I am making a new PCB where size and weight are critical. I would like to drive two chips (a microcontroller and a Bluetooth chip) using a single crystal oscillator. What is the effect of driving several chips with a single oscillator? Is it possible?
Oscillator: Abracon AP2S oscillator -
Thanks
So long as it is the same frequency, or multiple thereof, why would you think it is not possible? Am I missing something?
Tam
new PCB where size and weight are critical. I would
I'm wondering if the input capacitance of the chips affects the oscillator. The oscillator has an optimal load capacitance that it performs with. I can't seem to find the input capacitance information in the datasheets of the dsPIC or the BT module.
Sure, but make sure that both chips get clean, fast edges, which means that you've got to handle the trace routing, impedances, and terminations properly. Even cheap XOs can have sub-ns risetimes these days, and lots of cmos chips have very tender clock inputs. A little ringing, or a half-level plateau and a bit of crosstalk, can cause serious grief.
John
new PCB where size and weight are critical. I would
That information should be there, buried in the 100s of pages of other necessary information.
By the same token, though, if you can't be sure that two will work, how can you be sure than one will?
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html
If the oscillator has a logic level output, it will work with any load within its fanout limits. If you are using the oscillator built into one of the chips, and you want to use its output to drive the other chip, I would put a gate of some kind near the source chip to buffer the output.
Tam
new PCB where size and weight are critical. I would
use a couple of unity gain stages to drive and semi isolate them.
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
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