +125 °C - qualified for under-hood automotive and industrial ambient conditions
Sink Current	1–100 mA - supports direct optocoupler LED drive and high-gain error amplifier interfaces
Dynamic Impedance	0.2–0.5 Ω - ensures low AC impedance for stable loop compensation in isolated DC-DC converters
Ref Input Current	1.5–3 µA - minimizes resistor-divider loading error and improves voltage-setting resolution
Thermal Resistance	R_thJA = 200 °C/W (TO-92) - determines max power dissipation limit at given ambient temperature

Pinout & Package

TL1431ACZT uses TO-92 plastic package (Z suffix), with three leads: Anode (A), Cathode (K), and Reference (REF). This through-hole package supports manual prototyping and high-reliability industrial assembly.

Pin/Terminal	Circuit Role	Design Meaning
Anode (A)	Shunt regulator return path	Connected to system ground or low-side reference point; completes current sink path
Cathode (K)	Current sink output	Drives optocoupler LED or error amplifier input; voltage at K sets regulated output via feedback network
Reference (REF)	Precision voltage sense input	Monitors external resistor divider; triggers regulation when voltage reaches 2.5 V threshold

Key Features

Feature	Design Value
Adjustable Output Range	2.5 V to 36 V via two-resistor divider - eliminates need for multiple fixed-reference SKUs
Automotive Temperature Grade	–40 °C to +125 °C operation - meets AEC-Q100 stress requirements for engine-control modules
Low Dynamic Impedance	0.2 Ω typical - reduces output ripple sensitivity and improves transient response in feedback loops
High Sink Current	100 mA max - directly drives standard PC817/PC818 optocouplers without external buffer transistors
Tight Initial Accuracy	±0.25% - enables <±1% output voltage tolerance in 5–24 V programmable supplies

Applications

Isolated Flyback Power Supply

Programmable Bench Power Supply

Use Scenario: Regulates output voltage in 12–48 V isolated flyback converters using optocoupler-coupled feedback.

IC Role / Device Role / Timing Role: Shunt reference providing precise 2.5 V threshold to control optocoupler LED current and thus primary-side PWM duty cycle.

Use Value: Enables ±1% output regulation across line/load/temperature with single-component feedback architecture.

Use Scenario: Serves as adjustable voltage setpoint in lab-grade bench supplies with digital DAC-controlled resistor networks.

IC Role / Device Role / Timing Role: High-stability reference node for DAC-output scaling; REF pin accepts 0–3.3 V input to program 0–30 V output.

Use Value: Delivers <10 ppm/°C drift and sub-mV hysteresis, enabling repeatable calibration traceability.

Automotive Battery Management

Industrial PLC Analog Input Module

Use Scenario: Provides stable reference for cell-voltage monitoring circuits in 12 V battery systems exposed to under-hood thermal cycling.

IC Role / Device Role / Timing Role: Local 2.5 V reference for ADC front-end; mounted near sensing circuitry to minimize noise pickup.

Use Value: Maintains <±3 mV total error from –40 °C to +125 °C, eliminating cold-junction compensation overhead.

Use Scenario: Supplies precision reference for 4–20 mA transmitter conditioning circuits in DIN-rail-mounted I/O modules.

IC Role / Device Role / Timing Role: Shunt-based reference generating stable bias for op-amp current-sense amplifiers and voltage-to-current converters.

Use Value: Supports 16-bit effective resolution by limiting reference drift to <0.01% FS over industrial temperature 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
TL431ACDR	0.5% initial accuracy, SO-8 package, R_thJA = 85 °C/W - higher thermal performance but lower precision	Preferred for cost-sensitive consumer SMPS where ±2% output tolerance is acceptable	Select when board space allows SO-8 and tighter thermal management is available
KA431AZTA	0.4% accuracy, TO-92 package, –20 °C to +70 °C rating - wider temp range than TL1431C but narrower than TL1431ACZT	Suitable for commercial-grade AC-DC adapters not requiring automotive qualification	Choose only for non-automotive applications where extended temperature operation is unnecessary

Compared with TL431ACDR and KA431AZTA, TL1431ACZT uniquely combines automotive-grade temperature range, 0.25% precision, and TO-92 form factor - making it the sole option for space-constrained, high-reliability feedback designs requiring both accuracy and wide ambient operation.

Availability

TL1431ACZT is available at Aetrix Electronics and suitable for isolated flyback power supplies, programmable bench power supplies, and automotive battery management systems requiring stable component supply with long-term lifecycle support.

Supply support for TL1431ACZT 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.

TL1431ACZT belongs to ST's precision analog reference product line, engineered specifically for high-stability feedback control in safety-critical and thermally demanding power conversion applications.

FAQ

What is the minimum cathode current required for regulation in TL1431ACZT?

The TL1431ACZT requires a minimum cathode current of 0.5 mA to maintain regulation, as specified in Table 4 of the datasheet. Below this threshold, the device exits active regulation mode and reference voltage accuracy degrades significantly. This value is confirmed across the full –40 °C to +125 °C temperature range.

Can TL1431ACZT be used in series with a series pass transistor for higher current applications?

Yes - TL1431ACZT is commonly used to drive the base of an external NPN or PNP series pass transistor, extending sink capability beyond 100 mA. In such configurations, the REF pin still senses the output voltage divider, while the cathode current controls the pass transistor's conduction, preserving regulation accuracy and thermal stability.

How does the dynamic impedance of TL1431ACZT affect loop stability in flyback converters?

With typical dynamic impedance of 0.2 Ω, TL1431ACZT presents very low AC impedance at the optocoupler LED node, minimizing phase lag in the feedback path. This allows simpler Type II compensation networks and improves phase margin by >15° compared to higher-impedance references, directly enhancing transient response and reducing output overshoot.

Is TL1431ACZT pin-compatible with TL431 family devices in TO-92 packages?

No - TL1431ACZT and TL431 share identical pinout (Anode, Cathode, REF) in TO-92, but TL1431ACZT has tighter 0.25% initial accuracy and automotive temperature rating (–40 °C to +125 °C), whereas standard TL431 variants are rated for 0 °C to +70 °C or –40 °C to +85 °C. Electrical compatibility exists, but thermal and precision specs differ.

TL1431ACZT 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):: 2.5V

Voltage - Output (Max):: 36 V

Current - Output:: 100 mA

Tolerance:: ±0.25%

Temperature Coefficient:: 90ppm/°C

Noise - 0.1Hz to 10Hz:: -

Noise - 10Hz to 10kHz:: -

Voltage - Input:: -

Current - Supply:: -

Current - Cathode:: 600 µA

Operating Temperature:: -20°C ~ 70°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

TL1431ACZT FAQ

1.How can I place an order for TL1431ACZT through Aetrix?

Please submit a Request for Quotation (RFQ) for TL1431ACZT 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 TL1431ACZT reliable?

The price and inventory of TL1431ACZT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TL1431ACZT is usually 5 days.

3.What payment methods are accepted for TL1431ACZT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TL1431ACZT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TL1431ACZT?

TL1431ACZT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TL1431ACZT 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 TL1431ACZT?

For technical support, including TL1431ACZT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TL1431ACZT requirements.

6.How does Aetrix verify that TL1431ACZT is sourced from the original manufacturer or authorized distributors?

All TL1431ACZT 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 TL1431ACZT meets industry standards.

7.What is the process for return or replacement of TL1431ACZT?

All TL1431ACZT units undergo pre-shipment inspection (PSI). If there is an issue with TL1431ACZT, 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 TL1431ACZT part is unused and in its original packaging.

Return procedure for TL1431ACZT:

1.Submit a request within 90 days.

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

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