• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 46 subscribers
  • Views 224 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADC121C021: I2C problem at 400 kHz

Scott Brenneman
Genius 3295 points
Part Number: ADC121C021

We're bringing up a new design using the ADC121C021, and we're having difficulty communicating with it over I2C at 400 kHz, but 100 kHz is okay.  The first thing I thought of was to check the bus waveforms, but they look okay, with the rise time at 220 ns, well under the 300 ns max.  We don't get bus errors, but when reading registers we get erroneous data.  Is this IC unusually sensitive, or does it need to somehow be told that the bus is at 400 kHz?  I don't see anything in the datasheet indicating that.

Thanks,

Scott

  • 0
    TI__Mastermind 25020 points

    Hello Scott, 

    This device is not unusually sensitive, and standard and fast mode operate the same in this device. 

    Would you share the scope shot demonstrating an erroneous register read? this will help to make sure all timing requirements are being met. 

    Would you describe in more detail about the erroneous register read?

    Regards

    Cynthia

  • 0 in reply to Cynthia
    Genius 3295 points

    We figured out the problem, which I report somewhat sheepishly: we were powering the IC from a 2.048 V reference, which is below the 2.7 V minimum.  Sorry to waste everyone's time!

    Scott