在线座谈

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关于本次座谈

座谈简介

自從1870年電話面世以來,通訊技術的發展可說一日千里,以前的線路只可傳送話音,但現在已發展至可以傳送包括視訊在內的各種資料。過去10年來,資料傳輸速度有大幅的提升。例如,若利用HDMI電纜傳送高解析度的視訊,頻寬便必須高達3.4Gbps,是56k數據機頻寬的6萬倍以上。由於資料傳輸速度有大幅的提升,因此我們不能再採用TTL等單端訊號,必須改用LVDS、CML及LVPECL等高速差動訊號。

美國國家半導體將會在今次的線上研討會討論“為何高速資料通訊必須採用差動訊號"和會探討利用個人電腦電路板或電纜傳送差動訊號的問題。並以DVI/HDMI電纜延長解決方案作為實例,讓各位明白如何利用訊號調節晶片解決有關問題。最後,美國國家半導體會為各位介紹多個適用於高速訊號傳輸系統的PCB設計方案,並詳細解釋其中採用的技術。

精彩问答

主题:高速訊號路徑的設計問題 -- DVI/HDMI 電纜延長方案的挑戰
在线问答:
[主持人:ChinaECNet] 各位聽眾(網友),上午好!歡迎參加中電網線上座談。今天,我們有幸邀請到美國國家半導體公司的專家就“高速訊號路徑的設計問題 -- DVI/HDMI 電纜延長方案的挑戰”舉行線上座談。在座談中,您可就您關心的問題與美國國家半導體公司的專家線上進行直接、即時的對話交流。中電網衷心希望通過大家的共同努力,不僅能夠增進各位聽眾(網友)對“高速訊號路徑的設計問題 -- DVI/HDMI 電纜延長方案的挑戰”的瞭解和掌握,而且能夠為大家事業的發展帶來裨益。  [2007-7-25 10:23:53]
[问:jjhwl] DVI/HDMI 電纜延長最远是多少? 
[答:Robertshen] Depend on the type of cable. If you use Cat5 cable, 20M is limited.  [2007-7-25 10:46:06]
[问:jjhwl] DVI/HDMI 電纜延長方案对电缆有什么特殊要求?  
[答:DavidYang] Currently, National products support three type of cables for HDMI/DVI like HDMI, DVI and CAT5 cable. If you want to extend more length, you can also do a connection with optical module to support fiber cable. Another thing need to meet HDMI/DVI spec like jitter, rising and falling time requirement and so on  [2007-7-25 10:46:12]
[问:alexzheng] 針對不同的信號速率,我們一般都用什麼方式對LVDS信號進行分發處理? 
[答:StanleyTseng] If the signals are LVDS, even it"s different speed ( while still within LVDS specification for length & speed), the way we could use is LVDS serializer, deserializer, or LVDS buffer.  [2007-7-25 10:47:58]
[问:lralra] LVDS信號在PCB佈線“過孔”時,有哪些問題需要注意? 
[答:Noelfung] Vias will creat parasitic capacitance, stub and reflection. For multi-layer pcb, we suggest use blind vias to reduce the effect of the via  [2007-7-25 10:48:10]
[问:alexzheng] 能推荐用什么样的仪表进行生产测试呢? 
[答:JanetWu] You have to contact HDMI certified lab to perform the test. Or you can do a pre-test with some specific scope that is capable of performing the test.  [2007-7-25 10:50:02]
[问:RuibinHsia] 當有多個HDMI輸入的時候,肯定要經一個多工器,這時應該注意一些什麼呢? 
[答:DavidYang] 1. DDC 2. Impendance control 3. Put device close to connector as possible   [2007-7-25 10:50:54]
[问:gaochunzy] 请问NS在南京有没有什么办事处等 
[答:Alicehui] We don"t have office in Nanjing. If you want to get information about our products, please contact our distributors http://www.national.com./CHS/contacts/Details/0,1596,China_bycity,00.html#Nanjing)in Nanjing.  [2007-7-25 10:50:58]
[问:alexzheng] DVI/HDMI 電纜延長方案对电缆有什么特殊要求? 
