[SI-LIST] EMI coupling of clock on other signals
- From: chundi srikanth <chundis@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 21 Jan 2010 23:52:16 +0530
Hi folks,
Iam working on a board which is of 16-layer and its a mixed signal board
which is having signals running at around 3GHz. Iam testing this board with
initial software. And we have one clock chip whose input is 30.72MHz and its
outputs are at 122.88MHz. And This board got an MCU whose highest running
frequency is 166MHz. And it was interfaced to a 32-bit SDRAM and it was
running on a clock speed of 83.33MHz. Today when i probed the 122.88MHz
clock out in a spectrum analyzer there is a strong spur of frequecy
components which were at 166.7, 215.8, 332.4MHz, 489.7MHz etc..... These are
almost harmonics of SDRAM clock frequency. And everywhere even if i probed
the GND the components can be seen. So what might be the problem and can you
suggest what can be done on board to resolve this.
Thanks in advance for your help.
Regards
Sree
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