[SI-LIST] Re: HDMI Frequency Failing RE Test by 7dB!!!!
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: ah.vinod@xxxxxxxxx
- Date: Wed, 23 May 2012 23:57:11 -0400
Hi Vinod,
Have you checked for serial clock leakage on the IO pins? Some chips
can be really bad
in that regard and can cause a lot of common-mode radiation issues even
with
otherwise good signal skew and symmetry.
Regards,
Istvan Novak
Oracle
On 5/23/2012 11:03 AM, vinod ah wrote:
> Hi,
>
> We have used common mode choke on the board. The serial data is at
> 742.5 Mbits/sec, but not 742.5MHz right? Also since TMDS signalling is
> used for HDMI signals, will the data on the HDMI cable be toggling at
> 742.5MHz? Please correct me if anything is wrong in my understanding.
>
> Regards
> VI\inod A H
>
> On Wed, May 23, 2012 at 8:29 PM, Rohit MISHRA<rohit.mishra@xxxxxx> wrote:
>> Hello Vinod,
>>
>> In HDMI 1080p pixel clock runs at 74.25 MHz but serial data rate is 742.5
>> MHz, right ?
>>
>> I would like to know if you have used common mode choke coil in your PCB and
>> if your answer is Yes then I believe culprit is your HDMI cable.
>>
>> Have you checked the Quality of Cable ?
>>
>> Best Rgds,
>> Rohit Mishra
>>
>>
>>
>>
>>
>>
>> -----Original Message-----
>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
>> Behalf Of vinod ah
>> Sent: Wednesday, May 23, 2012 7:28 PM
>> To: SI-LIST
>> Subject: [SI-LIST] HDMI Frequency Failing RE Test by 7dB!!!!
>>
>> Hi All,
>>
>> I am designing a board with HDMI input and HDMI output. I am facing
>> EMI issue at 742.5MHz (failing FCC limits by 7dB) when running 1080p30
>> on both Input and output HDMI i.e. BLu ray player connected to HDMI
>> input connector of my board is giving out data at 1080p30 and HDMI out
>> of my board is connected to TV which is also 1080p30 content. So i am
>> unable to find out how is 742.5MHz coming out as radiation as it is
>> 10th Harmonic of pixel clock 74.25MHz!!!!!!!. I am not facing any
>> issues with other harmonics except for this. So i am totally confused
>> on how to go about debugging this issue.
>>
>> Note: All the signals are routed on top layer without vias and all
>> signals have solid ground plane reference. The blu ray player and TV
>> used, is tested for radiation and no significant levels seen.
>>
>> Regards
>> Vinod A H
>>
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