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

STMicroelectronics TL1431CDT

Name: TL1431CDT
Brand: STMicroelectronics
SKU: TL1431CDT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: TL1431CDT

Manufacturer:: STMicroelectronics

Category:: Voltage Reference

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: TL1431CDT.pdf

Description:: IC VREF SHUNT ADJ 0.4% 8SO

Quantity:: RFQ Add To RFQ list

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Inventory:7,904

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Product details

Overview

TL1431CDT from STMicroelectronics is an adjustable shunt voltage reference IC with 0.4% initial voltage precision, 2.5 V to 36 V programmable output via two external resistors, and guaranteed operation from –20 °C to +70 °C. It delivers 1–100 mA sink current with 0.22 Ω typical dynamic impedance and supports precision feedback in isolated DC-DC converters.

For engineers reviewing the TL1431CDT datasheet, TL1431CDT pinout, TL1431CDT application, or TL1431CDT equivalent, key selection criteria include temperature-stable reference voltage (±3 mV over 0–70 °C), low dynamic impedance for loop stability, SO-8 batwing package thermal performance (R_thJA = 85 °C/W), and compatibility with optocoupler-based secondary-side regulation.

Technical Context

The TL1431CDT implements a bandgap-referenced error amplifier with internal 2.5 V reference, enabling precise voltage regulation through external resistor dividers. Its cathode-anode architecture functions as a programmable shunt regulator, where the REF pin senses the divided output and adjusts cathode current to maintain setpoint.

It operates across a wide cathode current range (1–100 mA) while maintaining ≤0.5 Ω max dynamic impedance up to 1 kHz and exhibits ±13 ppm/°C max temperature coefficient. The device requires no external compensation for capacitive loads ≤10 µF and supports stable operation with 15 kΩ/8.25 kΩ feedback networks per test circuit Figure 9.

Key Specifications

Parameter	Value and Actual Design Meaning
Reference Voltage	2.500 V (typical); sets minimum programmable output at 2.5 V with zero external divider resistance
Voltage Precision	±0.4% (max); ensures output accuracy within ±14.4 mV at 36 V setting over initial calibration
Temp Range	–20 °C to +70 °C; validated for commercial-grade power supply feedback loops without derating
Sink Current	1–100 mA; supports direct drive of optocoupler LEDs or parallel regulation with external transistors
Dynamic Impedance	0.22 Ω (typ), ≤0.5 Ω (max); maintains tight regulation under fast load transients in SMPS feedback paths
Ref Input Current	1.5–3.0 µA; enables high-impedance resistor dividers (e.g., 100 kΩ/10 kΩ) without significant error
Thermal Resistance	R_thJA = 85 °C/W (SO-8); allows 960 mW max power dissipation at 25 °C ambient before junction exceeds 150 °C

Pinout & Package

TL1431CDT uses the SO-8 batwing plastic micropackage (8-pin, 5.0 mm × 6.0 mm body, 1.27 mm pitch), optimized for thermal performance and automated assembly. Pin 1 is Cathode, Pin 2 is Anode, Pin 3 is REF, Pins 4–8 are NC (no connect) per Figure 2.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Cathode)	Current sink output	Connects to primary-side controller feedback node or optocoupler anode; carries full regulated current
Pin 2 (Anode)	Return path	Connected to system ground or negative rail; completes shunt current path
Pin 3 (REF)	Reference input	Senses voltage divider output; internal 2.5 V comparator triggers regulation when input ≥2.5 V
Pins 4–8	No Connect	Unused terminals; must remain unconnected to avoid parasitic coupling or thermal imbalance

Key Features

Feature	Design Value
Adjustable output range	2.5 V to 36 V via two-resistor divider - enables single BOM for multiple output voltages in multi-rail supplies
Low dynamic impedance	0.22 Ω typical - minimizes output voltage deviation during 100 mA load steps, critical for <1% regulation error
High temp stability	±3 mV max ΔV_REF over –20 to +70 °C - eliminates need for external trimming in industrial power modules
Low reference current	2.5 µA typical - permits use of >1 MΩ total divider resistance, reducing standby power in battery-backed systems
ESD robustness	2000 V HBM - withstands handling in standard manufacturing environments without special precautions

Applications

Isolated Flyback Converter

Programmable Linear Regulator

Use Scenario: Secondary-side voltage sensing in 12 V/3 A offline flyback supply with optocoupler 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 0.22 Ω impedance minimizing transient droop during 2 A step loads.

Use Scenario: Adjustable 5–24 V bench power supply using LM317 pass transistor and external current limit.

IC Role / Device Role / Timing Role: Precision 2.5 V reference for LM317 ADJ pin, replacing internal 1.25 V reference to extend output range and improve accuracy.

Use Value: Achieves 0.4% initial accuracy and ±3 mV temp drift vs. LM317's ±2% and ±100 ppm/°C, improving lab supply stability.

