A crystal is a high Q circuit. You can't pull them much. I think your first idea about yanking the crystal and just driving the pin is a better idea.
If the part has a shutdown feature, it would pay to determine the state of the crystal input pins when in the shutdown mode. -----Original Message----- From: "Don Latham" <d...@montana.com> Sender: time-nuts-boun...@febo.com Date: Sat, 5 Mar 2011 02:06:18 To: time nuts<time-nuts@febo.com> Reply-To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: Re: [time-nuts] pulling oscillators Hello all: I've developed a need for pulling crystal oscillators built in to pll circuits. These are cmos, and have the common style oscillator circuit built in. The crystal is across an inverter in the chip, and there is a small cap between each end of the crystal and ground. The chips are pll's in radio transceivers, early at that. I could carefully remove the crystals and caps, simply driving the non-inverting input on the chip with the reference, but I would rather simply tack on a very small cap and "pull" the crystal oscillator with an external reference signal of the right frequency. Anyone out there tried this? Thanks Don -- "Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind." R. Bacon "If you don't know what it is, don't poke it." Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.