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CN0510/AD5941 Loss of accuracy after amplifying disturbance current

Hi, I'm using the CN0510 to measure a single 18650 lithium battery.

For some purpose, I need to amplify the sense current to 2A maximum from the Darlington pair of CN0510.

The schematic of CN0510 is here:


After I replace the emitter resister which is named R21 in the schematic, and the value is 62Ohm, into 4.8Ohm,

the current flow out from the battery increase from 23.835mA(mean) and 11.062mA(peak-peak) to 269.86mA(mean) and 133.81mA(peak-peak).

This is the same as circuit simulation.

The actual waveform is like below, and the channel configuration is in the picture,

R21=61Ohm waveform

R21=61Ohm Vdc=3500 Vpp=300

R21=4.8Ohm waveform

R21=4.8Ohm Vdc=3500 Vpp=300

It seems good but after I open the terminal such as Putty, the result from CN0510 gets strange.

When I use 62Ohm as R21, the impedance of measurement is like the lithium battery impedance theory as below:

R21=61Ohm EIS

But after the 4.8Ohm resistor installed, the result is distortion:

I'm wondering if the current is too large so the input stage of AD5941 gets over the range.

So I measured the AIN2 pin and AIN3 pin after AD8694, the voltage is like below:



Is this value over the range of the AD5941 input stage?

Or there is something I missed, so I can get the right value of EIS of lithium battery?

Thanks for your apply, hope you have a nice day Slight smile