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BQ27621-G1: Design Capacity of Part

Adam Bierman
Intellectual 710 points
Part Number: BQ27621-G1
Other Parts Discussed in Thread: GPCCHEM, BQ27421-G1, BQ27Z561

The design capacity on the website for this part shows 32000mAhr.  The TRM only indicates 8000mAhr.  Which is correct? Are ANY of the design capacity values featured in your website correct?  This is now the third chip I've had to look at due to mismatching TRM and website data.  I'd like to know if I should just stop relying on your website completely.

  • 0
    TI__Mastermind 24870 points

    Hello Adam,

    Sorry for your frustration. I will bring this up to the web team. I appreciate you posting on e2e so we can get this resolved.

    The bq27621 is a voltage based gas gauge. The design capacity does not need to be set from an applications perspective.

    This gas gauge has a generic chemID. The proper process is to check if your battery is supported by the default chemIDs using GPCCHEM tool.

    Once you determine if the chemID is a best match, you can leave the design capacity out of it and use this as an RSOC indicator.

    Hope this helps.

    My best guess, the 8000 mAh is a legacy term which was ported over from our bq27421-G1 devices. I see that the bq27421 had it corrected, but there's a few other items such as default design capacity that still show 32767 mAh. There is nothing stopping you from programming the device to a value of 32767 mAh in firmware, but we limited this device because it had an integrated sense resistor. Technically the sense resistor can support continuous of 2000 mA, so with a C/2 charge rate, this part ideally supports 4 Ah.

    You do not have that issue with a voltage based gas gauge, so the number can go as high as 32767, but you may want to try by leaving the design capacity default and using this purely as an RSOC indicator.

    If you want a more flexible device, you will want to look at the bq27z561 family of devices.