TL431 Test Circuit

Discussion in 'The Projects Forum' started by RodneyB, Aug 10, 2015.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I would like to build a test circuit to check if the TL431 in my circuit is faulty or not. I found this circuit when doing an internet search, however there was no description as to how it works.

    Is this circuit suitable and how does it work?

    Thanks
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    the voltage is set by the formula.

    10K/2.4K + 1 x 2.5v = set voltage

    with the values shown thats 12.9V
     
    Péter András likes this.
  3. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Thank you.

    Does this mean the LED will only come on at 11.4 Volts?
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    no,
    12.9v
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    633
    13
    Thank you I don't know where I got the 11.4 Volts from. :confused:
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    The simplest test is just connect Vin to cathode and it should behave like a 2.5V zener.

    It needs at least 1mA and the maximum current is 100mA - as long as you make sure it doesn't exceed the dissipation limit.

    Its actually a comparator with a built in 2.5V reference.
     
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