The circuit below is from this App Note.
The document describes:
The capacitors C1 and C2 need to fully charge for the circuit to function properly. The definition of fully charged can vary depending on the accuracy required for the circuit. If we assume a 12 bit system the time required to fully charge the input capacitors is given below.
For 12 bit settling
τ1 = R1C1 = (1kΩ)(10μF) = 0.01s
T1 = ln(2^N)τ1 = ln(2^12) (0.01s) = 0.083s
In the second picture, when the switch is open R1 is about 63k. I want to understand better what really happens here when I use this circuit connected to an ADC. In my case I have a 12 bits ADC, so:
τ1 = R1C1 = (63kΩ)(10μF) = 630ms
T1 = ln(2^N)τ1 = ln(2^12) (620 ms) = 5.24s
5.24s is way too long. Does this mean I wouldn't sample the signal correctly until the capacitor charges in ~5s?