在线座谈

热门关键字: 双绞线 触摸技术 传感器原理 视频放大器 

关于本次座谈

座谈简介

自从1870年电话问世以来,通信技术的发展可说一日千里,以前的线路只可传送话音,但现在已发展至可以传送包括视频信号在内的各种数据。过去10年来,数据传输速度有大幅的提升。例如,若利用HDMI电缆传送高分辨度的视频信号,带宽便必须高达3.4Gbps,是56k调制解调器带宽的6万倍以上。由于数据传输速度有大幅的提升,因此我们不能再采用TTL等单端信号,必须改用LVDS、CML及LVPECL等高速差分信号。

美国国家半导体将会在今次的网上研讨会讨论“为何高速数据通信必须采用差分信号”和探讨利用个人电脑电路板或电缆传送差分信号的问题。并以DVI/HDMI电缆延长解决方案作为实例,让各位明白如何利用信号调节芯片解决有关问题。最后,美国国家半导体会为各位介绍多个适用于高速信号传输系统的PCB设计方案,并详细解释其中采用的技术。

精彩问答

主题:高速信号路径的设计问题 -- DVI/HDMI 电缆延长方案的挑战
在线问答:
[问:hkunming0668] 1.目前优质DVI/HDMI 电缆最长可达几米? 2.对电缆的量测有哪些量测项目? 3.对电缆的量测有哪些解决方案 
[答:Benwang] DVI/HDMI通过DVI/HDMI电缆传输的距离一般在5米以内.  [2007-7-24 10:43:39]
[主持人:ChinaECNet] 各位听众(网友),上午好!欢迎参加中电网在线座谈。今天,我们有幸邀请到美国国家半导体公司的专家就“高速信号路径的设计问题 -- DVI/HDMI 电缆延长方案的挑战”举行在线座谈。在座谈中,您可就您关心的问题与美国国家半导体公司的专家在线进行直接、实时的对话交流。中电网衷心希望通过大家的共同努力,不仅能够增进各位听众(网友)对“高速信号路径的设计问题 -- DVI/HDMI 电缆延长方案的挑战”的了解和掌握,而且能够为大家事业的发展带来裨益。  [2007-7-24 10:46:15]
[问:percy_wang@ali.com.tw] 如何控制PCB的布线阻抗?根据经验而言,需要考虑的重点有哪些? 
[答:Robertshen] 主要是线型,如微带线、夹心线等。具体可以参看有关文献计算。 [2007-7-24 10:46:23]
[问:Genius_XL] HDMI电缆这么大的带宽,我想问一下它的信号干扰问题是怎么解决的? 
[答:Noelfung] usually the core will be shielded to reduce crosstalk or interference  [2007-7-24 10:46:44]
[问:wangchen] 1 美国国家半导体关于DVI/HDMI领域最新发展的技术都有哪些?与其它公司相比有何优势? 2 关于DVI/HDMI领域最新发展的技术的主要应用? 
[答:Benwang] 国半在高速数据传输方面技术领先, 这些技术也可以应用于DVI/HDMI领域. 主要的优势包括: 高速(3.4Gbps HDMI V1.3), 可靠(8KV ESD), 低功耗, 小封装.  [2007-7-24 10:48:01]
[问:huatingxp] 请问能不能介绍一下,各种差分信号(LVDS、CML及LVPECL等)的电平标准,以及在实际应用中以上差分电平支持的最高传输速率为多少? 
[答:Stevenfeng] LVDS:350mV   3Gbps CML:800mV    10Gbps LVPECL:800mV  5Gbps  [2007-7-24 10:48:40]
[主持人:ChinaECNet] 我们已经进入问答阶段如果听众想重温演讲或内容可以点击下面“回顾演示”重看演讲。  [2007-7-24 10:48:45]
[问:wenjing62] HDMI几个规范有那些什么区别?是否向后兼容? 
[答:Benwang] 主要的区别是速率, HDMI v1.3支持 3.4Gbps 16-bit deep color. 支持向下兼容.  [2007-7-24 10:50:11]
[问:wenjing62] 和现有的模拟接口如复合、S-Video 和分量视频相比, HDMI的优点有哪些? 
