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LMZ10500: protection diode required?

Muffin
Intellectual 2055 points
Part Number: LMZ10500

Hi,


Is a protection diode required on LMZ10500 between Vin and Vut or does it have internal protection circuit?

Thanks!

  • 0
    TI__Expert 3611 points

    Hi,

    The LMZ10500 has integrated Output Short Circuit Protection and Thermal Overload Protection as described on pages 10 and 11 of the LMZ10500 datasheet.
    If you are thinking about reverse current protection then adding a diode between Vin and Vout will not work since the internal High-side MOSFET has a body-diode which will bypass the external diode you want to connect. For reverse current protection I recommend checking out some of our load switches.

    Regards,
    Davor

  • 0 in reply to Davor Pavlovski
    TI__Intellectual 2055 points

    Hi Davor,

    Thanks for your reply.

    If I understand you correctly, if this condition occurs (Vout>Vin), the internal high side MOSFET diode will discharge the output capacitors without internal damage to LMZ10500. Therefore, an external diode is not needed?

  • 0 in reply to Muffin
    TI__Expert 3611 points

    Hi,

    If the voltage at VIN goes lower than the set VOUT and EN is high, then the device will enter 100% mode, where the high-side MOSFET is constantly ON, like described in section 7.4.8 of the LMZ10500 datasheet. In that condition VOUT=VIN - I*Rdson and the current protection circuit will be active.

    In the case the device is disabled and somehow there is a fixed VOUT voltage that is higher than VIN, then the body-diode of the high-side MOSFET will conduct and in that case there will be no current-protection implemented. Please see the following app-note for more details about your question: Testing tips for applying external power to supply outputs without an input voltage. If the device is enabled however and you have a fixed VOUT that is higher than VIN then the device might operate in a "boost-mode", which is not recommended as described in point 6 of the app-note I linked (also the fixes for these issues are written in the app-note). 

    Regards,
    Davor