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I am currently designing a high speed (50+ MHz) mixed signal board =
that is used in a larger multimodule system. There are a number of both =
A/D and D/A Converters on the board with two distinct areas of analog =
and digital processing circuitry. We are able to maintain pretty good =
physical isolation between the IF analog block and the high speed =
digital signal processing block. I am looking for some input on how to =
handle the power and ground structure of this board to maintain the =
signal integrity of the analog circuit. We do currently have separate =
analog and digital power supplies available. =20
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There are three main areas of concern. =20
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First, how do we best handle the ground boundary between the analog and =
digital circuits given that we have multiple ADCs and DACs straddling =
this boundary? Should we use one solid GND plane? If not, how should =
they then be tied together (if at all?) to avoid gound loop issues? =20
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Second, how should we handle the board ground relative to chassis=20
GND. Should we tie the analog GND, digital GND, or both to chassis GND =
on this board or should the only connection to chassis GND be at the =
power supply?=20
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Third, within the analog circuit, we have isolation concerns between =
high and low level analog signals. We are looking for the best power =
supply filtering solution (ferrite beads?) which will allow us to better =
isolate the sections of the analog circuit from each other.
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Thanks
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Chris Roberts, Telecom Analysis Systems
[email protected]
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