I am trying to isolate my AD7794 converter from my microprocessor using the ADUM5010 and ADUM1311 isolators. The isolators would be placed on a separate board, which would be linked via a flat cable to the processor board and ADC board. This way I can easily implement both the isolated and non isolated solution just by replacing the connection cable.
Since my application is in an EMI sensitive environment, I have some concerns about this. Besides standard PCB design measures, I am considering implementing some simple form of shielding, which is very briefly mentioned in the application notes. My questions are:
- is wrapping the isolation board with conductive tape a good idea?
- if I use a metal case, should it be feromagnetic, or is copper also fine?
- should I ground the shield? If yes, should I ground it to primary or isolated ground?
- if I implement shielding, would this compensate for the drawbacks of using a double layer PCB?
we did some EMC testing (radiated immunity) on some of our parts (AD7192 and AD7780). The application notes (AN-1186 and AN-1187) are available on the AD7780 and AD7192 product pages.
When performing the testing, the AD7780 and AD7192 were used as part of a weighscale design. However, the app notes have alot of general information which should also be appropriate to your system (using a common gnd plane on the PCB board, placement of components about the ADC, etc).
We tested the systems with a copper shield also and this improves the performance considerably. Using a copper shield with your 2-layer board should compensate for your 2 layer board. The shield does need to be grounded to the local ground of the PCB board. So, in your case, each board has its own ground that should be used as the shield connector i.e. each board will require a separate shield.