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TL431 VKA < Vref condition

K. Sasaki14
Guru 10200 points
Other Parts Discussed in Thread: TL431

Our customer's TL431 circuit is the following,

V1 rises up to about 6.8V. So REF pin voltage became 3.4V and Cathode voltage became 1.88V.
According to datasheet recommended operating condition, VKA range is Vref to 36V. 
VKA becomes lower than Vref in above circuit. This is out of range.

Is there any concern about this circuit? Is there possibility that TL431 is broken when VKA is lower than Vref?

Best Regards,
Kohei Sasaki

  • 0
    TI__Mastermind 24485 points
    Hello Sasaki-san,

    I am moving this to the Voltage References forum.

    Also, this is a standard, expected way of operating the TL431, and also an expected response. The TL431 is being used in a comparator type mode for this application, so when the reference voltage is > 2.5V, the Cathode will be pulled to about 2V, sinking current to ground.

    There is also some data provided in the last post of the following E2E thread if you are curious about the response under differing conditions:

    e2e.ti.com/.../1689982

    In short, there is no concern with this circuit and there is no possibility of damage to the TL431 in this application.

    Best,
    Michael