[答:Robertshen] 没有可比性。HDMI是数字高清信号标准。  [2007-7-24 10:50:53]
[问:Thomas Li] 请教NS专家两个问题: 1.HDMI是否会被display port取代?或者是两者共存的局面? 2.HDMI电缆延长方案,目前NS有repeater的解决方案么? 
[答:Noelfung] 1. DisplayPort is still in the very preliminary stage while that HDMI is getting popular in both AV and PC market. I think, in the near future, HDMI will dominate the market. 2. As of today, we only have EQ.  [2007-7-24 10:51:01]
[问:peng_peng] 通常我们对DVI信号,是采用严格参考地平面来设计的。为了尽量减少其他信号对DVI信号的干扰,我们至少应该保持其他信号距离DVI信号多少距离才合适? 
[答:Noelfung] Remember that there is parameter called "s" in the pcb layout section? "s" is the separation between the differential pair. We usually place adjacent differential pair at least 2s away. Place TTL signals at least 3s away.  [2007-7-24 10:54:16]
[问:ys3663391] 针对不同的电缆,是不是也有不同的方案,还是在一定范围内方案都能适用 
[答:Benwang] 可以这样说, 例如, DS16EV5110 可以用在HDMI/DVI电缆和CAT5网线应用中.  [2007-7-24 10:54:27]
[问:cake_king] 如果两条线迹长度不同,有什么方法可以调整? 
[答:Robertshen] 如果是PCB布线的话,通过弯线来增加短线的长度,使之尽量相等。  [2007-7-24 10:55:33]
[问:zjlicool] 差分信号布线,两边需要加地线保护吗? 
[答:Benwang] 根据不同的应用可能不同, 具体可以参考国半"LVDS用户手册".  [2007-7-24 10:56:38]
[问:creative520] 各位专家好,我想问一下LVDS中的CDR问题,目前常用的CDR方法有那些?其优缺点有那些?对1G以上的LVDS信号其中的CDR关键问题是什么? 
[答:Noelfung] CDR is a difficult yet important issue in LVDS. There are several topologies to implement CDR, analog or digital. I don"t want to go over this topic in this seminar because it will take quite a long page to describe. Basically, the key element in CDR is the PLL.  [2007-7-24 10:57:37]
[主持人:ChinaECNet] 各位观众,现在用户提问很踊跃,专家正在逐一回答。请耐心等待您问题的答案,同一问题请不要多次提交。  [2007-7-24 10:59:01]
[问:zjlicool] 两层板如何控制差分阻抗? 
[答:Robertshen] 在一面平行布线,调整线的间距和线宽。  [2007-7-24 11:00:27]
[问:wyp791223] HDMI 支持哪种类型的视频? 
[答:Benwang] HDMI支持几乎所有的数字视频和数字音频. 例如: 1080P/1080i/720P 等等.  [2007-7-24 11:00:58]
[问:zhouyu0779] 如何減低供電線路所產生的噪音? 
[答:Stevenfeng] 选用较好DC/DC的转换器, 或好的低压降稳压器。例如:LM3674,LM1770,LM25576,LP38691.  [2007-7-24 11:01:06]
[问:yujie1104] 请问贵公司有没有有源的cable 延长方案?如何解决其供电的问题? 
[答:JanetWu] National Semiconductor has released a Video Equalizer for DVI, HDMI, and CAT5 Cables DS16EV5110 which can extend cable. Please go to our website for more information.  [2007-7-24 11:01:14]
[问:xl_cumt] PCB良好的设计如何做到好的S/N,如果采用双面板,能否做到好的抗干扰能力,再怎么说PCB板也只是在2维空间,对于三维空间的干扰,怎样处理? 
