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BQ40Z80: SMBus communication problem

Jerry Schipper
Prodigy 10 points
Part Number: BQ40Z80

Hello,

I am currently working on a project where we use the BQ40Z80 connected to 18650 cells. We have a problem with the communication between the BQ40Z80 and the mcu where our mcu is not I2C compliant in its support for clock stretching. This results in the communication to get out of sync when the first clock pulse after the clock stretching to be shorter than ~1.5-2 us, as shown in the images. The first images shown the error occuring during a word read operation and the second images shows it occuring during a block read operation. The data sheet of the BQ40Z80 specifies that clock stretching can be disabled using the FLASH_BUSY_WAIT bit (bit 7) in the setting SBS configuration. However, when I use the Battery Management Studio to find this bit, it says that it is reserved. Disabling this bit has no effect on the clock stretching.

Is there a way to fully disable clock streching on the BQ40Z80? Or maybe a setting that causes the BQ40Z80 to recognize clock pulses as short as 0.6us?

Kind regards,

Jerry

  • 0
    TI__Guru** 105760 points

    Hello Jerry,

    This bit only operates during flash writes, if you are using SBS commands it will not prevent clock stretching.

    I'm checking if we have a bit that can control the clock stretching with SBS commands, but it may not be possible as this is used to sync the two devices if the primary device SCL line isn't matched.

    Sincerely,

    Wyatt Keller