XTAL startup issues on PIC 73B
D. Schouten email (remove spam text)
In one of my applications I'm using a PIC16C73B 20MHz part
running at 18,432MHz. The xtal is connected the standard way
i.e. with two 33pF caps (loadcapacitance spec of xtal is 32pF)
to ground and layout wise everything as close as possible to
the PIC chip.
The problem is that from the 1000 boards I test, about 25 aren't
running at all. Replacing the xtal usually solves this problem.
Sometimes the board works well in the pretesting phase, but fails
at the final test. Current xtal brand is TXC, but we've had similar
problems with other brands too.
My question is, is this 2.5% failure rate normal, or is something
wrong with my application?
Is the PIC16C73B sensitive in HS mode, or do I have to add small
resistance with the xtal, or large parallel resistance?
The application which has his problem is quite price sensitive, so
there isn't any room for varicaps or other tweaking stuff.
Thanks for any help.
See also: www.piclist.com/techref/microchip/time.htm?key=xtal
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