[答:Noelfung] We didn"t show the principle of microstrip line in the presentation. Basically, a transmission line on top of a "large" ground plane would confine the E-field of the transmission line within the dielectric of the pcb. As a result, the EMI or RF emission will be reduced. It would be easiler to understand if we could show you a picture, unfortunately, this on-line section doesn"t allow us to do so.  [2007-7-24 11:03:13]
[问:callancc] 用什么线传输LVDS信号(1G),和电路板的联接采用什么样的端口?需要注意些什么? 
[答:Benwang] 标准中没有规定LVDS的传输媒介, 可以是用CAT5, PCIe或专用线, 等等. 也没有规定具体的接口.  [2007-7-24 11:04:03]
[问:zjlicool] DVI/HDMI  电缆/插座认证机构有哪些? 
[答:Stevenfeng] ATC认证机构。  [2007-7-24 11:05:11]
[问:ys3663391] 在设计中如何平衡传输速度和损耗,有什么经验可以分享? 
[答:Noelfung] That depends on the transmission media. If the media is pcb, use low loss dielectric material and thicker copper cladding. If the media is cable, of course, you have to use high quality cable. For example, low loss, low crosstalk, low skew, shielded cable.  [2007-7-24 11:05:58]
[问:zhouyu0779] 在HDMI中如何加強信號路徑的性能? 
[答:Robertshen] 补偿方法,如加重/去加重、均衡等来提升信号的质量。  [2007-7-24 11:07:28]
[问:callancc] 800Mbps的串行信号,采用LVDS方式传输的话,比较保险的传输距离最长多远?是12米么? 
[答:Noelfung] This is a very typical question we got everyday. The answer is, that"s depend. For example, what type of cable you are using? In addition, if you have pre-emphasis or EQ, that will be another story. In addition, whether your data is DC-balanced or not will also affect the overall performance.  [2007-7-24 11:08:26]
[问:ylz8690@yahoo.com.cn] 电缆延长主要还是靠信号中继吗? 
[答:Robertshen] 中继是一个方法,也可以采用其它方法,如提高电缆的质量,提升信号的质量。  [2007-7-24 11:09:55]
[问:ylq661] 不同的电缆损耗不一样,预加重也不一样,在应用上如何进行预加重? 
[答:Benwang] 可以用带可调预加重的器件.  [2007-7-24 11:11:28]
[问:callancc] 我注意到一些芯片的管脚支持LVDS方式传输,并且输出电压2.5伏,请问这是业内的标准么?请问输出电压有更高些的么? 
[答:Noelfung] Usually, the common mode voltage of LVDS is 1.2V while that CML is 2.5V. LVDS is a standard while that CML is not. Since CML is not a standard, AC coupling is usually adopted  [2007-7-24 11:14:47]
[问:keenron] 阻抗断层的加重会不会加剧系统抖动,应如何减少这种回波带来的噪声影响呢?谢谢! 
[答:Benwang] 您指的是阻抗匹配问题吗? 阻抗不匹配是抖动的主要原因, 因尽量做到阻抗匹配.  [2007-7-24 11:15:47]
[问:hunterzw] 采用LVDS芯片,再加上预加重功能的支持,高频增益增幅能达到多少? 
[答:Noelfung] Typical gain is 3dB to 6dB  [2007-7-24 11:16:38]
[问:huamuzi12@etang.com] 交流耦合及互操作性问题该如何解决? 
[答:Benwang] 如果是不同的电平, 应使用AC偶合的方式.  [2007-7-24 11:16:53]
[问:yujie1104] 请问专家 DS38EP100的工作原理是什么?如何做到无源补偿? 
[答:Noelfung] Actually, an EQ is a high pass filter. So it doesn"t matter whether it is active or passive.  [2007-7-24 11:17:41]
[问:huijie] 无源均衡器和有源均衡器在使用上有什么优缺点? 
[答:Benwang] 有源EQ可以放大信号, 无源EQ对信号有衰减. 有源EQ需要耗电, 无源EQ不需要电源.   [2007-7-24 11:18:46]
[问:xiaobibi1984] 请专家解释,重复计时器是如何保证接收时钟和发送时钟同步? 
[答:Noelfung] There is a PLL inside a reclocker, so the PLL will lock to the incoming data and thus synchronized.  [2007-7-24 11:19:37]
[问:jimlee0924] 什么是UI?它代表多少时间? 
