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

    AAC Fanatic!

    Jun 22, 2012
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    928
    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
    678
    14
    Thank you.

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

    AAC Fanatic!

    Jun 22, 2012
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    928
    no,
    12.9v
     
  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
    678
    14
    Thank you I don't know where I got the 11.4 Volts from. :confused:
     
  6. ian field

    AAC Fanatic!

    Oct 27, 2012
    5,120
    908
    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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