What shunt capacitors do you have from each crystal lead to ground?


At 09:54 AM 10/14/97 -0700, you wrote:
>Have a problem with a circuit occasionally oscillating at
>3X the crystal speed.  It is a DTMF decoder IC (Motorola MC145436) directly
>connected to a parallel resonant crystal with a 1M resistor in parallel.
>
>Thought it was a problem with a specific brand of xtal, but another brand is
>doing it too.  The oscillator may start up fine and be on freq, but other
times
>it doesn't.  If it does start fine, I can 'force' it to go 3X by momentarily
>touching the
>PC traces for the xtal.
>
>Does overdriving an xtal cause it to oscillate at 3X?  Perhaps I need to add
>a series
>resistor?
>
>PCB is spotlessly clean.  Traces are short and fat.
>Any help/insight is appreciated.  Thanks
>Dave
>
>
---------------------------------------------------------------------------
Lynn Richardson - Design Eng.|WA0ZNL            |Progress Instruments, Inc.
DC - 1GHz, RX, TX 100W, PLL  |WA0ZNL.AMPR.ORG   |807 NW Commerce Drive
ASM 6805, 8051, Z8, PIC      |44.46.176.3       |Lee's Summit, MO 64086
C                            |lrich@proginst.com|P(816)524-4442 F 246-4556