For low current applications, proper scaling of the current shunt resistor based on the total output current load helps reduce noise and improve accuracy.
Question:
The MAX17260 evaluation kit software looks like it has quite a bit of noise on the signal since it is showing the current vary from +3mA to -3mA or so. I have tested under many different scenarios (fixed current with a resistor, no connection, etc...) and I always see about the same widely varying current measurment.
Also I have tested this with both high side sensing, low side sensing and external current sense resistors... none of these seem to make a difference. What can I do to reduce the noise?
Answer:
At no load the noise level can reach +/- 3mA. It is 12-bit ADC, and register is 16 bit. The noise doesn’t degrade fuel-gauging accuracy because the long-term average is 0. When load current is higher, you should see that the average of this register is about 1% accurate. And if you look at the average offset current, it should be below 1mA. This is enough for fuel-gauging.
For noise improvement, customer needs to change the standard 10mOhm sense resistor to 100mOhm sense resistor, as this will provide better signal for lower range of load current scale.