# How to calculate if I need to buffer the input to my ADC?

I am putting the output of a current sensing IC (ACS70331) into an ADC (LTC2373). I am that a buffer on the input to an ADC is often required if the output of the source is high impedance. However, I am not sure how to find the cutoff where that becomes necessary for the ADC and I do not see the impedance on the current sensor data sheet.

I have some guesses that you could look at the source current (0.4mA) of the current sensor and calculate the dV/dt of the input capacitance of the ADC input. I am looking for confirmation if that is the proper approach for this type of problem.

• Generally the correct approach yes. Oct 30, 2020 at 18:14
• @Andyaka How would I know what is "fast enough" for the dV/dt? The ADC samples at 1MS/s, if I am expecting a 2V signal should I be able to hit that point in a single sample? So 2V/us? Oct 30, 2020 at 18:44
• The devil is in the detail for sure so try using a simulator. Oct 30, 2020 at 18:47
• I am looking for confirmation if that is the proper approach for this type of problem. - my comment is not a full answer because that is not what you asked for. Oct 30, 2020 at 18:48