The real issues are the sharpness of the waveform and ringing, i.e., harmonics. An RC network on the output will suppress the harmonics on the signal trace. In addition, power to the osc must be isolated with a ferrite bead and cap to prevent contamination of the power bus.
> ---------- > From: Mike Mayer[SMTP:[email protected]] > Reply To: Mike Mayer > Sent: Wednesday, July 22, 1998 9:29 AM > To: [email protected] > Subject: Re: X-TAL oscillators > > =I've come across a board that radiates badly, the source appears to be > the > =oscillator itself.... I managed to drop emissions by increasing the X-TAL > =resonant caps from 47pf to 150pf. All waveforms still looked fine. > = > =Any suggestions on what could be happening, and thoughts on the best ( ie > =quietest ) X-TAL configuration to run at 20 MHz would be appreciated. > = > =Thanks, > = > =Derek Walton > =Owner: L F Research EMC Design and Test Facility, Poplar Grove, IL. > > Even one step back -- some devices allow connection of a crystal or an > oscillator. Does anyone have any idea which would have lower > emissions? I've seen oscillators recommended, but I would think > crystals would be better (given same frequency/package). > > -- > ========================================================================== > === > Mike Mayer Artesyn Communication Products, > Inc > Madison, WI > http://www.artesyn.com/cp > ========================================================================== > === >
