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BQ76940 reading issue

Han Zhang52
Prodigy 20 points
Other Parts Discussed in Thread: BQ76940, BQ76930

Hi guys

I am working on BQ76940 and got a problem with i2c reading.

I was trying to read data from registers. I wrote 0x19 to the CC_CFG reg(0x0B) first (verified by reading it ), connect 13 voltage sources to the pins and shorted some pins as the datasheet mentioned.

then I tried to read all the register values, that's when I met the problem. I can only read out the first five cell voltage, the rest are just 0x00, 

Did I make any mistake by doing these? Please offer me some help.Thanks

  • 0
    TI__Expert 6085 points
    hi Han, I have noted such problems, if the VC5X is down or the upper cell are below V_shut.
  • 0 in reply to Vish Nadarajah
    TI__Expert 6085 points
    Han Zhang52 replied to BQ76940 reading issue.
    Hi Vish,
    Thanks for reply, do you mean that I should pull down VC5X to GND through a 10K resistor as the datasheet mentioned?
    Thanks

    ------------------------------------------------------------
    answer]
    VC5CX is the reference for bank of cell VC6-VC10. typical VC5X = VC5 - V(diode). In bq76930/40 based design, VC5X is also used as a gate voltage source in a FET ( source follower) configuration to power the REGSRC. also make sure, the cell connection table 8-3 is followed for 13 cells using bq76940