[SI-LIST] Re: Traces don't cause EMI - really?
- From: Ravinder.Ajmani@xxxxxxxx
- To: steve weir <weirsp@xxxxxxxxxx>
- Date: Mon, 2 Feb 2004 11:02:36 -0800
Steve,
Thank you very much for your help. I have located a single bus switch
from TI (SN74CB3T1G125), which should meet my requirement.
Regards, Ravinder
Server PCB Development
Hitachi Global Storage Technologies
Email: Ravinder.Ajmani@xxxxxxxx
steve weir <weirsp@xxxxxxxxxx>
02/02/2004 09:40 AM
To: Ravinder.Ajmani@xxxxxxxx, si-list@xxxxxxxxxxxxx
cc:
From: steve weir <weirsp@xxxxxxxxxx>
Subject: Re: [SI-LIST] Re: Traces don't cause EMI - really?
Ravinder,
Use a QuickSwitch type device at the ASIC. That is a pass switch only, so
the only penalty will be a parasitic RC for each pad.
Regards,
Steve.
At 09:26 AM 2/2/2004 -0800, Ravinder.Ajmani@xxxxxxxx wrote:
>Hi Folks,
>My problem relates to this topic, although I am looking for an entirely
>different solution.
>My board has pads for connecting an external fixture to obtain data
trace.
> The 8-bit data is transferred in sync with a 160 MHz clock, which is
>always active even if the trace port is not in use. The impedance
matched
>Microstrip clock trace is about 1.2" long, and unterminated trace acts as
>a nice antenna. With the help of close-field and far-field scans, I
have
>concluded that this my EMI problem is due to this clock. Also,
>terminating the clock at the pad has very little effect on emissions (Mr.
>Ritchey please note, traces do cause EMI). However, when I cut the clock
>trace near the ASIC, the emissions drop by about 10 dBs. It is too late
>for the redesign of ASIC to put a tri-state buffer, and I want to insert
a
>tri-state buffer at the clock output. The fastest single tri-state
buffer
>I have found (Toshiba TC7SZ125FU) has typical propagation delay of 2.5
ns.
> This delay will be too much for the synchronous data transfer.
>Can anyone suggest a faster single tri-state buffer for this application,
>or is there a better solution to this problem. I will appreciate your
>help.
>Regards, Ravinder
>Server PCB Development
>Hitachi Global Storage Technologies
>
>Email: Ravinder.Ajmani@xxxxxxxx
>
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