I'm considering substituting a crystal for a ceramic resonator in a USB project (12Mhz). I have a few of these to make, so using the 12Mhz crystals I already have would be nice. Is this possible simply by altering the capacitive loading? Anything to watch out for? As I understand it, this may overdrive the crystal. But I don't especially care about frequency - 500ppm is fine, so is this an issue? Many thanks.
Are you trying to replace a resonator that the mfr expects to be on the pins of the device?
Resonators and crystals have somewhat different operational modes, and the on-chip oscillator may not work with a crystal. If you have the details of the onboard oscillator (from the datasheet or perhaps in an app note), I would run it by the group (perhaps on a.b.s.e).
I wanted to do this (on a USB hub device), but my crystal supplier stated quite unequivocally that the onboard oscillator required a ceramic resonator and they had no crystal that would work as is. By altering the loading and perhaps providing a DC feedback path (100k or so in parallel with the crystal) things *might* work, but it will depend on the implementation details of the oscillator.
Cheers
PeteS
What's the oscillator ?
Most chips will use resonators or crystals equally happily but the capacitive loading may have to be altered ( see the crystal / resonator mfr's datasheet and the semi makers too ).
Graham
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.