[答:DavidYang] 1. To meet HDMI spec like Jitter, rising time, falling time, ampltude etc 2. To reduce crosstalk effect as possible   [2007-7-25 10:53:41]
[问:HsuehChinLin] 針對不同的信號速率,我們一般都用什麼方式對LVDS信號進行分發處理? 
[答:Andrewchiu] If the signals are LVDS, even it"s different speed ( while still within LVDS specification for length & speed), the way we could use is LVDS serializer, deserializer, or LVDS buffer.  [2007-7-25 10:54:05]
[问:TanQC] 請問HDCP是怎樣影響視頻信號的? 
[答:Noelfung] It will not affect the video signal directly. In fact, it will tell the driver (e.g. HD DVD player) or the receiver (e.g. display) whether the video content is licensed or not and adjust the output resolution accordingly.  [2007-7-25 10:55:25]
[问:jida_song] LVDS差分線在電路排板時應有哪些注意事項? 
[答:Noelfung] 1. same length 2. place differential pair as close as possible, "s" 3. place adjcant differential pair at least 2"s" away 4. place TTL signal at least 3"s" away 5. reduce the use of via  [2007-7-25 10:57:29]
[问:孫槿] LVDS與RS422/RS485 的應用設計比較有哪些優點? 
[答:Robertshen] lower EMI, lower power, higher speed, lower cost.  [2007-7-25 10:58:46]
[问:sorryhaha] LVDS系統設計時,LVDS接收器的未使用的空閒管腳一般如何處理? 
[答:Noelfung] Normally, they can be left open. However, you can add some resistors to "bias" the receiver input such that the TTL output is a known stage. We call this "failsafe". Pls refer to National"s application note AN-847 for details  [2007-7-25 10:59:38]
[问:nuaawqy] HDMI要求支援熱插拔是不是要求在HDMI信號線插上之後能夠自動檢測到HDMI信號顯示?如果當前狀態不是在HDMI的時候是否也要求轉換到HDMI狀態? 
[答:DavidYang] 1, It is not necessary for signal detection because this is impage transmission that allow to lost some a little bit. 2. HDMI and DVI are same singal format so no any need to do any conversion except connector  [2007-7-25 11:00:07]
[问:aya1230] 有的設計中在差分數據通路上加共模抑制器,是否有必要? 
[答:Alicehui] 共模抑制器能更好的抑制共模干擾,根據系統要求確定。  [2007-7-25 11:00:36]
[问:feihuo01] HDMI 提供安全介面嗎? 
[答:StanleyTseng] Yes, there"s the secuity rule defined in HDMI to prevent content copy -- above all video content.  [2007-7-25 11:00:48]
[主持人:ChinaECNet] 我們已經進入問答階段如果聽眾想重溫演講或內容可以點擊下面“回顧演示”重看演講。  [2007-7-25 11:03:33]
[主持人:ChinaECNet] 各位觀眾,現在用戶提問很踴躍,專家正在逐一回答。請耐心等待您問題的答案,同一問題請不要多次提交。  [2007-7-25 11:03:46]
[问:wangsea] 请问在高速信号传输过程中,抖动的产生机理有哪些? 
[答:Robertshen] The major reason is noise added to phase. And system clock has jitter also.  [2007-7-25 11:04:42]
[问:孫槿] LVDS系統在雜訊環境中如何提高設計的可靠性? 
[答:DavidYang] 1. Read layout guide that National provide 2. Or go to National website to get LVDS owner Manual 3. The distance in between LVDS and LVDS, it need 2S at least, that specified in LVDS owner manual 4. The distance in between LVDS and TTL/CMOS, it need 3S at least, that specified in LVDS owner manual. 5. Impedance to meet 50 Ohm for single-end and 100 Ohm for differential 6. To reduce crosstalk, you may use shielding cable   [2007-7-25 11:05:27]
[问:劉聚成] 清介紹一下DS38EP100無源等化器的工作原理. 
