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BQ76930: Hardware Implementation to meet IEC Safety Compliance

Jerry%20Leung
Intellectual 905 points
Part Number: BQ76930
Other Parts Discussed in Thread: BQ7718

Hi Team,

I have a question from a customer and I want to run it by here and see if we have any good suggestions or similar implementations in the past:

Our customer is going through IEC compliance testing right now, per safety test requirements from a 3rd party (TUV). According to IEC 62169 “8.2.2. Overcharge control of voltage (battery system)”, our BMS must have a way to prevent over charging. This is obviously what the IC is designed for, however it is firmware programmable, and as such there are additional (i.e. costly for both time and $) testing requirements.

Their preference is to meet hardware safety requirements, yet not require additional firmware test for the BMS. Is there a fusing methodology / tool or custom order sku system for this part #, which masks out specific values such that they would not ever misconfigure it to exceed our battery ratings? For example, our cells have a max voltage of 3.65V. If we fuse the BQ76930 such that setting anything above it will not be valid (below is okay), it might be sufficient from a safety perspective. Or if you have alternate approaches that other BQ769xx customers have done with regards to IEC safety certification testing, that would be really helpful. They could also design a separate sense circuit for compliance, but perhaps this is most elegant and most cost effective; any reference circuits here would be useful as well if this is the path.

Thanks for the help and insights here.

Best regards,

Jerry

  • 0
    TI__Expert 5090 points
    Hi Jerry,

    I am not familiar with the specifics of IEC 62129, but our customers typically address safety requirements by including a secondary protector IC together with the bq76930 (which functions as the primary protector). The focus of many standards is to be safe in the presence of a single failure that may occur, so if the bq76930 failed to function properly, the secondary protector can still provide protection for the system and disable charging when an overvoltage condition occurs.

    The secondary protector (such as bq7718) is shipped from TI with its settings already configured, it cannot be programmed by the user in system, so this removes the risk of the customer uC incorrectly setting a threshold.

    Thanks,

    Terry