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TL431ACDBZR

Prog shunt Vref, 2.495V, +/-0.5%, 1-100mA, SOT-23-3

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Manufacturer Part：

TL431ACDBZR

Package：

SOT-23-3 (2.90 x 1.30 x 1.00 mm)

Brand：

Product Categories：

Integrated Circuits ICs, Low Dropout Regulators (LDO)

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Description

Product Overview

The TL431ACDBZR from Texas Instruments is a precision programmable shunt voltage reference with 2.495V internal reference, +/-0.5% initial accuracy, and 1-100mA cathode current range in a SOT-23-3 package.

Key Specifications

Reference Voltage	2.495 V (internal, programmable to 36V)
Initial Accuracy	+/-0.5% (AC grade)
Temperature Drift	6 mV typ over -40 to +125°C
Cathode Current Range	1 mA to 100 mA
Reference Input Current	2 uA typical
Dynamic Impedance	0.2 Ohm typical
Output Voltage Range	Vref to 36 V (programmable)
Operating Temperature	-40°C to +125°C
Package	SOT-23-3

Features

Precision shunt reference with +/-0.5% accuracy and 0.2 Ohm dynamic impedance
Programmable output from 2.495V to 36V with only 2uA reference input current

Applications

SMPS feedback loop error amplifier and optocoupler driver
Precision voltage reference and comparator threshold generator

Product Introduction:TL431ACDBZR Product Introduction

The TL431ACDBZR from Texas Instruments is the industry-standard precision programmable shunt voltage reference in a tiny SOT-23-3 surface-mount package. The device consists of a 2.495V internal bandgap reference, error amplifier, and open-collector NPN output transistor in a three-terminal shunt regulator configuration. The AC grade provides +/-0.5% initial accuracy at 25°C. The output voltage is programmable from 2.495V to 36V using two external resistors. The very low 0.2 Ohm dynamic impedance ensures tight regulation under varying load conditions. The 1mA to 100mA cathode current range covers the full range from micropower biasing to direct optocoupler LED drive in SMPS feedback loops. The SOT-23-3 package is the smallest available for the TL431, ideal for space-constrained designs.

Working Principle:TL431ACDBZR Working Principle

The TL431ACDBZR operates as a three-terminal programmable shunt voltage regulator. (1) Internal Reference: A bandgap cell generates the internal 2.495V reference. The reference pin (REF) is connected to the non-inverting input of an internal error amplifier. (2) Shunt Regulation: The inverting input of the error amplifier is also connected to the REF pin through the internal reference. When the voltage at REF exceeds 2.495V, the error amplifier drives the NPN output transistor to sink more cathode current, pulling the cathode voltage lower. When REF is below 2.495V, the NPN is off and the cathode current is at minimum. (3) Programmable Output: External resistors R1 and R2 form a voltage divider from the cathode to ground, with the midpoint connected to REF. The output voltage is VOUT = Vref x (1 + R1/R2) + Iref x R1. Since Iref is only 2uA, the voltage is accurately set by the resistor ratio. (4) SMPS Feedback: In a typical SMPS application, the TL431 monitors the output voltage through a resistor divider. When the output rises above the setpoint, the TL431 cathode current increases, driving the optocoupler LED harder, which signals the primary-side PWM controller to reduce duty cycle.

Pin Description:TL431ACDBZR Pin Definition and Functions