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UCD9090-Q1: I2C Address Response

Justin Bohr
Mastermind 27880 points
Part Number: UCD9090-Q1

Tool/software:

Hi Team,

With 2x UCD9090-Q1 in the system, the PMBus_ADDRx resistors are as follows:

Device 0:

Expected Address: 0x34

PMBus_ADDR0: 31.6kOhm

PMBus_ADDR1: 31.6kOhm

Device 1:

Expected Address: 0x41

PMBus_ADDR0: 41.2kOhm

PMBus_ADDR1: 41.2kOhm

However, when they run an I2Cscan in Linux on this I2C bus, they only get responses from addresses 0x0C and 0x7F. Even with an 8bit vs 7bit adjustment that doesn't explain these two responses. Do we know if there is any reason the UCD9090-Q1 would respond to 0x0C or 0x7F?

Thanks,

Justin

  • 0
    TI__Expert 7140 points

    Hi, Justin,

    Address 0x0C is "PMBus Alert Response" => Device responses to address 0x0C if device pull ALERT line low. Address 0x7F (127d) is prohibited, not sure why it happens. Please check your voltage on ADDR0 and ADDR1 pin, make sure they are within the voltage range as defined in ucd9090 datasheet

    Regards

    Anne Ngo