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Original question:

BQ4050: Coulomb Counter

BQ4050: Questions from datasheet

Arkadi shap
Intellectual 660 points
Part Number: BQ4050

In the datasheet (bq4050), section 7.3.6.1 is written - " The fundamental rate of the counter is 0.26nVh". is it the threshold voltage (0.26nV) for the sense?
In the datasheet (bq4050), section 8.2.2.1.4 is written - " The device is designed to support 1mOhm to 3mOhm sense resistor"
As i wrote before, my discharge current is 100uA. If i use 3mOhm, The sense voltage would be 300nV. 
Would the bq4050 be able to sense such a voltage?

Another question- 
section 7.4 - In the Normal mode the date updates every 250mS intervals. what dows it means about the coulomb counter? does it continuous monitoring and accumulating the charge?

  • 0
    TI__Mastermind 42535 points
    No, that's the rate of the internal coulomb counter. You're mistaking calibration values for sensing values. The device will not support such low discharge currents. We need a minimum current of C/10 for accurate gauging.
  • 0 in reply to Batt
    Intellectual 660 points
    Thanks.
    How do you calculate this (C/10)? Where can i see it on the datasheet?

    Do you have any BMS devices that may support such a low currents?
    (I didnt find, but i suppose there should be)

    Regatds,
    Arkadi
  • 0 in reply to Arkadi shap
    TI__Mastermind 42535 points
    C/10 is a rule of thumb we use with our gauges since it's 10 times that of quit current and for a 1000mAh cell it's at or above dsg threshold in the gauge. Unfortunately we don't have any gauges that support sensing currents in uA.
  • 0 in reply to Batt
    Intellectual 660 points
    Hi,
    Thank you for your answers, but I dont understand something:
    Typical Rsense, as it is written in Datasheet, is 2mOhm. 2mOhm tims current of ~100mA (C/10) is 0.2mV.
    I can get this voltage for 100uA by increasing the Rsense to 2 Ohm (2Ohm tims 100uA = 0.2mV).

    I read your answers with a lot of attention, but I still dont undarstand why i cant increase the Rsense (as i wrote above)...

    Do you have a datasheet or some file that describes the chosing of Rsense? Or do you have some calculation of Chosing Rsense?
    It doesnt make sense to me that TI doesnt have some file about it...

    Regards,
    Arkadi