Re: Adding a crystal to a 20b or 30b Message #2 Posted by Eric Smith on 11 May 2011, 6:21 a.m., in response to message #1 by Marcus von Cube, Germany
10 pF is in the right ballpark. 15 nF is three orders of magnitude too much! I guess since they're not actually using it in the calculator they didn't double-check that they specified the right value on the schematic.
It is somewhat tricky to determine the optimal value to use because it depends on the capacitance characteristics of the chip, the crystal, and the PCB layout. 32kHz crystal oscillators can be particularly finicky compared to more traditional crystal oscillators (e.g., 4-20 MHz).
Edited: 11 May 2011, 6:29 a.m.
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