LM431 IC Pin Configuration, Working and Its Applications

The IC LM431 is a three terminal regulator, and the main feature of this IC is a changeable output voltage, and the temperature strength is guaranteed above the whole temperature range of procedure. These integrated circuits are available in the package of chip-sized with the technology of national’s micro SMD. The output voltage of this IC is may be ranged from the above 2.5V to 36V only by choosing two exterior resistors that perform like a voltage separated network. Due to the quickly activate characteristics, this IC is an outstanding alternative for several applications of Zener diode. The similar components of this IC mainly include LM432, NJM2821, ZXRE060. NJM2822, NJM2820, This article discusses an overview of IC LM 431.

LM431 IC Pin Configuration

The IC LM431 includes three pins, and the function of each pin is discussed below.

  • Pin1 (Cathode): This is shunt current or o/p voltage
  • Pin2 (Reference): This pin is for adjustable o/p voltage
  • Pin3 (Anode): This pin is normally grounded
LM431 IC
LM431 IC

LM431 IC Features

The features of IC Lm431 include the following.

  • Output noise is low
  • The output voltage is programmable
  • The maximum voltages of reference, as well as the cathode, are – 0.5V & 37 V
  • Activate response is quick
  • Output impedance is low active
  • Highest reference i/p current is 10mA
  • The temperature range which is in use ranges from 0ºC- to -70ºC
  • Accessible in space reduction SOIC-8, TO-92, and SOT-23 packages
  • The average temperature coefficient is 50 ppm/°C
  • Highest dissipation of power is 0.78W
  • Highest constant cathode current is 150mA

LM431 IC based Crowbar Circuit Diagram

The main function of the crowbar circuit is to prevent the circuit from the overvoltage power supply condition. The can be functioned by connecting a short circuit otherwise low resistance lane across the output voltage. The designing of this circuit can be done by employing LM431 IC (adjustable zener regulator), TRIAC, Fuse, thyratron tube as the shorting apparatus etc.

Once activated, they can be rest on the current preventing power supply circuitry otherwise, if that stops working, the line fuse blowing otherwise circuit breaker tripping. The crowbar circuit is shown above. This specific circuit can be built with an LM431 IC for controlling the gate terminal of the TRIAC. The resistors used in the circuit are R1 & R2, and the divider of these can supply the reference voltage to the IC LM431.

Crowbar Circuit using LM431 IC
Crowbar Circuit using LM431 IC

The divider is located so that throughout common operating situations, the voltage across the second resistor is somewhat lesser than Vref of the IC. Because this voltage is less the smallest Vref of the IC, and a very small current is carried out through the IC.  If the voltage supply enhances, the voltage at the secondary resistor will go above Vref & the IC cathode will start to draw current.

If the supply voltage increases, the voltage across R2 will go above VREF and the LM431 cathode will begin to draw current. The gate terminal voltage will be dragged down, surpassing the gate terminal voltage of the TRIAC. This circuit is separate from a clamp in dragging, once activated, the voltage under the trigger level, frequently close to GND. A clamp stops the voltage from surpassing a fixed level. Therefore, a crowbar circuit will not routinely come back to usual process as the overvoltage condition is detached; power should be detached completely to end its conduction.

A crowbar can eliminate the short circuit while the transient is ended therefore letting the device to restart the usual process. The circuit uses a transistor, GTO (gate turn off) thyristor to short the circuit. These are frequently used to guard the frequency converter within the rotor circuit against current transients as well as high voltage occurred with the voltage dips inside the power network. Therefore the generator can travel during the error & quickly maintain the process even throughout the voltage dip.

The benefit of a crowbar circuit compares with a clamp is the low voltage of the crowbar allows carrying high error current without dissolving much power. As well, a crowbar circuit is more than a clamp for deactivating a device by driving a fuse, getting attention toward the defective apparatus.

Applications of LM431 IC

The LM431 IC can be used in several circuit applications; some of them include the following.

  • This IC can be used for designing a circuit with a constant current source
  • By connecting extra transistor as well as resistors to this IC, it can be used to design high-power regulator.
  • By connecting extra resistors to this IC, it can be used to design low-power shunt regulator.
  • This IC can be used to replace the Zener diode
  • This IC can be used as voltage regulators
  • It is used in monitoring the voltage
  • It can be used in sink circuits as well as current sources
  • It can be used for switching power supplies, current linear or adjustable voltage

Thus, this is all about LM431 IC pin configuration, features, the circuit with working and its applications. This IC is available for space critical applications for space saving in the packages of SOIC8, SOT23 & TO92. The least current used in this IC is 1 mA whereas the highest current used in this IC is 100 mA.

This IC is most frequently worked in the mode of the closed loop, wherever the reference node is fixed toward the o/p voltage through a resistor divider, the voltage can remains during regulation as long as the least current is among 1 mA &100 mA. Here is a question for you, what is the output voltage of LM431 IC?