[SI-LIST] 答复: Re: 答复: HDMI Frequency Failing RE Test by 7dB!!!!
- From: "Zhenwei Wang (zhenwwan)" <zhenwwan@xxxxxxxxx>
- To: <ehjchow@xxxxxxxxx>, <ah.vinod@xxxxxxxxx>, "SI-LIST" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 24 May 2012 13:56:19 +0800
Hi Jerry,
Thanks for your reminder. "Intra pair skew" will cause EMI issue not
"inter pair skew". My fault in typing.
BR
Zhenwei(Jason) Wang
Cisco Systems (Shanghai) Video Technology Co., Ltd.
-----邮件原件-----
发件人: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 代表
Jerry Chow
发送时间: 2012年5月24日 13:18
收件人: ah.vinod@xxxxxxxxx; SI-LIST
主题: [SI-LIST] Re: 答复: HDMI Frequency Failing RE Test by 7dB!!!!
HI Vinod :
I think it is actually the intra-pair skew that you want to check since it
is the one that will introduce Common mode noise. inter-pair skew is more of a
functional spec, not for EMI purpose.
Regards,
>________________________________
> From: vinod ah <ah.vinod@xxxxxxxxx>
>To: SI-LIST <si-list@xxxxxxxxxxxxx>
>Sent: Wednesday, May 23, 2012 8:03 PM
>Subject: [SI-LIST] Re: 答复: HDMI Frequency Failing RE Test by 7dB!!!!
>
>Hi All,
>
>I will try out experimenting with current probes for root causing the
>issue. Also I am going to EMI lab on Friday (India Time). Thanks for
>great suggestions. Will keep you all updated on the test results:-)
>
>Regards
>Vinod A H
>
>On Thu, May 24, 2012 at 7:34 AM, Zhenwei Wang (zhenwwan)
><zhenwwan@xxxxxxxxx> wrote:
>> Hi Vinod,
>> I went through the email about your issue. Yes, if the pixel clock is
>>74.25Mhz, the data rate is ten times of pixel clock, equal 742.5Mhz.
>>Conceptually, TMDS signal have a virtual AC ground. So there is no DC current
>>requirement through ground pin. My suggestion: you should check the parameter
>>"inter pair skew" of each differential data line.
>>
>> BR
>> Zhenwei(Jason) Wang
>> Cisco Systems (Shanghai) Video Technology Co., Ltd.
>>
>>
>> -----邮件原件-----
>> 发件人: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] 代表
>> vinod ah
>> 发送时间: 2012年5月23日 21:58
>> 收件人: SI-LIST
>> 主题: [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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