I would like to use the ADA4528 opamp or similar opamp to monitor current consumption across a sense resistor for an IoT device but with a Caveat. I want to measure the entire range with one setup/setting
Project: To create a current sensing instrument that I can use to plot the entire Transmission window of a battery power IoT device. To this far iv used different tools on the different current setting and then I add it all up afterward. This is time-consuming and often think small energy savings made in code is not visible due to set up at different current levels.
Parameters: Range required is from 1uA to 200mA (I would like to get nA). System to be powered via USB. so max supply for OpAMP will be 5v unless boosted but would like to avoid if possible. Only DC currents to be measured.
The first thought and one of the questions. if A low tolerance thermal stable resistor is used like a 0.1R is it even practically possible to measure nA at a current of 1uA over that resistor or would other factors dominate.
Second thought, if my first thought is unfeasible then how about a compensation system. Most IoT devices run at 3.6V or lower. So using a 5v LDO or switching setup to step down as the supply. Will it be possible to use a higher value sense resistor like 1R and when the current gets close to the 100mA to 200mA mark the feedback pin of the LDO would tell the PSU to compensate for the voltage drop across the resistor to keep the system voltage stable.
If this could work it will allow the output to be fed into a scope or ADC and record the entire event as a single test. Maybe an entire Soc like the ADS8681 could be a nice solution
Thanx in advance