• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 698 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.

BQ20Z45DBT-R1 NAKS

Casey Shea
Prodigy 185 points

i am currently using a BQ20Z45DBT in my design and,  periodically, the device NAKs SMBus commands.  I currently have it built in to allow up to 5 successive NAKs before reporting an error.  If I reduce that number to 2 or 3, I see many more reported errors.  I don''t believe there is anything in the user guide or datasheet that references run-time operation periods in which the unit is unable to communicate and will NAK but it seems like this is what is happening.  Could it be that the battery management IC is performing time critical operations and is just unable to execute lower priority tasks (such as SMBus communication)?  I can dig in deeper and verify that there are no timing errors on the bus but I wanted to check first to see if this is expected behavior.

  • 0
    TI__Guru 73830 points
    Casey,
    The gauge does have higher priority interrupts than servicing SMBus requested and it will stretch the clock low pulse until it can respond. I have not noticed it NACKing commands. Do you see cases where it stretches the clock pulse? Maybe something in the system is preventing this.
    Tom
  • 0 in reply to ThomasCosby
    Prodigy 185 points
    Thanks, Tom. The issue certainly was related to clock stretching by the gas gauge. I was only supporting clock stretching during the ACK transfer. After looking at the SMBus specification, I noticed that I need to be supporting clock stretching by the slave devices at every bit transfer. Thank you for your help!