[答:Benwang] UI代表Unit Interval, 即单位比特的时间.  [2007-7-24 11:19:46]
[问:liyong98847] “标准”HDMI 电缆和“高速”电缆之间有何不同? 
[答:Robertshen] 主要是要符合HDMI的标准。见讲演资料的25页  [2007-7-24 11:20:28]
[问:zhouyu0779] National產品中是否有带可调预加重的器件? 
[答:Benwang] 有, 例如DS25BR100系列, 等等.  [2007-7-24 11:20:43]
[问:yujie1104] DS16EV5110可以用于不带独立电源的repeater设计吗?如何解决它的供电问题? 
[答:Benwang] 可以, 可以用电缆供电.  [2007-7-24 11:21:32]
[问:djwlwxl] 如何确定均衡器的补偿度?它和那些因素有关? 
[答:Noelfung] For adaptive EQ, the feedback system inside the EQ will determine the appropriate compensation. For settable EQ, the user can adjust the compensation by looking at the eye diagram coming out from the EQ or it could be determined by the system BER.  [2007-7-24 11:22:49]
[问:scale_xie] HDMI 相对于现有的模拟视频接口如复合、S-Video 和分量视频的优点有哪些? 
[答:Robertshen] HDMI是数字高清标准。与模拟视频信号没有可比性。  [2007-7-24 11:23:07]
[问:huatingxp] lvds信号传输,在做为输出,和输入时,有没有什么不同? 
[答:Benwang] 电平标准一样, 但匹配不同.  [2007-7-24 11:23:07]
[问:zhouyu0779] 如何解決電壓漂移時產生能量輻射,從而導致EMI的問題? 
[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.   [2007-7-24 11:23:45]
[问:zjlicool] 差分信号阻抗匹配电阻一般加在那一端比较好?(源端/负载端只允许加一个) 
[答:Benwang] LVDS信号在负载端加匹配.  [2007-7-24 11:24:19]
[主持人:ChinaECNet] 各位观众,现在用户提问很踊跃,专家正在逐一回答。请耐心等待您问题的答案,同一问题请不要多次提交。  [2007-7-24 11:24:48]
[问:szcharle] HDMI支持哪种类型的视频? 
[答:Andrewchiu] HDMI支持几乎所有的数字视频和数字音频. 例如: 1080P/1080i/720P 等等.  [2007-7-24 11:26:29]
[问:keenron] 关于走线.采用微带走线通孔相当串入电感,有好的办法改善其影响吗?是否可以通过电容匹配来补偿? 
[答:Robertshen] 首先尽量减少过孔。如果串入电感严重,可以通过增加电阻和电容网络来补偿。  [2007-7-24 11:27:06]
[问:peng_peng] 如何选择DVI的connector?除了要求它具有较低的损耗外,还应该考虑哪些因素。谢谢! 
[答:Benwang] 有标准的DVI接口, 选择满足标准的接口.  [2007-7-24 11:27:47]
[问:sorryhaha] 高速信号在传输时,怎么计算传输长度(带来电容、电感效应)对传输信号的影响? 
[答:Noelfung] That has to done by simulation. You got the simulation parameters from PCB vendor or cable manufacturer and then perform a simulation. This is the most accurate way to estimate.  [2007-7-24 11:27:56]
[问:liyong98847] HDMI 向后兼容 DVI (数字视频接口)吗? 
[答:Benwang] 是.  [2007-7-24 11:29:51]
[问:Alice Hui] Is it possible to use CAT5 cable in HDMI v1.3 application? 
[答:Andrewchiu] It is difficult but not impossible. CAT5 cable is cheap because it is not independently sealed, high skew, high loss and high cross talk. The problems get serious at high frequency. Even though you use a high quality CAT5 cable with excellent performance in the aforesaid parameters, you cannot overcome the cross talk appear in the RJ-45 connector.  [2007-7-24 11:31:52]
[问:amatist] 在可靠性要求高的场合,是否需要对接口进行相关的保护,如何对接口进行保护? 
