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BQ27500

Steven Carter
Prodigy 140 points
Other Parts Discussed in Thread: BQ27500-V130, BQ27500

I have a BQ27500-V130 Fuel Gauge in my design.  

The BATT-LOW signal is connected to a MSP430 (GPI).  This signal does not toggle when the battery capacity goes below the set threshold.

I have set SOC1 Set Threshold to 200mAh.

My battery is fully charged and the SOC1 remians low - as seen in the FLAGS register.

I then flatten my battery to 150mAh capacity.  The SOC1 FLAG toggles to HIGH but when probing the BATT-LOW pin it does not change and remain low.

Are there any other controls I need to send to the BQ27500 to enable this functionality?  I discharged my battery separately to my unit and re inserted it when it was low.  Could this of had an impact?

I would appreciate any feedback

Thanks

  • 0
    TI__Expert 4050 points

    Steven,

    what is your pack configuration setting? When this happened, is the gauge stand alone or connected to the MSP430?

    Thanks

    Ming

     

  • 0 in reply to Ming Yu
    Prodigy 140 points

    Hi Ming,

    I have a 3.7V Li Iion Single Cell battery pack.  The Batt Low signal goes to a MSP430 (Input) and it also goes to a STM32F103xxx processor (ST Micro) and that is also set up as an input.  There are no external components on the BATT LOW line such as pull up resistors. 

    This is the first revision of my design and I have not been able to get the BATT LOW signal to toggle at all - even though the SOC1 bit in the FLAGS register is toggling as expected.

    I am not in the office again until Tuesday so I am not able to access any more detail until then. 

    Does this information help?  If you want anything more please let me know.  Currently we have a software work around in our system for this which involves polling the fuel gauge for its capacity but this is not preffered due to power consumption requirements of our system.

     

    Steven Carter

  • 0 in reply to Steven Carter
    TI__Genius 14985 points

    Steven,

    We need to check how you have configured the BAT_LOW pin.  Can you tell us what the Operation Configuration register is set to in your DataFlash screen (Configuration tab)?

    See page 25 of the datasheet.  The simplest way to use the pin is for the [BATL_CTL] bit to be 1 to enable the BAT_LOW pin to follow the [SOC1] bit in RAM.

    The OpConfig register would have been set when you went through bqEASY step 2 depending on the answers to the questions, but you can manually modify the dataflash afterwards.  Try to click on the Op Config value, type the new value, and hit the enter key to update that item in the ICs dataflash.  You can also click on the work "Op Config" to see a pop-up showing the individual bit values.

  • 0 in reply to dMax
    Prodigy 140 points

    Hi David,

    That is it, I have it working now.  I was using an older data sheet for the V120 (i think - SLUS785D April 2008) and this bit was not in the register.  I have updated to the latest data sheet and all is good.

    Thanks for your feedback

    Steven Carter