When a 10 mOhm sense resistor is used, the LSB for current is 0.15625mA and the LSB for capacity is 0.5 mAh. For a 20,000 mAh battery, the translated value should be 40000 integer, or 0x9C40, which is higher than 0x6000, and shouldn’t be used. To get around this, there are two options:
- Use a 5 mOhm sense resistor.
- This option is not recommended due to the low current usage mode. With a 5 mOhm RSense, the 0x4E20 programmed capacity is fine, but the input to the current measurement is half the burden voltage as a 10mOhm sense resistor. For best coulomb counter performance, the sense resistor should match the current range of the application, and a 10 mOhm is a good fit for the discharge levels of this application.
- Use a CGAIN value to scale the currents/capacities digitally.
- If a CGAIN value of 0x0200 is used, it will still measure all currents on the higher dynamic range with the 10mOhm R_Sense, but the digital values will be scaled, allowing a 20,000 mAh battery to be used. If CGAIN = 0x2000 is used, the LSBs change to 0.3125 mA and 1 mAh.