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BQ76940: Connecting batteries with connectors

Yoshinobu Kagawa
Expert 2030 points
Part Number: BQ76940

1) Battery Connection Order for the BQ76940
    Section 10 of the BQ769x0 Family Top 10 Design Considerations document states that multiple series batteries should be connected from the low voltage side.
    When connecting batteries with connectors, the connection order cannot be controlled.
    How should I connect the connectors?

2) BQ76940 Handling of NC (pins 11 and 12)
    I am instructed to connect to CAP2 even though it is No Connection. Is this connection necessary?



regards,
Kagawa

  • 0
    TI__Mastermind 42060 points

    Hello Kagawa-san,

    1) Battery Connection Order for the BQ76940. Section 10 of the BQ769x0 Family Top 10 Design Considerations document states that multiple series batteries should be connected from the low voltage side. When connecting batteries with connectors, the connection order cannot be controlled. How should I connect the connectors?
    BAT-/VSS should always be connected first to ensure there is no damage. As long as this is ensured, things should be fine. More so if following the recommendations detailed in Section 10 of the app note. If you can somehow get connectors that ensure Vss touches first, that would be ideal.

    2) BQ76940 Handling of NC (pins 11 and 12). I am instructed to connect to CAP2 even though it is No Connection. Is this connection necessary?
    Yes. You should short these to CAP2 as recommended by the datasheet.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Expert 2030 points

    Hello Luis-san,

    1) At the customer, after the BAT-/VSS is first connected, there is damage even if the cells are connected randomly.
        Is there any other way to connect the cells with connectors (when cells are connected randomly)?
        BTW, NC pins (Pin 11 and 12) are not connected to CAP2. (Open)
        Are pins 11 and 12 affected?

    2) When TEMP_SEL = 1, if the thermistor is disconnected, the voltage value cannot be read.
        In case of this, NC pins (Pin 11 and 12) are not connected to CAP2. (Open)
        Are pins 11 and 12 affected?

    Regards,
    Kagawa

  • 0 in reply to Yoshinobu Kagawa
    TI__Mastermind 42060 points

    Hello Kagawa-san,

    There are lots of discussions in Section 10 Random Cell Connection – Within Limits of the Top 10 Design Considerations app note about some of the things that can be done to prevent damage to the parts. Like the addition of diodes on certain pins.

    PIN11 and PIN12 need to be connected to CAP2, I am not exactly sure how they connect internally, but there is a risk of the device not working properly if not following these recommendations. Please connect these before further testing.

    Best Regards,

    Luis Hernandez Salomon