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TL431B: TL431B REF pin voltage and current range

Part Number: TL431B

Hi Team

     I have a question on TL431B Vref voltage and current limitation. 

     TL431B can be used as a comparator desicribed in datasheet. At comparator application, what's the voltage and current range of REF pin. we are reviewing customer's design. 

    Thanks. 

     Tiger 

  • Hi Tiger,

    The TL431B REF pin is characterized by the amount of current it requires. In a typical application when VREF = 2.495V, the current required is 4uA max. In open loop this value is still true but most of the time the voltage will be either higher or lower than the internal 2.495V band gap circuit.
    The current limitations on this pin are in the ABS max table of -0.05 mA to 10 mA.
    It is highly recommended when using the TL431 in comparator application to use a current limit resistor. This resistor will be in series such as Rin in section 10.2 of the datasheet. This resistor will not affect the accuracy of the trigger point by much but it will keep the device safe. I will recommend to keep the current into the REF pin below 1mA. To test the max current make sure the device is experiencing the worst case high voltage on VREF pin then size the Rin resistor appropriately.

    -Marcoo