RE: Blog #3: High-side, Low-side and Low current sensing

michaelkellett — Tue, 24 May 2022 08:58:34 GMT

From your test results the difference between the measured current for high side and low side sensing is about 0.7mA which corresponds to a voltage across the 10mR sense resitor of 7uV.

The change in common mode voltage is 10V.

So the chip is giving a common mode rejection of 7uV/12V - 20 * log10(7e-6/12) = 124.7dB.

The worst case spec for the chip is 123dB so it is possible that ALL the error comes from common mode rejection.

But also bear in mind that 0.7mA change in current is equivalent to a change of 33 * 0.7/335 = 0.07 ohms in the load - are you sure that the plugged wire connections on the breadboard are that good ?

RE: Blog #3: High-side, Low-side and Low current sensing

colporteur — Mon, 23 May 2022 16:23:38 GMT

Great tutorial. It would of saved me a lot of time doing research for my challenge.