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TPS25750: I2C port behavious when part is unpowered

Oscar Mitchell66
Prodigy 170 points
Part Number: TPS25750

I want to use the I2C port of the TP25750D in a self powered device.

It would be convenient to share the I2C slave port of the TPS25750D with other peripherals.

The TPS25750D might be completely unpowered while other peripherals are powered.

What will this do to the I2C bus?

The absolute maximum ratings in 7.1.1 of the data sheet indicate that the port is tolerant of -0.3 to 4V. I would have expected something more like -0.3 to LDO_3V3 - 1V or something

Fig 9-24 of the data sheet indicates the structure connected to the pin but has no indication of ESD structures (which must be there).

It may be that I need some form of I2C isolation to allow the rest o fthe I2C bus to function during complete power down of the TPS25750D.

  • 0
    TI__Genius 15275 points

    Hi Oscar, 

    If PD is unpowered and the I2C lines are connected, this should have no effect on operation on I2C bus lines since these lines are externally pulled up and PD I2C lines are open drain.

    Abs max rating is 4V as this is around 20% tolerance of operating voltage as the I2C lines operate off of 3.3V logic. 

    No isolation is needed as these pins are open drain, only instance where isolation would be needed if there is not a shared common ground in the system.

    Regards,

    Brandon