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TPS549B22: pmbus function of TPS549B22

Part Number: TPS549B22

Hi team,

My customer is evaluating our TPS549B22.

They can not detect TPS549B22 on the I2C bus. The measurement waveform is shown below.

The address is 0x10. (1.78k pull down)

And it can operate in standard mode.

Could you help to check why can we get the response of pmbus at fast mode? Thanks.

  • Hello,

    It looks like the waveform attached contains the correct address (0x10) followed by an NACK. The logic levels look within spec as well. Are there any differences in the test set up when evaluating standard mode and fast mode PMBus communications with this device?


    Alec Biesterfeld

  • Hi Alec,

    Thank for looking at this issue.

    Customer have an old design, it use TPS549D22 and it can be access by I2C, so customer rework the make the I2C interface of TPS549B22 on Raisin connecting to the old design and make these 2 boards’ GND connected, but the TPS549B22 still can’t be detected.

    Is there any driver or any configuration need to set for it? 

  • There is not any specific driver nor configuration for it. The key detail is that VDD on the second device (Raisin) must be powered up. During power up the device will read the ADDR pin and set the PMBus address. There is a USB-to-GPIO adapter that comes with software the customer may use if they wish to communicate with the part on the EVM, but there process appears correct so long as VDD on the Raisin device is powered while they attempt to communicate. Is there another device on the Raisin board with a conflicting address?