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TPS40400: Fusion Digital Power Designer I2C Issue

Part Number: TPS40400


I have a customer who has designed the TPS40400 onto their board, and they are having an issue connecting to Fusion Power Designer. They are using the TI USB Interface Adapter (connecting only SDA and SCL, not the Alert line), and they are getting the message shown below:

They verified they are seeing the correct input and output voltage for the regulator. Do you have any ideas why they can't connect to the GUI via i2c? I can share their schematic if need be. 




    The first item that I see is that the interface dongle is configured for Open Drain, so the interface is relying on pull-ups on the board, so double check to make sure the board they are interfacing with has on-board pull-ups for the I2C interfaces and the CLK and DAT lines are 3.3V or 5V when there is no communication. 

    If the board does not have on-board pull-ups, you'll want to click the drop-down menu buttons to the left of "Open Drain" for the CLOCK and DATA pullup and select one of the integrated pull-ups such as the 2.2kOhms pull-up.

    If the board has integrated pull-ups, and an oscilloscope shows valid I2C traffic on CLOCK and DATA, check the Device Scanning Options and make sure the expected address for the TPS40400 is being scanned and is not disabled.

    If both of those check out, let's take a look at the schematic.

  • Hi Peter,

    My customer changed the pull ups on the board from 10kohms to 2.2kohms. I2C communication picked up after that. Thanks for your help.


  • Thank you Daniel.

    Most likely, the 10k pull-ups to a 3.3V rail were not providing a fast enough rise-time to effectively create "logic 1" values for 400kHz communications.  I am glad we were able to address the issue.