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BQ40Z50: Spark gaps - replace with capacitors or remove entirely?

Joseph DeWitt
Prodigy 190 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ40Z60, PMP

Hi,

In reference to Figure 21: Application Schematic of the BQ40Z50 datasheet on pg. 28 there are two spark gaps on the wire tracks associated with SMBD and SMBC which go to ground. My goal is to use this BMS for an intrinsically safe product, therefore sparks are something I am trying to avoid. Is it possible to replace the spark gaps with TVS (transient voltage suppressors) to address the issue of electrostatic discharge?  

I also noticed that the BMS for the BQ40Z60 IC does not include spark gaps (reference pg 30 of the datasheet) and only incorporates the 5.6 V zener diodes which I believe are also present in the BQ40Z50 IC. Assuming the diodes also provide some ESD protection, will they be equally sufficient for the BQ40Z50 IC and therefore can the spark gaps in the BQ40Z50 IC be removed if TVS's cannot be used instead of the spark gaps?

Best regards,

Joe DeWitt PE, PMP

  • +1
    TI__Guru** 102455 points

    Hello Joe,

    The amount of different methods used to suppress and ESD events is up to the designer, we include multiple different methods for reference. If you are not expecting anything to be exposed to ESD (everything is internal to an enclosure that isn't opened) then there may not be a need for ESD protection. If any of the lines will be touched or are connection points, they should have some kind of ESD protection, like TVS diodes.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 190 points

    Hi Wyatt,


    Thanks so much for the feedback. I greatly appreciate it. I anticipate leaving the SMBD and SMBC connections internal to the enclosure so it seems like those connections will therefore not be an issue. The external Pack + and Sys Pres connections will of course be external connections and therefore I'll have to address the ESD concerns with those connections. I will leave the two 0.1 uF capacitors which I'm interpreting as being for ESD protection and will substitute the spark gaps with TVS diodes. I believe this strategy should work but if you have any additional guidance it would be greatly appreciated. 

    Best regards,

    Joe DeWitt PE, PMP

  • +1 in reply to Joseph DeWitt
    TI__Guru** 102455 points

    Hello Joe,

    I think what you have explained is a good solution for your system. Any external connections should have some kind of ESD mitigation devices.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 190 points

    Thanks Wyatt! Really appreciate the help and feedback.

    Best regards,

    Joe DeWitt