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MCF8316A: I2C NACK, DVDD is at 0V

Evan Zhao
Prodigy 20 points
Part Number: MCF8316A

Tool/software:

Hi,

I was trying to program the MCF8316A chip using I2C and realized that I kept getting NACKs. I read some forum posts and learned that it relied on DVDD and the buck output. Measuring these, we found that they were both at 0V while AVDD is properly at 3.3V. Can you see any problems with the schematic and layout I currently have?

Thank you!

  • 0
    TI__Expert 6011 points

    Hi Evan,

    Thanks for reaching out. DVDD powers the digital circuit of the device and without DVDD I2C will not be functional. Could you capture the waveform of the voltage on FB_BK? And what is the status of the Speed pin?

    Regards,

    Sachin S

  • 0 in reply to Sachin S
    Prodigy 20 points

    Hi,

    The voltage at FB_BK is 0V as shown in the image below.

    The Speed pin is connected to an ESP32 and at 0V.

    AVDD is at 3.3 V. 

    Using a multimeter and testing continuity with no power connected to the board, it seems to be detecting that SW_BK, Speed and DRVOFF pins are shorted to ground. These may be soldering errors that we will try to fix. However, since we are already pulling Speed and DRVOFF to ground externally with the ESP32, I don't believe these two should be affecting the buck output. I'm not sure about SW_BK. 

    Does the Schematic and PCB layout in my initial post look to be correct?

    Thank you!

  • 0 in reply to Evan Zhao
    TI__Intellectual 1850 points

    Hi Evan,

    Please make sure that the components around MCF8316 including decoupling capacitor values are selected as recommended by datasheet. You can also consider using the MCF8316C

    Regards,

    Manu

  • 0 in reply to Manu Balakrishnan
    TI__Expert 6011 points

    Evan,

    Could you externally force FB_BK to 3.3V and let me know if the device is functional.

    Regards,
    Sachin S

  • 0 in reply to Sachin S
    Prodigy 20 points

    Hi Sachin,

    Thank you for the help so far. We found that it was a soldering issue and ended up reordering the PCB and had it assembled by them as well. DVDD is now at 1.53 V and FB_BK is around 5V. I'll let you know if we have more issues getting it to work with our motor.

  • 0 in reply to Evan Zhao
    TI__Expert 6011 points

    Hi Evan,

    Great to hear that! I will close this thread for now. You could create a new question and we would be happy to help.

    Regards,

    Sachin S