| ??? 06/06/09 09:29 Read: times |
#165895 - isolation Responding to: ???'s previous message |
Farshad Mohajeri said:
1) The horizontal design where both USB and RS485 ports are side by side, should be replaced by a vertical design where ports are on the opposing edges
2) The isolation gap between two grounds is not big enough I don't think these are really issues. There is more capacitive coupling in the optos than between the planes you have, and you can't really widen the gap beyond the distance of optos' pin rows. Farshad Mohajeri said:
3) Whole device can be powered from USB port, eliminating the EMI from power lines. (The reason that I didn't design it this way from beginning is that I wanted to isolate the PC from the converter as much as I can) This is the first thing I would do. Farshad Mohajeri said:
4) Place a ferrit-bead to filter power at USB chip VCC pin(s) Certainly. And 5V transils between the signals and the USB GND. Farshad Mohajeri said:
5) Reduce the copper in USB port area to the least possible area. Maybe, but not primarily. Farshad Mohajeri said:
6) Place the USB chip inside a faraday cage?
I don't think so. JW |