[答:Noelfung] actually, an EQ is a high pass filter. Backplane and cables are bandwidth limited and act as low pass filters, effectively filtering out high frequency components of a signal. The EQ counteracts or "flatten" the backplane"s frequency response  [2007-7-25 11:05:32]
[问:Alice Hui] Will the passive equalizer provide any ESD protection? 
[答:Andrewchiu] The architecture of the passive equalizer does not provide any ESD improvement, it is simply passed through the signal.  [2007-7-25 11:06:25]
[问:jwyansz] TMDS信號線如果對EMI產生影響我們用什么方法來解決對TMDS信號影響最小 
[答:JanetWu] Balanced cables (twisted pair) are usually better than unbalanced cables (ribbon cable, multi-conductor) for noise reduction and signal quality. Balanced cables tend to generate less EMI due to field canceling effects. They also tend to pick up electromagnetic radiation as common-mode (not differential-mode) noise, which is rejected by the receiver.  [2007-7-25 11:09:25]
[问:wujack53] 針對LVDS及TMDS的傳輸線和連接器 應如何選用 關鍵又是什麼 
[答:Noelfung] Generally speaking, Cables: low loss, low skew, low crosstalk, high return loss, preferably independently shielded Connectors: low crosstalk, high return loss  [2007-7-25 11:09:49]
[问:satellitehan] HDMI中的CEC主要是什麼作用啊? 
[答:Andrewchiu] Consumer Electornics Control (CEC) is used to command and control multiple CEC-enabled devices. For example, when you close the drawer of a DVD player, the player can command TV and any other AV products (all with CEC) to power-up, select the correct HDMI ports, etc.  [2007-7-25 11:09:51]
[问:aya1230] 您好,記數性均衡是不是脈衝整形,相當門電路銳化波形邊緣?在系統存在一定歪斜時這種均衡能否適用?謝謝! 
[答:DavidYang] 我不是很清楚你的問題,可以用英文從寫上的問題嗎?   [2007-7-25 11:10:54]
[问:TanQC] HDMI成品的絕緣測試要求應該是多少? 
[答:Noelfung] I think this is related to HDMI connector, I am sorry we are not familiar with this spec.  [2007-7-25 11:11:16]
[主持人:ChinaECNet] 各位觀眾,現在用戶提問很踴躍,專家正在逐一回答。請耐心等待您問題的答案,同一問題請不要多次提交。  [2007-7-25 11:14:43]
[问:wujack53] TMDS及LVDS訊號 在經常性插拔連接器的情況下 電路板設計如何因應 避免ic損壞 
[答:Noelfung] This is related to the ESD immunity of the devices. For example, HDMI has 8KV ESD requirement, if the EQ is not able to accept this level, you"ll have to add some external ESD protection devices.  [2007-7-25 11:15:02]
[问:lyn3210] 請專家詳細介紹HDMI介面標準及NS的實現方法.謝謝! 
[答:Robertshen] Please take HDMI standard as reference.  [2007-7-25 11:15:08]
[问:Johnny Wei] 我們用DS16EV5110當接收時,把EQ調到6,可以清楚顯示畫面,但是當EQ調到3或4時,畫片會有雜訊,既然DVI是數位訊號,要嘛顯示,要嘛不顯示,為何會有顯示但有雜訊現象? 
[答:DavidYang] 這表示 Cable lost 太多造成,而你又補償不足,所以訊號到接收端無法被辨識是 0 或 1  [2007-7-25 11:15:25]
[问:Betty Lee] 在可靠性要求高的場合,是否需要對接口進行相關的保護,如何對接口進行保護? 
[答:Alicehui] 是, 因為介面是最外的器件, 直接跟電纜相連. 可以選擇具有更高ESD保護等級的器件, 以及外加獨立保護器件.  [2007-7-25 11:17:02]
[问:LZHFHQ1024] HDMI規範中有一種可選的規範是CEC(消費電子控制),可以實現一些音視頻設備間的高級控制功能,比如支援視頻源和數位電視間的雙向通信,實現單鍵按下同時開機等功能。請教專家,這些功能是否大多數HDMI介面都支援?廠商可否利用這些規範開發一些差異化產品? 
