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Need a reference design for 4S1P fuel gauge and cell balancing circuit that I can get parts for.

Kipton Moravec
Expert 1515 points
Other Parts Discussed in Thread: BQ20Z70, BQ20Z90, BQ40Z50, BQ40Z80, BQ34Z100-G1

I am trying to find a reference design for a 4 cell lithium battery (18650, 26650, 21700) pack 4S1P.

I found slua404 "bq20z70 and bq20z90 Application Book" which goes into detail about the BQ20Z70EVM for the evaluation. And had a reference circuit with bq20Z90DBT and BQ29330DBT on it.

I looked for the BQ20Z70EVM-001 referenced and it is obsolete. And I looked for the BQ20Z90DBT and Mouser says 52 week lead time, not stocked. I looked for the BQ29330DBT and did find stock.

The part searches on the TI website have been pretty frustrating because I can not search for chips that support 4S1P (or I do not know how to search for it.)

I am designing a battery pack that will need to be recharged often but we can limit the charge/discharge to stay between 80% and 25% for maximum cycles. 

I would like to know what combination of fuel gauge and cell balancing chips I should use. This is low quantity so price is not an issue. Availability is an issue. I have to be able to get them.

What parts are recommended? I am starting from scratch so I am open to anything that will work, that I can get. And a reference design to get me started. 

Thanks,
Kip

  • +1
    TI__Guru** 103125 points

    Hello Kip,

    I would not recommend the BQ20zxx family for new designs, these are mostly left in production for legacy support in older projects.

    You can use the search here: https://www.ti.com/power-management/battery-management/fuel-gauges/products.html

    Select the cell count and any other specifications for the gauge. The top results are the newest releases and should be considered first.

    For 4S gauges, the BQ40Z50 is the most highly recommended, the BQ40Z50 has cell balancing and CHG/DSG FETs for additional protection.

    The BQ40Z80 supports up to 6S and has many of the same features as the BQ40Z50.

    If you only need a gauge or you don't have access to the cell tabs, the BQ34Z100-G1 can be used as a top of stack gauge, but it doesn't provide any protections or cell balancing.

    You can find the EVM design files for the BQ40Z50 here: https://www.ti.com/tool/TIDA-00883

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Expert 1515 points

    I do not know how to find that search link on my own, but thanks for the link.

    It ended up with 4 choices and only one had stock. So the BQ40Z50 it is.

    That saved me a lot of time.

  • 0 in reply to Wyatt Keller
    Expert 1515 points

    The search said there was stock, but when I went to look, there were no samples available and Digikey and Mouser do not have any.

    How do I make a prototype?

  • 0 in reply to Kipton Moravec
    TI__Guru** 103125 points

    Hello Kip,

    We don't directly deal with the stock of parts on the forum, it is mostly for technical questions.

    Digikey and Mouser would be the best place to start looking, you can also start testing using the EVMs to start prototyping faster if they're in stock.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Expert 1515 points

    The whole point of the message was to find something that I could build a few prototypes of now. The search said there was stock, so I thought I was good. But when I looked, there was no stock at TI, No samples from TI, No stock at Mouser and No stock at Digikey.

    For now I only need 4 for two prototypes. I am hoping that will out last the chip shortage, assuming it lasts another 6 months.

  • 0 in reply to Kipton Moravec
    TI__Guru** 103125 points

    Hello Kip,

    You would need to contact the distributor, or your assigned FAE who can connect you with the proper contacts at TI for supplying samples.

    As I mentioned we don't directly deal with supply on the forum, the purpose of the forum is technical questions.

    Sincerely,

    Wyatt Keller