Q
I\'m going to use AD9240 in my project. It would be interesting to know, do
a SINAD parameter (in data sheet it is 75dB @ 5MHz) include an aperture jitter
influence, and how well an aperture delay matches from part to part.
A
The SINAD parameter includes aperture jitter due to the circuits internal to
the AD9240. It is assumed that the external sampling clock jitter is negligable
compared to the aperture jitter of the device.
SINAD is an observed measurement which takes into account all the non-ideal
features of an ADC - there is no way to "turn off" aperture jitter, INL/DNL,
digital feedthrough, modulation of the clock by the input signal etc. We take
all possible applications measures (outside the chip) to reduce such effects to
a minimum (good grounding and decoupling, clean sample clock, careful layout,
minimal load on the digital outputs etc etc )
The aperture delay is only a typical specification and I have no way to judge
the variance from part-to-part of this parmeter. If it is critical in your
system, you should take measures to compensate for the difference in aperture
delay between parts e.g. calibration. In any case, you may have to compensate
for different group delay in the circuitry which drives the ADC (filters and
amplifiers)
