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BQ76952: Why BQ76952 can support random connection

Miles Li1
Intellectual 1640 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQ76940

Hi,

Compared to BQ769X0, BQ76952 support random connection. I know that withstand voltage of sense pin is higher, but could you described in detail, why BQ76952 could support random connection, better with diagram. 

Thanks!

  • 0
    TI__Guru 54715 points

    Hi Miles,

    The structure of the BQ76952 is different from the BQ76940.  The inputs on the BQ76952 are referenced to each other and the VSS reference, see figure 16-1 and 16-2 of the data sheet compared to the BQ76940 which has inputs referenced to the intermediate power pins, see figure 15 of its data sheet.

    As you note, the absolute maximum of each cell which can be 85V on the BQ76952 is a significant advance from the 9V of the BQ769x0, and other than VC0, each input can go to 85V vs the stepped limit of 7.2V/cell of the BQ769x0. 

    I can't think of  a diagram which would illustrate this at this time, but that is a great suggestion.

  • 0 in reply to WM5295
    TI__Intellectual 1640 points

    Hi,

    Thanks for your reply. I don't think high withstand voltage at Vsense pin could solve the problem of random connection, because when VC0 is not connected to GND, even if we out 100V input voltage to input pin, they wiil not be broken down because they are not the same GND.

    How do you comment about that?

    Thanks!

  • 0 in reply to Miles Li1
    TI__Guru 54715 points

    Hi Miles,

    See section 16.3 "Random Cell Connection Support" of the data sheet for a description, particularly the note.  VC0 is expected to be connected to GND on the PCB, it is not intended for remote sensing of the cell on this device.  Also note the clarification that random cell connection is not abnormal voltages but the proper voltage for that cell.

    The BQ76952 is not a 100V part, the highest absolute maximum ratings are 85V, see the data sheet section 7.1 "Absolute Maximum Ratings"