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bq20Z75-V160 / V180: BQ gas gauge does not have access to some registers?

Mike Wilson
Prodigy 215 points
Other Parts Discussed in Thread: BQ20Z70

Hello!

 I am using 4 cell lion, and my charger is pretty dumb (just a current source, no voltage limit).

I want to turn off the CHG FET at charge termination, which I was able to configure.

But I would also like to add turn off of CHG FET at "over charge fault".

SLUU265A, revised August 2007, page 101, Section C.4.6.2 Charge Fault Cfg (Offset 21) [OC]

is supposed to provide this functionality, if turned on. However, I cannot see how to access this using BQ Gas Gauge Evaluation Software version 0.9.59.

Am I just not looking in the right place?

 

Mike

 

  • 0
    TI__Expert 6470 points

    Mike,

    There are several bits under Configuration/OpConfig B in the dataflash that control how the charge FET is handled during faults. References to the bq20z70 here are the same for bq20z75. You can get help for any data flash parameter by right clicking on it and selecting "help text".

    CHGSUSP [7]: This bit enables the ability to turn off the Charge FET and/or Pre-Charge FET in charge suspend mode (See Charge Control Class).  

    ·         0 =  The Charge FET is unaffected by any type of charge suspension. 

    ·         1 =   The Charge FET and/or Pre-Charge FET are opened with any charge suspension.

    Normal Setting:  the default setting for this bit is 0.  It is common for this to be set to 1 to give the bq20z70 the control for additional protection.

     

    n       OTFET [6]:   This bit is used to configure how the bq20z70 controls the current FETs (Charge or Discharge) during Over Temp Chg or Over Temp Dsg faults.  (See Over Temp Chg and Over Temp Dsg)

    ·         0:  FET control is unaffected by any Over Temp Chg or Over Temp Dsg faults.

    ·         1:  During a Over Temp Chg fault the Charge FET will be opened.  During a Over Temp Dsg fault the Discharge FET will be opened.

    Normal Setting:  This bit defaults to a 1 which should be used in production for most applications.  Over temperature conditions can be dangerous and every level of protection possible should be used.

     

    n       CHGFET [5]:   This bit is used to configure how the bq20z70 controls the Charge FETs when [TCA] gets set in Battery Status.  (See TCA Set % for an explanation for when [TCA] gets set).

    ·         0:  Charge FET is unaffected anytime [TCA] gets set.

    ·         1:  Charge FET is turned off anytime [TCA] gets set.

    Normal Setting:  This bit defaults to a 0 which should be used in production for most applications.  Setting it to a 1 which would turn the Charge FET off is only  if Maintenance Current is set to 0.

     

    n       CHGIN [4]:   This bit is used to configure how the bq20z70 controls the Charge FETs when in charge inhibit mode.  (See Chg Inhibit Temp Low and Chg Inhibit Temp High).

    ·         0:  Charge FET is unaffected when in charge inhibit mode.

    ·         1:  Charge FET is turned off when in charge inhibit mode.

    Normal Setting:  This bit defaults to a 0 which should be acceptable for most applications.  It is important to note that this is different than charge suspend mode because this inhibits the charge cycle from occurring.  This function acts while discharging.