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Original question:

DAC43608: I2C time out function for abnormal communication.

DAC43608: Issue with I2C, only works when clock speed is slow <70kHz

TeeHowe Peh1
Prodigy 40 points
Part Number: DAC43608

Hi there,

I'm having issue with this part. When talking to the DAC with low speed (<70kHz), it seems to be working OK, but having some problems at normal (100kHz) and fast speed (400kHz).

Schematic and layout looks OK to me, but I wonder if I'm missing anything here, maybe a bad config, etc. Component and board looks okay on the microscope.

  • 0
    TI__Mastermind 25433 points

    Hello,

    Can you scare an oscilloscope shot of the I2C lines at the low speed where you have successful communication, and at a higher speed? Also, what is the value of the I2C pullup resistors? I do not se them in your schematic. 

    Thank you,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Prodigy 40 points

    Hi Katlynne,

    This is how it looks like at 100kHz. The plot at 20kHz looks similar, .

    Our firmware engineer managed to find out there's a short delay sequence that wasn't immediately obvious that actually allows the DAC to operate correctly now. I wonder if this information was in datasheet, or perhaps I might have missed this information. Thanks!

    Pull up to 3V3

  • 0 in reply to TeeHowe Peh1
    TI__Mastermind 25433 points

    Hello,

    Hello,

    I'm glad you and your team were able to solve the issue. There are a few required delays according to the timing requirements table:

    I wonder if you are referring to tbuf, which is the time SDA needs to be free between start and stop conditions.

    Best,

    Katlynne Jones