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BQ76952: temperature issue

Cherry Zhou
Mastermind 22235 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50

Hi team,

Here's an issue from the customer may need your help:

When testing the temperature protection, the OTC and OTD status bits are set regardless of charge or discharge, causing the charge and discharge MOS to turn off. The customer would to know what's the reason for that.

Could you help check this case? Thanks.

Best Regards,

Cherry

  • 0
    TI__Mastermind 42060 points

    Hello Cherry,

    Are they using any thermistors in their design? What thresholds do they have set? 

    If they are using bqStudio, what temperatures are these thermistors measuring?

    It would be useful if they are able to upload their .gg setting too.

    Best Regards,
    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Mastermind 22235 points

    Hello Luis,

    Using 10K Ntc, the TS1 pin, OTC is 45°C, OTD is 60°C, and the temperature is slowly added up with the blower. Tested in both charge and discharge states.

    .GG setting is as below:

    https://e2echina.ti.com/cfs-file/__key/communityserver-discussions-components-files/127/BQ7695202.gg.csv

    Thanks and regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 42060 points

    Hello Cherry,

    OTC and OTD can be set regardless of the charge/discharge state. It does not need to be in charge/discharge to be set, once OTC/OTD are set, they disallow charging/discharging respectively.

    So the device will not be able to enter charge/discharge until the respective OTC/OTD pin is cleared. At 45C, charging would not be able to occur, at 60C discharge would not occur. 

    This is mentioned in the descriptions of Sections 13.6.12 — Protections:OTC and 13.6.13 Protections:OTD of the Technical Reference Manual.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    TI__Mastermind 22235 points

    Hello Luis,

    Thanks for your help again!

    Here's the understanding from the customer:

    It's same as the BQ40Z50 temperature protection, when charging and the temperature reaches the OTC threshold, the OTC bit is set and the charging tube is turned off. The OTD cannot be set at this point, regardless of the temperature increase.

    When discharging and the OTD position is set when the temperature reaches the OTD threshold, and the discharge tube is turned off. At this point,  OTC  cannot be set regardless of the temperature increase. This should be normal protection, not "OTC and OTD can be set regardless of the charge/discharge state."

    Could you help clarify? Thanks.

    Best Regards,

    Cherry

  • 0 in reply to Cherry Zhou
    TI__Mastermind 42060 points

    Hello Cherry,

    No problem! Glad to help.

    The normal operation is what I have described. I pointed to the sections to the Technical Reference Manual sections that say so, Sections 13.6.12 — Protections:OTC and 13.6.13 Protections:OTD.

    This is what it says for OTC: "Note that charging does not need to be occurring for this protection to trigger. It is intended to be the threshold at which charging should not be allowed, not an indicator of if charging happened at this temperature."

    Best Regards,

    Luis Hernandez Salomon