ADC12J4000 Sampling Aperture Time

Cagri,
Per the datasheet, pg.14, the aperture delay (time from clock edge to sampling instant) is 0.64ns typ, and the aperture uncertainty (jitter) is 0.1ps rms.
Regards, Josh

I understand "time from clock edge to sampling instant" like that we apply pulse and ADC starts sampling after 0.64ns. But according to your comments "time from clock edge to sampling instant" is pulse to starting hold time.
As an additional question i need low sample rate (1MSPS) but very low aperture (lower than 1 ns) ADC is there any suggestion about that ?

For data converters with sampling rates <= 10MSPS, I recommend posting your question in the Precision Data Converters Forum to get the attention of engineers more familiar with your request:
e2e.ti.com/.../precision_data_converters

Dear Josh,
I am working with cagri in the same project. We want to learn: What is the duration of sampling instant? I mean that duration of reading data from input signal in one sampling.

Ahmet and Cagri,

It is true that the sampling switches in the S/H require some amount of time to turn off and trap charge, so the process of trapping the signal charge does not occur instantaneously which results in a window of time during which the sampling process occurs. I believe this is the information you are asking about. The aperture delay reported in the datasheet is a combination of this charge trapping time and the propogation delay of the clock path from the clock input pins to the sampling switch and the delay through any buffers at the analog input. Unfortunately, we do not typically characterize the charge trapping time and other delays separately, so I cannot go into more detail. It is likely that the charge trapping time is highly dependent on PVT and the input clock frequency and edge rate, though I do not have data.

Regards, Josh

Josh,
Ok then another question, if the aperture delay is 0.64 ns, how has the ADC 4000 MSPS sampling rate? It should be about 250 ps, shouldn't it?

Ahmet,

Aperture delay does not necessarily limit sampling rate. As I mentioned before, the aperture delay is composed of a number of delays: The charge trapping time (let's call it sampling aperture), the clock path delay, and input signal path delay. The sampling aperture time would definitely limit the sampling rate (because the speed of the switches to turn on and off will limit the overall switching rate). The clock path and input path delays only skew the sampling instant relative to the input clock edge - they do not limit the switching rate.

Regards, Josh