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BQ76940: BQ76940

Part Number: BQ76940

Dear All:

    I am using the BQ76940 to design the 14S BMS can you answer the  following questions?

 1. From sleep mode to normal mode, reading the parameters requires a delay of at least 800ms?

  2. Does it need to initialize for each wakeup from sleep or only need to initialize  for the first time?

 3,if the balance is not turned off, will the cell  run out ?

 4.  whether the BQ76940 needs to be protected by temperature during  balance?and if yes  how to do?

 

  • Hi Big Bill,

    1. Parameters can be read after tI2CSTARTUP, but updated voltage data for all cells may not be available for 800 ms.  Cell voltages are converted  sequentially.  The application note Embedded Scheduler in Cell Battery Monitor of the bq769x0 may be helpful.

    2. The registers need to be initialized after each wakeup.  The registers are volatile and will be reset on boot.  Additionally the host may want to confirm register values periodically.  The CRC version device are available if desired.

    3. Balancing is not turned off by low voltage of the cell.  Note that balance is controlled by the host.  It is possible to balance a cell below UV while the overall operating voltage remains above VSHUT.  The balancing is not specifically turned off by entry to sleep mode, but if power is turned off balancing should be off.  The registers are cleared on boot. 

    4. Note that the part has a thermal shut down shown in the Electrical Characteristics, TSHUTD.  It is always enabled.  The system should be designed to avoid the thermal shutdown since it would be unexpected operation for the system.