[SI-LIST] Re: (EMI)spread spectrum clocking
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <kbagga31@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 5 Sep 2003 07:36:54 -0400
Karan,
The spread spectrum solution puts up to a few percent of frequency
modulation on the clock signal, with a low (10-100kHz) repetition frequency.
As long as the clock PLLs/DLLs in the system dont remove this modulation,
and assuming that the system timing allows for this modulation, it spreads
the energy of the clock over a wider spectrum and it becomes less disturbing
subjectively for instance to broadcast audio and video programs. The
measured peak interference also goes down, because legal compliance
measurements have to be taken with a pre-determined bandwidth: if you spread
the spectrum of the clock over a wider frequency band, the energy falling
into the measurement bandwidth will also be less.
Regards,
Istvan
----- Original Message -----
From: "karan bagga" <kbagga31@xxxxxxxxx>
To: <si-list@xxxxxxxxxxxxx>
Sent: Friday, September 05, 2003 6:09 AM
Subject: [SI-LIST] (EMI)spread spectrum clocking
> Hi Experts
>
> I want to know the fundamental physics behind spread spectrum clocking.
> How does modulating the clock frequency helps reducing EMI ?
>
> Thanks & Regards
> Karan
>
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