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BQ76952: Temperature measurement result is not accuracy when operating in high temperature

Statham Su
Genius 4990 points
Part Number: BQ76952

Hello Sir:

We are using BQ76952 and testing the protections.

We found that temperature measurement is not accuracy when operating in high temperature.

Please refer out tested results as below.

According our tested results that measurement results has 4.58 degree tolerance when 52.4 degree, 10.1 degree tolerance when 66.9 degree.

I provide our GG.csv file, NTC.pdf datasheet and our "bq769x2 Family Thermistor Coef Calculator.xlsx" for you reference.

Please help us to check and let us know how to fix this issue.

Thanks a lot.

SC103F3950FB45BISX.pdf

8625.bq769x2 Family Thermistor Coef Calculator.xlsx

  • 0
    TI__Guru* 81034 points

    Hi Statham,

    I used our internal tool to calculate better temperature coefficients. Can you try these coefficients and let me know if you see an improvement in performance?

    A1 = -10923

    A2 = 5461

    A3 = 5461

    A4 = 27306

    A5 = 5461

    B1 = -32723

    B2 = 24429

    B3 = -8161

    B4 = 4291

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Genius 4990 points

    Hi Matt:

    Thanks your help, the tested results becomes normal.

    I think there has two difference curves.

    Can you provide an explain about correspondence between old parameters and new parameters?

    Also can you provide your calculator tools for me?

    Thanks a lot.

  • 0 in reply to Statham Su
    TI__Guru* 81034 points

    Hi Statham,

    The spreadsheet tool was developed first and works well for many thermistors, but some customers reported accuracy issues with some thermistors. So my colleague started working on a new tool in Matlab which is what I used. Unfortunately we cannot share it in its present form because it contains proprietary information about the device. We plan to make this tool available in the future, but we need to make it an executable and we need to make it faster (right now it takes 1-2 hours to calculate the coefficients).

    For now, we can help to calculate coefficients until the new tool is released publicly. 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Genius 4990 points

    Hi Matt:

    Understood your action, but our customer use Bq76952 temperature to calculate their battery pack SOC/FCC/RM and other pack parameters,

    They wants to know correspondence between old parameters and new parameters.

    Such as the ratio between old parameters and new parameters.

    Do you have this guide?

    Please provide recommendations for us.

    Thanks a lot.

     

  • +1 in reply to Statham Su
    TI__Guru* 81034 points

    Hi Statham, 

    There is no simple way to compare the parameters. These parameters are polynomial parameters to fit to the resistance curve of the thermistor, so there is no easy direct relationship. The old tool tries to calculate the parameters, but the new tool does a sweep of all possible values to find which parameters will give the most accurate result to match the polynomial to the resistance curve.

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Genius 4990 points

    Hi Matt:

    Thanks your quick response and recommendations.

    We are looking forward to your new release calculator in the future.

    Thanks again.