Hi,
It may look stupid. I am just wondering will the reference voltage affect the sampling speed? In order words, can a ADC at Vref=2V has the same sample rate as the ADC at Vref=3.3V?
I think it will not affect the speed, only operating frequency and resolution of the ADC do. Correct me if I am wrong.
I can't think of a reason that VRef has an influence on max sample rate.
But if there is an issue or relationship you surely will find the information in the datasheet. Either as text or as a chart.
Klaus is correct. There may be be issues with the slew rate and output impedance of circuits providing the voltage to the ADC input but from there onward the sampling rate is only dependant on the type of ADC and with the exception of flash converters, it's clock rate. Vref only changes the full-scale voltage the ADC can measure up to.