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TPS65381A-Q1: VDD5 VDD3/5 and VDD6 current sinking ability

Theo Kachelski
Prodigy 30 points
Part Number: TPS65381A-Q1

In our design we have diode clamps up to 5 volt and 3.3V rails that are supplied from the TPS65381. For example, on a sensor input we don't want the voltage to go much higher than 3.3V so we have a diode up to 3.3V rail to clamp the sensor input to a max of ~4V.  I would like to know how the TPS65381 will handle this extra current.  If there is a high amount of current being sunk into the rail will the TPS sink the extra to ground, back to VBATP, or will it not handle the extra current and the voltage on the rail will increase leading to an overvoltage condition?  

I could not find the answer in the datasheet, any help is appreciated,

Thanks

  • 0
    TI__Genius 12735 points

    Hi Theo,

    What voltage levels are you designing these diodes to clamp at? This device has internal voltage monitoring to ensure that the regulation is within the specified monitoring windows. As long as the sensors able to withstand voltages within the voltage monitoring windows then there should not be a need to incorporate such clamping diodes into the system.

    Best regards,

    Layne J

  • 0 in reply to Layne J
    Prodigy 30 points

    The diodes are clamping other input circuit to the rails supplied by the TPS65381. Like this

    In this simple example D1 will sink any voltage above ~4V to the 3.3V rail.  I want to know how much current the 3.3V rail can take and what happens to the excess current.  Does it go to VBATP, GND, or will it raise the rail causing an overvoltage condition.  In other words, if I put 36V on the input what will happen to the 3.3V rail?

  • 0 in reply to Theo Kachelski
    TI__Mastermind 23655 points

    Hi Theo, 

    Due to the Thanksgiving holiday in the U.S. our TPS65381A-Q1 experts are out of office this week. Please expect a response early next week. Thank you for your patience. 

    Best Regards,

    Garrett 

  • +1 in reply to Theo Kachelski
    TI__Genius 12735 points

     Hi Theo,

    The TPS65381A-Q1 device is not designed to sink power at the regulator outputs and doing so with this device can cause damage to the regulator MOSFETs as well as other portions of the device. I cannot give any specific information about what will happen during these use cases as they are not supported.

    Best regards,

    Layne J