• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 814 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.

BQ76940: Reading battery voltage value from chip

Mathias Bonn
Prodigy 50 points
Part Number: BQ76940

Dear TI team and forum members,

how do I calculate the voltage value from the "Battery Voltage" ADC raw value of the bq769x0 chip. I was able to calculate the cell voltages successfully, but I can't get any further with the battery voltage. I am aware that the delivered value is a sum of the cell voltages, but I would have to transfer fewer bytes if I could interpret the value correctly, which saves time and traffic on the bus.

Unfortunately, the only section in the documentation on this subject is incomplete. Please see the attached screenshots.

RAW 0x8F50 -> 36688 in decimal so what are the unknown factors? Also the ADC Gain and ADC Offset doesn't seem to be the answer.

Thank you in advance!

MaBo

  • 0
    TI__Guru 54715 points
    Hi MaBo,
    There is a factor of 4 applied to the value since at high voltages it could roll over beyond the 16 bits. See the bq76940 data sheet section 7.3.1.1.6 The device will include any residual counts of unused cells in its calculation, those may add up to some small error if they are large enough to make it through the divide by 4.
    When calculating the voltage value multiplying by 4 and the gain, when adding the offset do not apply offset for the unused cells.