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BQ76952: 32S stacked BQ76952 support thread.

Abhijith V Narayan
Intellectual 446 points
Part Number: BQ76952
Other Parts Discussed in Thread: TIDA-010247, BQ76942, LM5168

Tool/software:

Hello experts,

We are initiating a design for a BMS for cells upto 32S using BQ76952. We are basing the schematic off of TIDA-010247 by Mr. Ryan Tan. I am hoping this thread can serve as a support thread for the development of this design.

Although TIDA-010247 is based on BQ76942, our design will be using BQ76952 and the Li-ion cell we are using will be having a max voltage of 4.2V and hence the total system BAT voltage will be ~135V. In general I am trying to understand what components or section I will need to redesign because of the higher system voltage.

So, here are the questions we have currently:

  1. We cannot be using the power section from the reference design. Do you have an alternate part from TI's portfolio for the same?
  2. Can you tell the function of D1 and D4. Should I be sizing it for the higher voltage?

Many thanks,

Abhijith

  • 0
    TI__Genius 17725 points

    Hello Abhijith,

    Abhijith V Narayan said:
    We cannot be using the power section from the reference design. Do you have an alternate part from TI's portfolio for the same?

    As for alternate parts from TI’s portfolio outside of the BQ76952, one method you could try is using TI’s product page for each individual highlighted green product and try to filter out for the parameters your system would need for that part. For example, the LM5168 is a synchronous buck converter that falls under the ‘AC/DC & DC/DC Converters (integrated FET)’ page (https://www.ti.com/power-management/acdc-dcdc-converters/products.html). From that page, you can filter the results to suit your desired parameters.

    As other parts outside of the BQ76952 do not fall under our team, you may want to reach out to those teams regarding any better recommendations.

    Abhijith V Narayan said:
    Can you tell the function of D1 and D4. Should I be sizing it for the higher voltage?

    D1 and D4 to my knowledge, should not be needed. I will, however, double check with my team and review it further.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Intellectual 446 points

    Hello Alexis,

    1. Okay, will check.

    2. Okay, awaiting your confirmation.

    Further question:

    3. Can you tell me how this circuit affects cell balancing of the bottom stack? (From sheet 6 of TIDA-010247)

    Thanks,

    Abhijith.

  • +1 in reply to Abhijith V Narayan
    TI__Genius 17725 points

    Hello Abhijith,

    Thank you for your patience. 

    2. After checking with the team further, it looks like they are designed to bypass the current if Cell 10/Cell 20 has an open wire. Cell 10 is also being used as the LDO REGIN power source as well in this reference design.

    3. I think that this circuit allows the bottom stack of the cells to balance and match the top stack of the cells as each device cell balances individually from each other. I will double-check with the team to make sure. Please refer to the Design Considerations of Stacked BQ769x2 with High-Side N-MOSFETs and Cell Balancing with BQ769x2 Battery Monitors application notes as well for reference.  

    Best Regards,
    Alexis