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bq34z100 FULLSLEEP Mode questions

john boehm
Prodigy 80 points
Other Parts Discussed in Thread: BQ34Z100

Hi

I am planning on using the bq34z100 as a coulomb counter for a 100 Amp Hr primary battery.   The load on the battery has a very large dynamic range, (50uAmps to 5 Amps).  The load spends 99% of the time in the very low current range (< 100uAmps) thus I believe the bq34z100 will spend most of the time in the FULLSLEEP Mode.

While in FULLSLEEP Mode will the bq34z100 continue to accumulate coulombs?

The specifications for the Integrating ADC (Coulomb Counter) in the data sheet for the bq34z100 gives a specification of 0.007 %FSR for the Integral Nonlinearlity Error.  Does that mean that the error for very small discharge currents (100uAmps) will be much larger than the actual discharge current?

Thanks

jib

  • 0
    TI__Guru 73830 points

    John

    The device does not enter Fullsleep unless you command it to do so. At 100uA, the device should not count any coulombs, because this will be below the deadband. The INL error is a function of the Full Scale Range of the current measurement and will be more noticeable for lower current measurements.

    Regards
    Tom

  • 0 in reply to ThomasCosby
    Prodigy 80 points

    Tom;

    I stated that the load spends 99% of the time in the very low current range (<100uAmps) because not only do I need to know what the bq34z100 is doing in this mode, but also because I need to minimize the current consumed by the bq34z100.  The bq34z100 draws 140uA while in Normal mode.   That would increase the load seen by the battery from 100uA to 240uA, which will greatly decrease my battery life.   My plan is to configure the bq34z100 to transition into FULLSLEEP Mode as soon as the load drops down to the 100uA level.  The bq34z100 should then only be drawing 19uA and only have a minor effect on my battery life.

    If the bq34z100 continues to accumulate coulombs while in FULLSLEEP Mode, then I need to understand the details so that I can account for any errors/noise etc.  If on the other hand the bq34z100 stops accumulating when it enters FULLSLEEP Mode, I can have my software calculate sleep time and sleep current and predict how much of the battery was consumed while sleeping.

    My question still is "while in FULLSLEEP Mode will the bq34z100 continue to accumulate coulombs"?    

    This conversation would work better if I had a number to call you at.

    Thanks

    John

  • 0 in reply to john boehm
    TI__Guru 73830 points

    John

    If the current is below the Deadband, then it should get included in the coulomb count in any state.

    Tom

  • 0 in reply to ThomasCosby
    Prodigy 80 points

    Tom;

    You have responded twice to this thread.  The first response indicated currents below the deadband would not be included in the coulomb count.  The second response indicated the currents below the deadband would be included.  I'm getting confused.

    Also, I have tried to understand the AUTOCALIBRATION paragraph on page 26 of SLUSAU1B and there are terms used that I can not find definition for ("Bus Low Time"  "Autocal Min Current" "Autocal Time"

    I would appreciate the phone number for an application engineer for the bq34z100.

    thanks

    John

  • 0 in reply to john boehm
    TI__Guru 73830 points

    John,

    I am sorry about the confusion. The previous response should read, "If the current is below the Deadband, then it should not get included in the coulomb count in any state."

    Please enter your biographical information on the e2e forum and we will try to arrange a phone call.

    Regards

    Tom