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LMR16006: Can we have 5V connected to VOUT when VIN is floating?

Ales Stojan
Prodigy 170 points
Part Number: LMR16006

We have application where we can supply VOUT=5V from two power supplies (but only one can be present at a time, choosen by jumper). If we supply 5 V from other power supply, can output of LMR16006 remain connected to this 5V (VIN to LMR16005 is floating) or we need to disconnect it because leakage current into LMR16006 output can harm it?

  • 0
    TI__Mastermind 23845 points

    Hi Ales,

    Do you have schematic of your circuit? Is this a diode OR configuration? Seems like you have a jumper already to disconnect one supply to another. 

    I would say that you disconnect LMR16006 when you have the other supply because without the VIN on the input of the LMR16006, the other 5V from the other supply will backfeed through the inductor and high side FET into the VIN of the LMR16006. 

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Prodigy 170 points

    Hi,

    if 5V from the otehr supply is present, VIN of LMR16006 is floating (just connected via input capacitor to GND). I have some problems with my browser, if I succeed I will attach schematics. But, if input of LMR16006 is not connected to any potential, I assume current into LMR16006 can't damage it? Or is its internal structure such that current via high side switch (or low side switch if it get's open) can internally damage it?

  • 0 in reply to Ales Stojan
    TI__Mastermind 23845 points

    Hi,

    I think it depends on how you connect the SHDN pin. Is it connected to VIN? If yes, then the part will start and try to regulate the output. 

    If not, then i think the part is in shutdown mode so no switching happens and no current will flow.

    You might want to consider this part also 

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Prodigy 170 points

    Thank you. Situation is clear to me, we will add additional MOSFET to disconect output. I also like your proposal about OR-ing, in our case it is not necessary to use it - we will try to keep it simple...