MCF5282 Oscillator/PLL

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MCF5282 Oscillator/PLL

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ScottEZ
Contributor I

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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TomE
Specialist II

See if anything in this article helps:

 

https://community.freescale.com/thread/110134

 

Check the power suplly filtering to the PLL. If there's noise or voltage variations on the PLL supply it could explain your problem.

 

Tom

 

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