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BQ77905: How can this part be safely used with 24-S cells?

Lauren Mayfield
Expert 7925 points
Part Number: BQ77905
Other Parts Discussed in Thread: BQ77915

Regarding the BQ77905 and BQ77915

bq77905 datasheet:
“The device's stackable interface provides simple scaling to support battery cell applications from 3 series to 20 series or more.”

“bq77905 supports 3-series-to–5-series cell configuration. Up to four devices can be stacked to support ≥6-series cell configurations, providing protections up to 20-series cell configurations.”

Bq77915 datasheet:

“The BQ77915 device supports 3-series to 5-series cell configurations. Up to four devices can be stacked to support ≥6-series cell configurations, providing protections up to a 20-series cell configuration. It is possible to support greater than 20-series cell configurations, but with careful consideration of delays.”

Do you have any information on how I can safely use these devices with 24 cells? I won’t actually be using the current sense or load detecting features and will likely use the DSG and CHG pins as fault indicators for OV/UV.

Thanks,

Lauren

  • 0
    TI__Expert 7465 points

    Hi Lauren,

    We do not have any technical limitation on how many devices you can stack. You will have to take into account that if a fault occurs on the top device, it will have some delay when sending that signal to the bottom device. I believe it is in the order of ms, so usually it is not an issue. 24S will also have a very high voltage, so general safety precautions should be taken.