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BQ27500/BQ27501 Fuel Gauge Current Montoring

Other Parts Discussed in Thread: BQ27500, BQ27510-G2

Considering BQ27500/501 for our new board to monitor the battery (Li Ion) that will supply the power to this board.  Based on the datasheets, the device will do what I need but I have a question...   The board will draw about 3A at peak but will draw about tens of uA when it is in sleep.  Can the BQ27500/501 monitor the battery state accurately for this wide current draw range?   If not then what devices you will recommend for my application.

  • Patrick,

    Those gauges will work find for your current range if you select the sense resistor appropriately.  You want the max voltage across the sense resistor to be less than the input range of the SRP/SRN pins, which is +/-125mV.  You will not be able to measure uA of current, but that is fine for our Impedance Track gauges since we will update the State of Charge (SOC) based on relaxed voltage measurements during this mode of operation.  With coulomb counting gauges you would not be able to measure this tiny passed charge although it could accumulate over time and cause a significant gauging error.  You don't have to worry about that with our IT gauges.

    However, I would recommend that you use a newer version like bq27510-G2 (if you want a QFN package) or the bq27520-G3 (if you want a chip-scale package).  These also do not require an external LDO as the bq2750x does.  They have more recently released firmware with all the latest algorithm improvements.