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UCC28180: Want to determine whether we need to use the diode

Phil Barnett
Prodigy 20 points
Part Number: UCC28180

We are using your IC UC28180D and  found some discrepancies in a datasheet regarding the absolute maximum voltage on Isense Pin 3. Table says it can not exceed -24 to 7
But Application says -1.1V and the diode should be used to clamp voltage below -1.1V.

Is it still required to use clamping diode on that Pin if voltage is much above than -24V.


This is quite urgent for us

Thanks for your support.

  • 0
    TI__Mastermind 25570 points
    Hello Phil

    I'll agree that it's a bit confusing but the answer is yes - you will need to use the diode. The -24V refers to device breakdown and damage in a static situation - however in a dynamic situation - where the controller is active - if the ISENSE voltage goes too negative you can get an incorrect switching pattern which may over current the switching device and destroy it.

    The diode protects the ISENSE pin from excessive voltages such as are caused by inrush currents as the PSU is starting up. If you have an inrush limiting circuit such that the voltage developed across the current sensing resistor is less than 1.1V under ALL circumstances then you may not need the diode.

    Please let me know if you need any more information

    Regards
    Colin