[答:Noelfung] It is a marketing question rather than a technical question. As you"ve pointed out, HDMI has already reserved this feature. Deploy it or not is really up to the manufacturers.  [2007-7-25 11:18:40]
[问:劉聚成] LVDS 系統的設計中媒質(電纜和連接器)選擇原則? 
[答:Robertshen] cost, and signal quality  [2007-7-25 11:19:08]
[问:hunterzw] HDMI支持哪些方式的视频编码? 
[答:DavidYang] 8, 10, 12, 16 bit and up to 1080p  [2007-7-25 11:20:05]
[问:lyn3210] HDMI和DVI是什麼關係?是否可以相容? 
[答:Noelfung] The electrical property is the same. One major difference is DVI cannot support audio. In addition, some DVI still support analog video while that HDMI is fully digital. Since the electrical property is the same, there is a DVI-to-HDMI adopter available in the market.  [2007-7-25 11:21:24]
[问:npu_xubin] 这种电缆主要应用于什么领域?在通信领域里用在哪些行业呢? 
[答:Noelfung] Which cable were you referring to?  [2007-7-25 11:22:53]
[问:jida_song] 請問HDMI介面和SPDIF介面有什麼聯繫和區別?SPDIF介面目前在主流高清電視設計方案中是必備的音頻輸出介面嗎? 
[答:StanleyTseng] In consumer product, HDMI transfer both video & audio "digital" information. e.g. You can connect HDMI cable between DVD player to TV ( many newer TV, DVD Player already support HDMI ). SPDIF is only pure digital audio data. Mostly DVD player provide SPDIF so that you can connect to good audio amplifier.  [2007-7-25 11:23:06]
[问:hunterzw] LVDS有哪些基本参数? 
[答:Robertshen] Vod, Vos, Isa, Isb, Tr, Tf,Iin, Vth, Vin  [2007-7-25 11:23:26]
[问:FelixLCC] 請專家解釋什麽是TMDS(Transition Minimized Differential Signaling)通道?它有什麽優點? 
[答:DavidYang] TMDS,這是一種與 CML 大致相同的高速訊號 800mV amplitude 可以支援高達10Gps 頻寬 Long cable support  [2007-7-25 11:24:12]
[问:RuibinHsia] 一般在HDMI輸入後都經過一個電感器件是不是為了保證電路電流穩定呢?加電阻器是不是進行電壓匹配嗎? 
[答:JanetWu] Yes you"re correct.  [2007-7-25 11:24:12]
[问:hunterzw] 标准 HDMI 电缆能否在高速情况使用? 
[答:Robertshen] Depend on the speed. Generally, it can be used.  [2007-7-25 11:25:44]
[问:omap1710] 能不能簡單介紹一下CDR方法的優缺點?非常感謝! 
[答:Noelfung] CDR can clean clock and data. Therefore, if a device has CDR, you can expect the output is either a clean (low jitter) data or clock or both.  [2007-7-25 11:25:55]
[问:npu_xubin] 电缆的特征阻抗是多少? 
[答:DavidYang] 75 Ohm for 同軸電覽線 50 Ohm for single-end of ethernet cable  [2007-7-25 11:26:45]
[问:william_hsu] 據說HDMI介面的延長距離,通過內置有影像整理電路(將HDMI輸入信號以數碼方式重新整理排序、然後再以加壓數碼方式輸出HDMI信號),能把1080p的信號傳輸至50米遠.請問NS的方案是否具有影像整理電路?它是如何延長的? 
[答:Noelfung] No, we don"t. We focus on the "signal integrity" rather than signal processing. In addition, the compression method you mentioned will degrade the video quality.  [2007-7-25 11:29:13]
[问:zl184103] 和IEEE 1394相比,HDMI有何優勢? 
