I am confused about the acquisition time specification for the AD7470 - it's given to be 135ns. My understanding of ADC is that the acquisition time is related to the settling to 1LSB of the sampling circuit. The circuit given in the data sheet for the sampling circuit has a time constant of a few [ns]. So for 12-bits converter will require appox. 8 time constants for 1LSB settling which would be of the order 40[ns]. Can someone explain where the 135[ns] is from? Thank you.