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TL431ACLP

Precision programmable shunt reference, 2.495V-36V, 0.5% accuracy, TO-92

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Manufacturer Part：

TL431ACLP

Package：

TO-92 (3-pin through-hole, 5.21 x 4.19mm)

Brand：

Product Categories：

Analog Linear ICs, Integrated Circuits ICs

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Description

Product Overview

The TL431ACLP is a precision programmable shunt voltage reference from Texas Instruments with 0.5% initial accuracy, 2.495V to 36V adjustable output, and 1mA to 100mA cathode current range in a TO-92 through-hole package.

Key Specifications

Reference Voltage (Vref)	2.495V typical (VKA = Vref)
Initial Accuracy (A-grade)	±0.5% at 25°C
Adjustable Output Range	Vref to 36V (2.495V to 36V)
Cathode Current Range	1mA to 100mA
Reference Input Current	2µA typical
Dynamic Impedance	0.2Ω typical
Temperature Stability	10mV typical over -40°C to +85°C
Supply Voltage (VKA max)	36V
Operating Temperature	0°C to +70°C (C-grade)
Package	TO-92 (3-pin through-hole)

Features

Precision 2.495V bandgap reference with ±0.5% accuracy
Output voltage adjustable from Vref to 36V via external resistors
Low dynamic output impedance: 0.2Ω typical
Wide operating cathode current range: 1mA to 100mA
Low reference input current: 2µA typical
Active output circuitry for sharp turn-on characteristics
Direct replacement for industry-standard TL431
Multiple grade options for accuracy and temperature range

Applications

Switching power supply feedback loops
Adjustable voltage references
Shunt regulators and voltage monitors
Constant current sources
Overvoltage and undervoltage protection

Product Introduction:TL431ACLP Product Introduction

The TL431ACLP is a three-terminal programmable shunt voltage reference from Texas Instruments that combines a precision 2.495V bandgap reference with an error amplifier and open-collector output transistor. The A-grade provides ±0.5% initial accuracy at 25°C. The output voltage can be programmed from Vref (2.495V) to 36V using an external resistor divider. The device sinks 1mA to 100mA cathode current with a low 0.2Ω dynamic output impedance, making it an effective shunt regulator. The C-grade is rated for commercial temperature range (0°C to +70°C). It is one of the most widely used voltage references in switching power supply feedback loops worldwide.

Working Principle:TL431ACLP Working Principle

The TL431ACLP integrates a temperature-compensated bandgap reference, error amplifier, and NPN output transistor in a three-terminal shunt configuration. The REF pin connects to the inverting input of the internal error amplifier, which compares the external voltage divider output with the 2.495V internal bandgap reference. When the voltage at REF exceeds Vref, the error amplifier drives the NPN output transistor to sink more cathode current, pulling the cathode voltage lower. When REF falls below Vref, the NPN turns off, allowing the cathode voltage to rise. This negative feedback loop regulates the output voltage at Vref × (1 + R1/R2) + Iref × R2, where Iref is the 2µA reference input current. For the simplest configuration with REF tied to CATHODE, the output is fixed at 2.495V. In a switching power supply, the TL431 is typically optocoupled to the primary side controller, with the REF pin monitoring the output voltage through a resistor divider. The low 0.2Ω dynamic impedance ensures the cathode voltage changes minimally with cathode current variations, providing tight regulation.

Pin Description:TL431ACLP Pin Definition and Functions

Pin	Name	Type	Description
1	REF	Input	Reference input (connect to output divider)
2	ANODE	Power	Anode (connect to GND)
3	CATHODE	Power/Output	Cathode (connect to supply via resistor, sinks 1-100mA)

Application Scenarios:In which products and applications isTL431ACLP used

SMPS Feedback: 0.5% accuracy and low dynamic impedance provide tight output voltage regulation in isolated flyback and forward converters
Adjustable References: External resistor divider sets any voltage from 2.495V to 36V for precision bias applications
Voltage Monitoring: REF pin threshold comparison enables overvoltage and undervoltage detection circuits
Shunt Regulation: 100mA sink capability provides effective shunt regulation for low-power supply rails
Constant Current: Configured with a sense resistor and NPN transistor, the TL431 creates a precision constant current source

Alternative Models:What chips are recommended as replacements for TL431ACLP

Model	Manufacturer	Key Difference	Package	Specs
KA431AZTA	onsemi	Direct compatible replacement with identical 2.495V reference and 1-100mA cathode current range	TO-92-3	2.495V/1-100mA
LM431ACM	TI	Direct equivalent in SOIC-8 surface-mount for compact power supply feedback loops	SOIC-8	2.495V/A-grade
TLV431ACDBZR	TI	Low-voltage 1.24V reference version with 80µA minimum cathode current for low-power designs	SOT-23-3	1.24V/80µA min
ATL431LIBQDBZR	TI	Ultra-low-power 25µA min cathode current version for battery-powered and standby circuits	SOT-23-3	2.5V/25µA min
LM4040C10IDBZR	TI	Fixed 10V precision shunt reference with 0.1% tolerance for high-accuracy voltage regulation	SOT-23-3	10V fixed/0.1%

TL431ACLP is an adjustable 2.495-36V shunt voltage regulator in TO-92-3 with ±1% A-grade reference tolerance and 1-100mA cathode current. The KA431 and LM431 are direct pin-compatible replacements. TLV431 offers a 1.24V low-voltage reference, while ATL431 provides ultra-low 25µA minimum cathode current for battery applications. LM4040 provides fixed-voltage precision references.