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BQ 76940 cells voltage read from I2C are zero

Huang Hung Yau
Prodigy 10 points
Other Parts Discussed in Thread: BQ76940

Hello,

I am using the BQ76940 to design the 14S BMS. I have one problem.

I gave volts and time sequence to TS1 pin to shift it from ship mode to Normal mode.

Sometimes i'll get 14S cell voltage and offset value is zero from I2C until setting command enter ship mode. 

Wait few seconds, Retry again(ship mode  to normal mode)will enter Normal mode , Then checking every registers values are right. 

This situation not always happen(1/100), but it's very confuse to me. Could you give me some way or suggestions to me.

and support some time sequences, flow char or application notes about entering BQ76940 ship mode and normal mode.  

Thank you

  • 0
    TI__Guru 54715 points
    Hi Huang,
    Check connection of your TS2 and TS3 resistors. If the part has a residual voltage on TS2 or TS3 it will not start properly and will show an XREADY error with no voltages. There are several questions on the forum about this. Even if not using a thermistor connect a 10k or similar resistor from the TSn pin to the appropriate reference.