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TPS24711: negative spike on VOUT pin

Given Ding
Genius 10125 points
Part Number: TPS24711

Hi Team, 

Customer do vout short test and found negative spike on VOUT pin is beyond our spec. Please kindly check if it's OK. 

Ch4=VOUT 

  • 0
    TI__Guru 57737 points

    Hi Given Ding,

    A Schottky diode has to be placed at the output of the Hotswap to make sure that the –ve voltage transient does not go beyond the Abs max rating of the Hotswap Controller.

    Selection Criteria for Schottky diode:

    Due to output inductance, there will be negative voltage spikes generated at output of Hotswap during transient conditions like fast turn off. We need to make sure that the –ve voltage generated at output should be clamped below |-0.3 V| which is generally the absmax rating of the Hotswap. The Schotty diode used at the output should have,

    • A DC blocking  voltage rating much higher than the Vinmax
    • Non-Repetitive Peak Surge Current rating > Fast trip threshold
    • Clamping voltage at fast trip threshold less than -0.3V
  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi Given Ding,

    The current during short circuit can be very high. In case of short circuit the Hotswap controller detects the over current and turns OFF the FET very quick, typically in few us.

    So, you can consider the  short circuit current = current corresponding to Fast trip threshold.

    The fast-trip threshold for this device is 60 mV. The fast trip current would be = 60 mV/Rs

    We would recommend to follow at least the below 2 conditions,

    • A DC blocking  voltage rating much higher than the Vinmax
    • Non-Repetitive Peak Surge Current rating > 1.5 x Fast trip threshold of the controller