[答:Noelfung] 1394 has only 480M bandwidth, far behind HDMI. Remember that the bandwidth of each HDMI data channel is at least 1.65G  [2007-7-25 11:31:31]
[问:FelixLCC] 請介紹HDMI電纜延長,採用NS方案的優點和特點. 
[答:DavidYang] 介紹你一個功能非常強大的產品-DS16EV5110, 它的優點有: support HDMI V1.3 8KV ESD protection 支援 24 AWG 可 > 40 meter 支援 ethernet cable like CAT5E/CAT6/CAT7 支援DVI/HDMI cables   [2007-7-25 11:33:04]
[问:omap1710] NS有無TMDS發送器產品? 
[答:Andrewchiu] No, we don"t.  [2007-7-25 11:34:40]
[问:cai19761129] 無源等化器和有源等化器在電纜延長時那個會更好? 
[答:DavidYang] 當然是有源等化器啦!   [2007-7-25 11:35:31]
[主持人:ChinaECNet] 各位觀眾,現在用戶提問很踴躍,專家正在逐一回答。請耐心等待您問題的答案,同一問題請不要多次提交。  [2007-7-25 11:36:26]
[问:cai19761129] 將一路LVDS信號最多能發送到多少個接收器件呢? 
[答:StanleyTseng] Normally LVDS is one to one connection. While you can use LVDS repeater (e.g. DS90LV110ATMT) so that you can connect up to 10 receivers.  [2007-7-25 11:37:15]
[问:astrolzw] 請專家描述HDMI資料傳輸過程.爲什麽一根HDMI資料線可以同時傳輸視頻信號和音頻信號? 
[答:DavidYang] 因為一條 HDMI cable己 經把那些DDC/TMDS/Audio都整合進去啦!所以你只有看到好像一條Cable.  [2007-7-25 11:37:50]
[问:liyong98847] 能否简单介绍一下LVDS信号的抗噪特性? 
[答:Robertshen] As it is differentail, it is easy to resist commom mode noise.  [2007-7-25 11:38:12]
[问:wujack53] LVDS及TMDS 可使用的ESD保護等級的器件 有哪些可以舉例說明嗎? 
[答:Noelfung] One point need to clarify, National does not provide ESD protection devices. The fact is, we have a lot of LVDS devices that by default can withstand high ESD. For example, we have a lot of LVDS buffer devices that has ESD rating over 8kV.  [2007-7-25 11:39:09]
[问:astrolzw] HDMI有三個TMDS資料資訊通道,它們傳輸什麽樣的資料資訊? 
[答:DavidYang] 8, 10, 12, 16 bits transmission  [2007-7-25 11:39:32]
[问:liyong98847] 使用终端电阻实现对差分传输线的最大匹配时,在PCB布线时。对该电阻有什么需要注意的吗? 
[答:Robertshen] It is designed as near as possible to match 100 Ohm in design.  [2007-7-25 11:39:55]
[问:liyong98847] LVDS接收器在噪声环境中如何保证它的可靠性? 
[答:Robertshen] balance, and symmetry is important.  [2007-7-25 11:41:00]
[问:zhengyingjun] NS的EP100能否對HDMI傳輸線的外部干擾進行有效的抑制? 
[答:Noelfung] Probably not. It is being used to open up the eye. You have to pay attention to, say pcb layout or shielding.  [2007-7-25 11:42:49]
[问:jwyansz] 對於熱插把信號,機器和機器間是如何來識別的 
[答:StanleyTseng] For HDMI hot plug, it"s not necessary to have way to identify each other. Normally it"s single way -- one is transmitter, one is receiver. Not like USB or 1394 which provide bi-direction communciation so it would need some ID protocol.  [2007-7-25 11:42:49]
[问:jwyansz] 目前貼片的HDMI CONNECTOR在生產過程中一點都不好做,如果我改用插件DIP的會有什么影響嗎 
[答:Robertshen] It should increase inductance load.  [2007-7-25 11:43:03]
[问:scale_xie] LVDS 与 RS422/RS485 的应用设计比较有哪些优点? 