[答:Benwang] 是, 因为接口是最外的器件, 直接跟电缆相连. 可以选择具有更高ESD保护等级的器件, 以及外加独立保护器件.  [2007-7-24 11:31:55]
[问:xiaobibi1984] LVDS和TMDS有什么区别? 
[答:Robertshen] TMDS是一类似CML信号。主要是电平的差别。  [2007-7-24 11:31:59]
[问:amatist] 有的设计中,在差分数据通道中加入共模抑制器,是否有必要? 
[答:Stevenfeng] 共模抑制器能更好的抑制共模干扰,根据系统要求确定。  [2007-7-24 11:32:20]
[问:peng_peng] 如何通过信号完整性的仿真,来评估一个具有DVI Connector和DVI电缆的通道。 
[答:Noelfung] I guess Spice model is the commonly used model today. If you have the spice model of the connector and cable, you can perform a simulation and see whether the eye diagram is good or not.  [2007-7-24 11:32:41]
[问:percy_wang@ali.com.tw] 高频增益是否会导致EMI问题? 
[答:Robertshen] 高频增益不会导致EMI。信号的幅度会导致EMI。  [2007-7-24 11:33:17]
[问:keenron] 由于累积电荷(长时间高电平或低电平)引起的符号间干扰应该如何均衡?自适应吗? 
[答:Noelfung] It would be difficult to compensate on the receiver side because some bits may have lost. You have to encode your TX data to DC-balanced type. For example, 8b/10b coding is one of the DC-balanced code.  [2007-7-24 11:35:09]
[问:chyren] 请问HDMI接口和SPDIF接口有什么区别? 
[答:Benwang] 不同的标准, HDMI包括视/音频, SPDIF是音频标准.  [2007-7-24 11:35:10]
[问:magic_2218] 请问HDMI信号的布线的宽度和长度的最佳方案是什么? 
[答:Robertshen] 要看PCB的材质而定。计算阻抗匹配为最佳。  [2007-7-24 11:37:21]
[问:yangao] HDMI 支持 Dolby Digital、DTS 和高分辨率的音频格式吗? 
[答:Noelfung] Yes, expecailly HDMI v1.3. It supports the latest digital audio technology.  [2007-7-24 11:37:37]
[问:move on] 高速信号路径的设计将如何避免一些干扰问题?? 
[答:Benwang] 遵守3S准则, 线对1S间距, 线对间2S, 差分与单端间3S.  [2007-7-24 11:39:59]
[问:yjbs] HDMI电缆延长线能够延长到几米的距离,能否由一个源分出多路来传输 
[答:Stevenfeng] 25米28AWG 1080P,20米CAT5 1080P. 点对点。  [2007-7-24 11:40:03]
[问:huamuzi12@etang.com] 我想问下HDMI接口的具体作用是传输纯数字信号(图象和音频)那 以后我们接数字电视信号需要这个接口吗,还是用别的什么接口来接收数字电视信号 
[答:Robertshen] 如果要接收或发送HDMI标准的视频信号,一定要用HDMI接口。  [2007-7-24 11:40:18]
[问:leeqianxang] 为什么忽略了寄生阻抗和阻抗不连续性的问题,则将在传输线上产生加性噪声,并出现误码? 
[答:Benwang] 这是由高速信号的特性决定的.  [2007-7-24 11:40:56]
[问:haoguil] HDMI是否可实现点对多点的传输?如果行,如何实现? 
[答:Stevenfeng] 不可以。  [2007-7-24 11:40:57]
[问:huatingxp] 差分信号和单端信号相比各有什么优缺点,在实际应用中怎么选择? 
[答:Robertshen] 请参见<LVDS Owner"s Manual - 3rd Edition>: http://www.national.com/appinfo/lvds/0,1798,100,00.html  [2007-7-24 11:42:29]
[问:w.liu] 无源均衡器只是一个高通滤波器,那么使用它会不会增加信号的毛刺和抖动? 
