Hi there,
I am using LMP8645 for a low-side current sense application as shown in the attached schematic. The current is a high-frequency diode-rectified unipolar current and I am trying to get the average of it. Therefore I have used an input filter.
1. The datasheet says that the input filter resistor can not be more than 10 ohm - is that for each input line? I have used 10 on each input line - is that ok?
2. The datasheet also says that the LMP8645 has an internal output buffer able to drive a capacitance load up to 30 pF or the input stage of an ADC. I am using the LTC1864 ADC, whose input impedance is not known to me. Is an output filter with 1k resistor and 180p capacitor as shown going to be a problem?
3. I am expecting to sense a max of 10A current, which means the common mode voltage will be -75mV. Therefore I am using Rg = 50k as per the datasheet recommendation. Is this ok?
4. The online error calculator on the product webpage shows more than 20% error for 1A sensed current. Could it be that bad? Please see the screenshot showing the values I put.
Thank you very much!
