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BQ27Z561: Coulomb Counter conversion time vs ADC conversion time

Groupe-HW
Prodigy 50 points
Part Number: BQ27Z561

Tool/software:

I see in the datasheet the conversion time t(CC_CONV) for the coulomb counter is 1000 ms typ while the ADC conversion time t(ADC_CONV) is 11.7ms typ.

Also, regarding the paragraph 7.3.2.2, I see "New conversions are available every 1 s."

Could you confirm the coulomb counter ADC converts the voltage difference accross the sense resistor only 1 time per second ?

Or it converts several time in one second and gives processed conversion results every second ?

  • 0
    TI__Mastermind 37761 points

    Hey Sebastien,

    The ADC converts once per second, and the gauge reports the value once per second

    Regards,

    Nick Richards

  • 0 in reply to Adrian
    Prodigy 50 points
    Hi,
    We've planned to use BQ27Z561-R2 fuel gauge solution for one of our products. However, the product operation imply enabling a 2A load with a 10 Hz PWM (duty cycle from 10% to 100%, so the ON-time will be between 10 ms and 100 ms).
    In the BQ27Z561-R2 datasheet, we can see that the conversion time is 1000 ms. Does the fuel gauge integrates current measurement over 1000 ms, or does it takes only one measurement ?Say otherwise : if we use a 10% PWM (10ms ON, 90ms OFF) on our 2A load, assuming 0A consumed on OFF time. What will be the measured current ?
    • 0A or 2A, depending on when the samping arises ?
    • 0.2A, averaging the measurement on 1000 ms ?
  • 0 in reply to Groupe-HW
    TI__Mastermind 37761 points

    Hey Sebastien,

    The ADC takes one measurement per second on this gauge. Since the load is on for a short period and happens frequently over a period of a second, the gauge will miss the majority of these current pulses. So in terms of the current coulomb counting, this will be inaccurate. However, the gauge will still be able to take accurate voltage readings.

    Regards,

    Nick Richards