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SMBus and PMBus interoperability

Jamie Maxwell
Expert 1530 points
Other Parts Discussed in Thread: TMP101, UCD9090, TMP103, TMP103EVM

I am wondering about the interoperability of putting an SMBus/I2C part on a PMBus.

With some limited investigation I am able to determine that PMBus is based on I2C/SMBus which leads me to believe that these are in fact compatible.

More specifically we are controlling UCD9090 via PMBus and would like to add a couple of TMP101 to the same bus. Has anyone here done this?

Thanks

J

  • 0
    Prodigy 5 points

    I tend to agree with your assessment.
    As long as you keep the addresses different on all the devices it should work.

    At the lowest level, PMBus follows SMBus 1.1 with a few differences.
    PMBus allows 400 kHz bus speeds vs. the 100 kHz limit of SMBus.
    This would be the major one.

    Keep the clock speed within SMBus limits and address each device uniquely. 

  • 0
    TI__Guru 71526 points

    As an example, the TMP103EVM has eight TMP103s attached to a common SMBus; each TMP103 has a unique address:

     

    • TMP103EVM Schematic
    		 PDF 24 21 Jan 2011 216
    • SM-USB-DIG Platform Schematic
    		 PDF 37 13 Jan 2011 155
  • 0 in reply to LeonardEllis
    TI__Intellectual 1695 points

    Hi Team,

    Follow up question from the customer:

    We need to generate an interrupt when the power goes off so that we can shut things down in an orderly fashion.  I'm wondering if we could use the one last spare input to the UCD9090 to warn of pending power failure?

    Thanks guys for helping out with this.

    Best Regards,

    Shashank

  • 0 in reply to Shashank Reddi
    Prodigy 5 points

    The GPIO's can be configured as an output for an event.

    UV under voltage can be measured on VMON and create a GPIO transition when the UV occurs.
    Just like a GPIO can be configured to go high when a rail gets within spec, it can go low when a rail goes out of spec.