i am planning a circuit and was wondering if i could use shunt resistor to measure current consumption whithout amp and jsut use MCUs Vref input as is shown in the attached circuit diagram. The current i willll be sensing is 100mA to 2A and Rshunt = 0.01 Ohm. So at I=100 mA, Vsens would be 0,001 V and at I=2 A, Vsens would be 20 mV. So in total at max current the powerloss in shunt would be around 40mW, which is important since whole thing is battery powered. The load is max 10W. The ADC is 12bit so it has 0.24 mV step, so the resolution of read should be fine. I can also change ADC to a 14 or 16bit if i will have to.
Would it be a better idea to go for lower shunt resistance of 5 mOhm or even a 0.1 mOhm, to reduce powerloss and going whit a 20 bit ADC or even higher?
Thanks for any help in advance.