I have a PIC32 project (PC scope and analyzer) that requires USB isolation 
(power and data lines) with a dual supply for opamps used as a front end to 
an ADC. I think I have managed to find a reasonable solution, but I would 
appreciate any views from others as to how they might go about it.

 The reason for not using single supply opamps with level shifting is that 
it makes maintaining a constant impedance difficult. My current idea is to 
use an ADuM4160 with a +5 to +/-5V isolated DC to DC converter, followed by 
three LDOs, +3.3V for PIC32 and +/-3V for ADC and opamps. I will use the 
+3.3V for the ADC digital out also.

Also what do people think about using the OC for the ADC clock? My feelings 
are that it is not ideal (jitter, etc), but for a cheap (I'm trying to keep 
the component/final cost down) PC scope it should suffice. I tested a basic 
prototype (ADC and PIC32) using this and it seemed to work okay. I am also 
looking at a version based on an FPGA, with DDS for ADC clock, but that 
would be a entirely different beast.





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