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PLL / DLL clock unstable at -10C

Question asked by Phuong Doan on Nov 7, 2011
Latest reply on Dec 2, 2015 by dank4

Hi,

 

I am trying to debug an intermittent boot up failure starting at -5C degree in our production system with using MPC8270. During the debugging, we find out that when the system failed to boot up at -10C, the DLL output is jumping and very unstable which causes the corruption of the load/store instructions to/from SDRAM.

 

In our system, we have the clock configure mode as PCI agent mode with the PCI clock (66MHz) feed into the clkin1 (as figure 10-2 on section10.1.6 of the MPC8270 Reference Manual) with the clock configure mode as: MODCK_H=0110, MODCK[1-3]=001 and PCI_MODCK=0.

 

I looked into mpc8280 errata on the PLL/DLL jitter but didn't found any thing that could cause the PLL/DLL clock is jittering/unstable jumping. I wonder if anyone using this device has seen the PLL behavior like this before? Please help.

 

Also, when I search for this problem, there is an errata "PNC14620" that talk about the PLL supply voltage filter problem. Could someone tell me how big of the noise on the PLL supply voltage (VCCSYNC1) that this errata referred to?

 

Thanks for your help

 

--Phuong

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