Scott Zimmerman

MCF5282 Oscillator/PLL

Discussion created by Scott Zimmerman on Apr 30, 2012
Latest reply on Apr 30, 2012 by TomE

We're having startup problems that appear to be related to the oscillator or PLL within the MCF5282. It's set for "normal PLL mode with crystal reference", using an 8MHz crystal multiplied by 10 for 80MHz system clock. I see excessive clock jitter - enough to effect other circuit operation, and sometimes the SYSCLK drops out after a few seconds after power-up. Replacing the crystal with an external 80MHz oscillator seems to fix this issue... but easier said than done on an existing design.  Replacing the processor itself also - sometimes - fixes the problem. 

 

Has anyone alse seen this problem?  Everything is pointing to an oscillator/PLL problem within the MCF5282, but so far nothing is acknowledged from Freescale.

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