[答:Andrewchiu] LVDS has support lower EMI, lower power, and higher speed.  [2007-7-25 11:43:16]
[问:jem151] PCB佈線的時候要注意哪些問題? 
[答:JanetWu] Such as noise, vias, tracing...  [2007-7-25 11:47:05]
[问:zhengyingjun] NS的産品是否可用於HDMI信號光傳輸線? 
[答:Noelfung] That"s depend on how you are going to implement HDMI over optical. National has many signal conditioning devices that would certainly fit somewhere in the HDMI optical system  [2007-7-25 11:47:36]
[问:feihuo01] 問一下有沒有幾款預加重,去加重,均衡晶片?有domo broad沒有? 
[答:DavidYang] 可以知道你的應用嗎?  [2007-7-25 11:48:10]
[问:zl184103] 什麽時候需要HDMI介面? 
[答:JanetWu] Almost all kinds of digital video/audio signal such as 1080P/1080i/720P etc. It"s getting popular in both AV and PC market.  [2007-7-25 11:48:13]
[问:scale_xie] 在印制板上,两条差分线之间的距离是不是越短越好?为什么? 
[答:Robertshen] Yes, this helps to eliminate reflections and ensures that noise is coupled as common-mode. Signals that are 1 mm apart radiate far less noise than traces 3 mm apart, as magnetic field cancellation is much better with the closer traces. In addition, noise induced on the differential lines is much more likely to appear as common-mode which is rejected by the receiver.  [2007-7-25 11:48:18]
[问:BTVWF] 和直接输出HD-SDI相比,DVI有何優勢? 
[答:Noelfung] They are different. HD-SDI is regarding the raw "video data" while that DVI or HDMI is "color data".  [2007-7-25 11:49:57]
[问:zhouyang39] 請問專家,那裏可找到TMDS協定?它和DVI協定有和區別? 
[答:StanleyTseng] You can visit this site to get the information you need: http://www.hdmi.com/ There"s the relationship between TMDS & DVI. Basicly DVI & HDMI use TMDS signal protocol.  [2007-7-25 11:50:07]
[问:zhengyingjun] HDMI的傳輸距離一般爲15米,延長一倍到30米,價格上是否會翻倍? 
[答:DavidYang] 價格是一定會貴很多,但是你也可以選用像CAT5E 的產品降低你的成本  [2007-7-25 11:50:17]
[问:wujack53] TMDS及LVDS 電纜選用重點為何? 是否有建議使用的電纜 
[答:DavidYang] LVDS  - CAT5E cable that we suggest TMDS - HDMI/DVI cables, CAT5 (Need a driver or EQ to compensate it)  [2007-7-25 11:51:44]
[主持人:ChinaECNet] 所有問題均已提交給美國國家半導體公司的專家。座談期間未回答的問題,美國國家半導體公司專家也會逐一回答,並在中電網上公佈,請大家注意收看。  [2007-7-25 11:56:09]
[主持人:ChinaECNet] 由於時間關係,本次中電網“線上座談”馬上就要結束了。雖然各位聽眾(網友)已與美國國家半導體公司的專家討論了許多問題,但是還有許多提問沒有來得及進行交流。本次線上座談結束後,中電網將請美國國家半導體公司的專家繼續答復所有的來自各位聽眾(網友)的提問,然後整理上載到中電網網站上,以便大家查閱。  [2007-7-25 11:56:22]
[主持人:ChinaECNet] 在此,中電網特別感謝給予本次中電網線上座談巨大支持的美國國家半導體公司,特別感謝專門線上回答各位聽眾(網友)提問的美國國家半導體公司的各位專家們,特別感謝各位聽眾(網友)積極熱情的參與。   [2007-7-25 11:59:38]
[主持人:ChinaECNet] 祝大家事業有成、生活愉快!歡迎多提寶貴意見,歡迎關注中電網,下次再見  [2007-7-25 11:59:48]
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