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Sep 18 2020

Overview of TL431 Adjustable Shunt Regulator

Description

TL431 is a 2.5~36V adjustable precision shunt regulator. With its excellent performance and low price, it can be widely used in single-chip precision switching power supplies or precision linear regulated power supplies. In addition, TL431 can also form a voltage comparator, power supply voltage monitor, delay circuit, precision constant current source, etc.

This Video Introduced  TL431 Shunt Regulator Power Supply Circuits


Catalog

Description

Documents and Media

TL431 Pinout

TL431 Parameters

Features

Application

Package and Pins

Advantage

Working Principle

Functional Block Diagram

What is the Use of TL431?

What is TL431 Transistor?

Application Circuit

Product Manufacturer

FAQ


Documents and Media

Component Datasheet TL431 Datasheet
Selection guides 431 Device Nomenclature (Rev. B)
Application notes 1
Designing With the Improved TL431LI (Rev. A)
Application notes 2 TL431 Pin FMEA

TL431 Pinout

tl431 pinout tl431 pinout
tl431 pinout tl431 pinout
tl431 pinout tl431 pinout
tl431 pinout tl431 pinout

tl431 pin function


TL431 Parameters

Initial accuracy (Max) (%)

0.5, 1, 2

Iout/Iz (Max) (mA)

100

Iz for regulation (Min) (uA)

400

Operating temperature range (C)

-40 to 85, -40 to 125, 0 to 70

Rating

Catalog

Reference voltage

Adjustable

Temp coeff (Max) (ppm/ degree C)

92

VO (V)

2.495

VO adj (Max) (V)

36

VO adj (Min) (V)

2.495


Features

  • Reference Voltage Tolerance at 25°C
    • 0.5% (B Grade)
    • 1% (A Grade)
    • 2% (Standard Grade)
  • Adjustable Output Voltage: Vref to 36 V
  • Operation From −40°C to 125°C
  • Typical Temperature Drift (TL43xB)
    • 6 mV (C Temp)
    • 14 mV (I Temp, Q Temp)
  • Low Output Noise
  • 0.2-Ω Typical Output Impedance
  • Sink-Current Capability: 1 mA to 100 mA

Application

  • Switch mode Power supplies
  • Isolated Power supply circuits
  • Voltage comparators
  • Current Regulation circuits

Package and Pins

Package Pins Size

PDIP (P)

8

93 mm² 9.81 x 9.43

SOIC (D)

8

19 mm² 4.9 x 3.9

SOIC (D)

8

19 mm² 3.91 x 4.9

SOP (PS)

8

48 mm² 6.2 x 7.8

SOT-23 (DBV)

5

5 mm² 2.9 x 1.6

SOT-23 (DBZ)

3

7 mm² 2.92 x 2.37

SOT-89 (PK)

3

18 mm² 4.5 x 4.095

SOT-SC70 (DCK)

6

4 mm² 2 x 2.1

TO-92 (LP)

3

19 mm² 5.2 x 3.68

TSSOP (PW)

8

19 mm² 3 x 6.4


Advantage

The TL431 device is three-terminal adjustable shunt regulators, with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors. The device has a typical output impedance of 0.2 Ω. Active output circuitry provides a very sharp turn-on characteristic, making these devices excellent replacements for Zener diodes in many applications, such as onboard regulation, adjustable power supplies, and switching power supplies. The TL431 is offered in three grades, with initial tolerances (at 25°C) of 0.5%, 1%, and 2%, for the B, A, and standard grade, respectively. In addition, low output drift versus temperature ensures good stability over the entire temperature range.


Working Principle

When the input voltage increases, the output voltage increases, resulting in an increase in output sampling
Big. At this time, the internal circuit is adjusted to increase the current flowing through itself. This also increases the current flowing through the current limiting resistor. In this way, the voltage drop of the current limiting resistor increases, and the output voltage is equal to the input voltage minus the voltage drop of the current limiting resistor. At the same time, the increase of the input voltage and the increase of the voltage drop of the current-limiting resistor make the output voltage decrease and realize voltage stabilization.


Functional Block Diagram

  tl431 circuit

Vref is an internal 2.5V reference source, connected to the reverse input of the op amp. It can be seen from the characteristics of the op amp that only when the voltage at the REF terminal (the same direction terminal) is higher than Vref (2.5V), current will flow in the transistor. When the non-inverting input voltage is less than 2.5V, the triode is in the cut-off state (in an ideal state), and the current through the triode will change from 1mA to 100mA with the slight change of the REF terminal voltage. Of course, this diagram is by no means the actual internal structure of TL431, but it can be used to analyze and understand the circuit.

  tl431 circuit


What is the Use of TL431?

The TL431 is a reference voltage source that is commonly used in the control circuit of isolated power supplies. Typically used to provide a precision reference voltage, the TL431 can also be configured as an analog controller by exploiting its on-board error amplifier.


What is TL431 Transistor?

The TL431 is a regulator diode whose output voltage can be programmed by changing the value of resistors connected to it. It acts almost like a Zener diode except for that the voltage rating of this IC is programmable. It is commonly used to provide negative or positive voltage references.


Application Circuit

  • Precision High- Current Series Regulator

  • Output Control of a Three-Terminal Fixed Regulator

  • High-Current Shunt Regulator

Product Manufacturer

Texas Instruments Inc. (TI)  is an American technology company that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. Its headquarters are in Dallas, Texas, United States. TI is one of the top ten semiconductor companies worldwide, based on sales volume. Texas Instruments's focus is on developing analog chips and embedded processors, which accounts for more than 80% of their revenue. TI also produces TI digital light processing (DLP) technology and education technology products including calculators, microcontrollers and multi-core processors. To date, TI has more than 43,000 patents worldwide.


FAQ

  • What is the use of tl431?

The TL431 is a "programmable precision reference" and is commonly used in switching power supplies, where it provides feedback indicating if the output voltage is too high or too low. By using a special circuit called a bandgap, the TL431 provides a stable voltage reference across a wide temperature range.

  • What is tl431 transistor?

The TL431 is a regulator diode whose output voltage can be programmed by changing the value of resistors connected to it. It acts almost like a Zener diode except for that the voltage rating of this IC is programmable. It is commonly used to provide negative or positive voltage references.

  • How does a shunt regulator work?

The shunt regulator or shunt voltage regulator is a form of voltage regulator where the regulating element shunts the current to ground. The shunt regulator operates by maintaining a constant voltage across its terminals and it takes up the surplus current to maintain the voltage across the load.

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