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Original question:

BQ76952: BQ76952

BQ76952: Lower series cell count

PRABHAT RANJAN TRIPATHI
Expert 1102 points
Part Number: BQ76952
Other Parts Discussed in Thread: , BQ34Z100-G1

Hey, I have few questions regarding BQ76952

1. I am trying to figure out if it is possible to use BQ76952 for a reconfigurable BMS (4S to 9S) in which the user can without any tweak with PCB (for ex desoldering)  just plug different series cell packs to the BMS? This is confusing to understand as It has been mentioned in section 10.1 of the datasheet that each series cell should be connected with the VCx pins with a series resistor and bypass capacitor; further it has been mentioned in section 10.2 that to reduce the cell count adjacent cells can be shorted . What is unclear is what happens to the resistor and bypass capacitor which are already populated on the PCB for the missing cell i.e. is desoldering required?

2. Is the source code for MSP used in TIDA001030 available?

3. Why does BQ76952EVM not include external balancing MOSFET and Resistor?

  • 0
    TI__Guru* 81034 points

    Hi Prabhat,

    1. You can short adjacent cell to reduce the cell count. The easiest method may be to replace the cell capacitors with 0-ohm resistors. The resistors and capacitors will not matter if you are providing a direct short for these pins. The only requirement is that the top cell pins (VC16-VC15) and the bottom 2 cells (VC1-VC0 and VC2-VC1) need to connect to cells. All other cell inputs can be shorted as needed.

    2. We do not have this code available to share. This TI Design does not use the BQ76952 though. If you are looking for sample code to talk to the BQ34Z100-G1, I have noticed many users have shared code on sites like Github, so I think you can find examples.

    3. The BQ76952 can support pretty high balancing current using internal balancing, so not all users will use external components. There are also multiple options for balancing externally (NFETs, PFETs, BJTs), so it is really dependent on the end application. The Cell Balancing app note shows the different circuit options and some test results. https://www.ti.com/lit/pdf/sluaa81 

    Best regards,

    Matt