Overvoltage Protection Circuit

Current Sink Monitor

Use Scenario: 28 V avionics bus overvoltage clamp protecting downstream 24 V loads.

IC Role / Device Role / Timing Role: Programmable shunt element triggered at 28.5 V via resistor divider, sinking excess current to prevent rail collapse.

Use Value: 100 mA sink capability and 36 V max VKA rating allow direct clamping without series transistor, reducing component count and failure points.

Use Scenario: Real-time monitoring of 4–20 mA loop current in industrial sensor interface.

IC Role / Device Role / Timing Role: Fixed 2.5 V reference generating known voltage drop across precision sense resistor to derive current value.

Use Value: 2.5 µA REF current introduces <0.01% error in 250 Ω sense resistor measurement, meeting IEC 61000-4-5 immunity requirements.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TL431ACDT	0.25% initial precision, same SO-8 package and pinout	Higher accuracy required in medical power supplies where ±0.25% output tolerance is mandated	Select when tighter initial voltage tolerance justifies cost premium; identical layout and thermal behavior
LM4040CIM3-ADJ	Fixed 2.5 V output only; SOT-23-3 package; 100 µA max sink current	Used in low-power microcontroller ADC references where adjustable output is unnecessary	Choose only for non-adjustable, low-current (<1 mA) applications; not a functional replacement for TL1431CDT's 100 mA sink capability

Compared with TL431ACDT, TL1431CDT trades 0.15% precision for broader commercial temperature range (–20 to +70 °C vs. –40 to +85 °C) and lower cost; versus LM4040CIM3-ADJ, it provides 100× higher sink current and full adjustability but requires external resistors and larger SO-8 footprint.

Availability

TL1431CDT is available at Aetrix Electronics and suitable for isolated DC-DC converters, programmable linear regulators, and overvoltage protection circuits requiring stable component supply and long-term manufacturability.

Supply support for TL1431CDT 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, MCU, power, and sensor solutions for automotive, industrial, and consumer markets.

The TL1431 belongs to ST's precision analog voltage reference product line, engineered specifically for high-stability feedback in switch-mode power supplies and industrial control systems where accuracy, thermal drift, and sink current capability are critical.

FAQ

What is the minimum cathode current required for regulation in TL1431CDT?

The TL1431CDT requires a minimum cathode current of 0.5 mA (typical) to maintain regulation, as specified in Table 4. Below this threshold, the device exits active regulation mode and output voltage rises uncontrollably. This value is verified at 25 °C and remains ≤1.0 mA across the full –20 °C to +70 °C operating range.

Can TL1431CDT replace TL431 in existing designs?

Yes, TL1431CDT is pin-compatible and functionally equivalent to TL431 in SO-8 packages, sharing identical pinout (Cathode-Anode-REF), electrical specs (2.5 V reference, 1–100 mA sink), and thermal characteristics. No layout or firmware changes are needed, though final validation under worst-case temperature and load conditions is recommended.

How does the SO-8 batwing package improve thermal performance?

The SO-8 batwing package features extended lead frames that increase copper surface area for heat conduction, achieving R_thJA = 85 °C/W - 35% lower than standard SO-8. This allows 960 mW maximum power dissipation at 25 °C ambient, supporting higher continuous cathode currents without heatsinking in compact power supply designs.

What is the role of the NC pins (4–8) in TL1431CDT?

Pins 4–8 are internally unconnected and serve no electrical function. They must remain floating - no routing, grounding, or capacitive loading - to prevent parasitic coupling into the sensitive REF node or thermal imbalance affecting junction temperature measurement. ST confirms these pins are die-bonded but not wire-bonded in the SO-8 batwing variant.

TL1431CDT Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Package/Case:: 8-SOIC (0.154", 3.90mm Width)

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:: ±0.4%

Temperature Coefficient:: 90ppm/°C

Noise - 0.1Hz to 10Hz:: -

Noise - 10Hz to 10kHz:: -

Voltage - Input:: -

Current - Supply:: -

Current - Cathode:: 1 mA

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-SOIC

TL1431CDT FAQ

1.How can I place an order for TL1431CDT through Aetrix?

Please submit a Request for Quotation (RFQ) for TL1431CDT 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 TL1431CDT reliable?

The price and inventory of TL1431CDT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TL1431CDT is usually 5 days.

3.What payment methods are accepted for TL1431CDT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TL1431CDT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for TL1431CDT?

TL1431CDT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your TL1431CDT 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 TL1431CDT?

For technical support, including TL1431CDT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TL1431CDT requirements.

6.How does Aetrix verify that TL1431CDT is sourced from the original manufacturer or authorized distributors?

All TL1431CDT 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 TL1431CDT meets industry standards.

7.What is the process for return or replacement of TL1431CDT?

All TL1431CDT units undergo pre-shipment inspection (PSI). If there is an issue with TL1431CDT, 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 TL1431CDT part is unused and in its original packaging.

Return procedure for TL1431CDT:

1.Submit a request within 90 days.

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

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