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BQ27GDK000EVM Programmable Load is Inaccurate

Ethan Williams
Prodigy 110 points
Other Parts Discussed in Thread: BQ27510-G3, BQSTUDIO

I am having difficulties with the programmable load on the BQ27GDK000EVM.  I'm controlling the programmalbe GDK load through the GDK section in bqStudio.  I have the BQ27GDK000EVM connected to an external EVM, the BQ27510-G3EVM, and a battery connected to the BQ27510-G3.  Everything is working correctly, as far as communication paths and other aspects of the software/board. 

The issue I'm having is using the GDK pluggin in bqStudio setting the discharging current.  The value I input to discharge at is off by a constant 71% when compared to the actual measured current, no matter what value I input.  For example, if I tell the GDK to discharge at 100mA, the GDK reports it is discharging at 100mA over on the left hand side pannel GDK box.  The fuel guage reports it's discharging at 171mA (the fuel gauge has been properly calibrated).  If I add in an ampmeter (I've tried two seperate amp meteres), it measures a current of 171mA as well.  (The fuel gauge reports 171mA with and without the amp meter in series).  This is true for any value I input within the range of 5mA up to 500mA (never tried anything higher).  The actual current drawn is 71% greater than the desired current.  

Is there a way to fix this issue?  Is there some calibration or offset for the GDK programmable load?

Thank you for the help. 

  • 0
    Prodigy 110 points
    Hello TI. I have yet to receive any support.
  • 0 in reply to Ethan Williams
    Intellectual 320 points

    I have a similar issue, but in my case, the current measured by an amp meter and the gauge is roughly 10% of the value it is supposed to be. For example, if I set a current of 2000mA, I measure a current of 270mA with an multimeter and the gauge measure roughly the same value. The GDK programmable load consists of a closed loop control circuit. Probing at the output of the DAC of the GDK board and I can see that the value changing when I change the current set point of the GDK, but the DAC output is erroneous and won't produce a correct load current. I suppose a firmware update will solve this issue, but TI does not seem to care looking at this problem. Where can we find help on this issue ? I wonder.