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LSF0102: What happens if/when EN input is being driven below GND?

Alberto Aloisio
Intellectual 910 points
Part Number: LSF0102

Tool/software:

Dear E2E Staff,

in my application, the EN pin of the LSF0102 is driven by a long transmission line and, due to reflections, it could be driven below GND. I have noticed the voltage seems to be clamped at -0.5V. Is the EN (and hence the three gates) protected by a clamp diode? If so, what about the max negative voltage could be tolerated ? For how long? Thank you so much for your time and support.

Alberto

  • 0
    Guru 284830 points

    There is a diode. As shown in the absolute maximum ratings, if the voltage is below −0.5 V, the current must be limited to less than 50 mA (and the characteristics of the diode are not specified).

    The recommended operating conditions say that for voltages below 0 V, correct operation is not guaranteed. But the EN pin is simply connected to the gates of the three pass transistors, so there should not be any bad effects.

    Wouldn't it be possible to add source termination to the line? A 33 Ω or even 1 kΩ resistor would be insignificant compared to the 200 kΩ resistor in the bias circuit.

  • 0 in reply to Clemens Ladisch
    Intellectual 910 points

    Dear Clemens,

    thank you so much for yout prompt reply. I will follow your suggestion about termination.

    Kind Regards and Best Wishes for the New Year!

    Alberto