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bq20z65: Strange flags set

Nick56152
Intellectual 545 points
Other Parts Discussed in Thread: BQ20Z65-R1

I have successfully "programmed" and am running a bq20z65-R1 with a 3-cell LiPo battery pack (manually chose a CHEMID [thanks Jackie!], did the mandatory 2 cycle learning procedure and started the Impedance track algorithm by writing 0x21 to Man. Access).

Upon monitoring the gas gauge with bqEasy I noticed some flags set that just don't make sense (see screenshot):

Note: The circuit is being powered by the gas gauge controlled LiPo pack (i.e. no charger or external pack is connected).

The two flags that concern me the most are:

1. INIT and DSG are LOW.

From datasheet: "The INIT flag is always set in normal operation".

From datasheet: "0=charging mode, 1=discharging mode"

2. FET CONTROL: DSG flag

Shouldn't this be HIGH since the LiPo is discharging?

 

My LiPo-powered design seems to be working fine and is definitely NOT charging... so why are these flags set?

Are any of the other flag settings strange?

Note: The gas gauge circuit is identical to the bq20z65EVM circuit (i.e. two resistors used for precharging options not installed).

Thanks in advance to anyone who can provide some guidance! 

  • 0
    TI__Expert 3865 points

    Nick,


    Can you clarify the question?

    Both [INIT] and [DSG] are high as expected in BatteryStatus.

    [DSG] is set in FET Control register as expected.

  • 0 in reply to Jackie Hui
    Intellectual 545 points

    Sorry Jackie - for some reason for a moment I thought RED=low. Disregard the question :) All the flags make sense then!

     

    A final question/clarification though: 

    It seems that the [ST1CHG] flag is set along with [TR2a] - is this normal for discharging?

     

    Also, it seems this combination doesn't make sense after looking at SLUU386.

    pg9 and pg37 seem to contradict each other:

    pg37: TR2A temperature range uses ST1 charge voltage (which is what my screenshot indicates...)

    Good - but,

    pg9: Mentions the [Temperature Range] flags: TR1 to TR6 (i.e. no TR2A) -> Std Temp Charge 1 has flag TR3 set according to this page.

     

    Which is correct? Hopefully pg.37 (as this is what my gas gauge is indicating)!

     

    Thanks again for all your help.

  • 0 in reply to Nick56152
    TI__Genius 10235 points

    It looks like there is a slight discrepancy. Page 37 is correct. The table on Page 9 should not have TR6. TR2a (STCHG1) should be inserted between TR2 (LTCHG) and TR3 (STCHG2) and the table should end at TR5 (CHG suspend or inhibit).