Re: Re: Launchpad clock jitter: What should I expect?

"Reginald Beardsley pulaskite-/[email protected] [msp430]"
<[email protected]>: 

> Case of the xtal is grounded per spec.  Never mind hitting the xtal,
> just holding a finger close  (0.5 cm) to the xtal increases the jitter
> substantially.  If I put the scope in averaging mode and expand out the
> time base, I see slow oscillations in sync in the P1.6 trace and the
> trace from TEST.   Most of the noise on TEST cancels leaving a very
> small (~10 mv)  residual.   Without averaging the ringing on TEST is
> ~150 mV. 
> 
> That appears to confirm EMI as the source of the jitter.  In which case
> this is the best the board will do. 
> 
> Thanks,
> Reg

Maybe your scope lines also induce some noise...

Is there a solid ground plane below the xtal and the MSP430? This is a strong 
requirement for a stable clock. (in fact a continous GND it is a must for the 
whole board, you can not work with 2 layer boards today, except for very 
simple boards and wiring on one layer only).

Matthias



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Posted by: Matthias Weingart <[email protected]>
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