[SI-LIST] : Connecting board grounds to chassis

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From: Pessotto, Michael (michael@doctordesign.com)
Date: Mon Nov 06 2000 - 20:40:35 PST


In a PCB with audio and video outputs referenced to AGND and digital outputs
referenced to DGND what is the best way to connect the board grounds to the
chassis? In our current design we have chassis connected to DGND through the
digital output connector shells and through standoffs between board and
chassis. The analog output connector shells are tied to AGND and are
insulated from chassis. When we went to FCC pre-scan we saw the cables
connected to AGND radiate with peaks corresponding to the clock frequencies
used in the digital section. Shorting the analog connector shells to the
chassis eliminated these peaks but introduced the noise from the digital
plane onto our analog outputs. I thank you for your help in advance.

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