I am currently designing our SO-DIMM audio ADC module around the AK5397EQ analog-to-digital converter. Since most analog inputs will be used in mono mode instead of stereo, I am very tempted to design the module as a pair of mono channels, with one ADC converter on each side of the SO-DIMM board, and a ground plane in the middle. This will give us an extra 3 dB of SNR.
Following the thorough design of the AK5397EQ Evaluation Board, each mono input buffer will be driven by a set of three LME49990 operational amplifiers, which seem to be even better than the AD797 that I have used in earlier designs.
From a power supply standpoint, the evaluation board uses only 3 power regulators, instead of the 11 found on most designs based on the ES9102C. I will follow this approach initially, which means that we will need a total of 6 power regulators for every module. But I have yet to decide where they will be mounted.
One option would be to use card edge connectors on the backplane, as explained on this earlier post. But this would increase the amount of PCB real-estate that will be used on the backplane. Another option would be to take advantage of the fact that our SO-DIMM boards will be sparsely populated for the ADC modules, unlike the DAM ones. With that in mind, we might be able to mount the power regulator boards on the SO-DIMM board itself, with 3 regulators on each side of the module. I’m just not sure which connector should be used for that, and whether this is really worth the effort.
Initial design to be posted tomorrow…