[SI-LIST] follow up: Re: Query about Oscillator problem
- From: "Li, Tianqi . (S&T-Student)" <tlx6f@xxxxxxx>
- To: "Li, Tianqi . (S&T-Student)" <tlx6f@xxxxxxx>, "chundi srikanth" <chundis@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sun, 31 Jan 2010 16:55:13 -0600
Sree,
I forget sth. You need to check the PLL filtering capacitors of MCF5212.
In most cases CPU will leave out 2 or 3 power pins for filtering PLL
noise. Capacitors on these pins should also use NPO for a better
performance.
And you also need to find at what value of Vpp of XTAL droped to the PLL
start to lose locking. If the value is out of MCF5212 spec, the root
cause is surely on XTAL tank circuit; If not, it might be XTAL's glitch
aroused. You can use scope to test the eye diagram and find the glitch.
Tianqi Li
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Li, Tianqi . (S&T-Student)
Sent: Sunday, January 31, 2010 4:44 PM
To: chundi srikanth; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Query about Oscillator problem
Hi Sree,
1) I think you should check the tuning capacitors temp. grade first. In
this case you need to use NPO grade. If you are using Y5V, it won't work
well when temp. changes a lot.
2) Make sure that the tuning capacitor's value is same as what
recommended in MCF5212 app. Notes.
3) If capacitors are OK, you need to check XTAL power consumption and
make sure that MCF5212 can drive the XTAL at low temp.
Tianqi Li
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of chundi srikanth
Sent: Saturday, January 30, 2010 10:18 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Query about Oscillator problem
Hi Friends,
I have designed a board with MCF5212 Processor and it was interfaced to
a
Pericom (saronix-ecera) NKS5 series quartz crystal. The crystals
operating
temperature was -40Deg c to 85Deg c. Earlier i tested this board and
everything was fine but now because the PLL was not locking and
processor
was working. So when i observed i noticed that at ambient temperature
the
crystal clock output was 2V p-p but with decrease in temperature the
clock
output was decreasing below 0.8V at -40 Deg c.
Can you just give me an idea about this problem and what might be the
problem in this scenario?
Thanks & Regards
Sree
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