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BQ76930: BQ76930

GURURAJ TALEWAD
Intellectual 445 points
Part Number: BQ76930
Other Parts Discussed in Thread: TIDA-00449

Hello TI team,

Design Guide: TIDA-00449 10s battery pack monitoring, balancing, and comprehensive protection, 50-A discharge reference design.

In this design what will be Pack+ voltage wrt Pack-. when only DSG MOSFET is OFF. 

  • 0
    TI__Guru 54715 points

    Hi Gururaj,

    It will depend on the load on the PACK terminals which may include the meter.  With the DSG MOSFET off PACK- is not held down.  CHG is driving to about 12V nominal, the resistors to the gate and the gate-source resistor will pull PACK- to about 12V with no external influence.  So with a high impedance the PACK+ wrt PACK- is likely about 12V below the battery voltage. 

    As soon as you attach a meter, the meter likely has a 10M input resistance which creates a voltage divider with the 1M typical resistance in the CHG circuit path as well as the reversed gate-source zener which is then forward biased.  The light load will try to pull CHG above its normal output toward its clamp voltage.  So the voltage the meter measures will be somewhat less than  the (Vbattery - 12) V.

    If you turn off the CHG output also the CHG output pulls down to GND with about 1M, see the data sheet parameter.  It will again create a voltage divider.