[答:Noelfung] If you compare the eye diagram before and after the EQ, you can tell the answer. You have a closed eye input and you get an open eye output. Since it is a passive device, you will not get over compensation even if the input signal is good. The only drawback is, the output amplitude will be a litte bit smaller than the input.  [2007-7-24 11:46:14]
[问:wenjing62] 在视频上使用HDMI, 有些什么好处和优势? 
[答:Robertshen] 用来传输高清数字电视信号。高速、方便,高性价比的方案。  [2007-7-24 11:46:16]
[问:scale_xie] 在设计系统是,采用支持预加重功能的LVDS芯片组驱动低成本的电缆,信号传送距离最多可达到多少? 
[答:Benwang] 这跟具体应用相关. 具体可参照DS25BR100系列DATASHEET.  [2007-7-24 11:46:53]
[问:zhouyu0779] National對ESD的保護問題有什麼好的解決方案? 
[答:JanetWu] We have different ESD protection for different product. Please go to our website and look at AN 1511 for your reference.  [2007-7-24 11:47:37]
[问:jimlee0924] HDMI传输的距离有多远,它和哪些的因素有关? 
[答:Robertshen] 与线的种类有关。如Cat5为20米。  [2007-7-24 11:48:34]
[问:liuxiaoli] HDMI 1.3的色深能达到多高? 这在效果上有什么变化? 
[答:Benwang] 16-bit deep color, 画面对比度更强烈.  [2007-7-24 11:49:07]
[问:skylion] 1.高速信号线有CRC错误怎么消除? 2.对于高速信号线的layout怎么优化? 
[答:Noelfung] 1. That has to done in the system level. For example, SDI signal in professional video application requires CRC in the signal processor. 2. The key of success is - balance. Same length, same width, same path, etc.  [2007-7-24 11:50:03]
[问:xl_cumt] 象视频高达3G多的带宽,是否还需滤波器,怎样的滤波器更好? 
[答:Benwang] HDMI传输中不需要.  [2007-7-24 11:51:19]
[问:chyren] HDMI 1.3 规范新增了哪些内容? 
[答:Benwang] 速度, 色深, 迷你型接口 等等  [2007-7-24 11:54:22]
[问:huatingxp] 当传输的信号的速率比较高的时候,由于PCB的布线的问题,怎么确保在信号的同步问题(如一路信号位宽为32,怎样确保数据的正确传输)? 
[答:Noelfung] Each trace must be same length. In addition, avoid as much bending as possible. Usually, the characteristic of PCB is rather even. So you would get quite a good balance if each trace is of the same length.  [2007-7-24 11:54:29]
[问:chyren] HDMI除了用在电视机上,还用在哪些地方? 
[答:Robertshen] 只要是有用到视频信号的地方,都会用到HDMI。  [2007-7-24 11:54:39]
[主持人:ChinaECNet] 所有问题均已提交给美国国家半导体公司的专家。座谈期间未回答的问题,美国国家半导体公司专家也会逐一回答,并在中电网上公布,请大家注意收看。  [2007-7-24 11:56:30]
[主持人:ChinaECNet] 由于时间关系,本次中电网“在线座谈”马上就要结束了。虽然各位听众(网友)已与美国国家半导体公司的专家讨论了许多问题,但是还有许多提问没有来得及进行交流。本次在线座谈结束后,中电网将请美国国家半导体公司的专家继续答复所有的来自各位听众(网友)的提问,然后整理上载到中电网网站上,以便大家查阅。  [2007-7-24 11:56:47]
[问:vince_zhang] 在发送接受端采取措施,并用Cat 1或2电缆传输,注意印制板布局走线的情形下,,LVDS,CML最长的传输距离能达到多少 
[答:Benwang] LVDS和CML只是信号电平标准, 跟距离没有直接的关系, 要传输更远的距离, 需要用到信号条理技术, 例如电缆驱动器/均衡器.  [2007-7-24 11:56:48]
[问:yangao] HDCP 是什么? 
[答:Robertshen] 是High bandwith Digital Content Protection。  [2007-7-24 11:57:51]
[问:leeqianxang] 提高信号传输质量的方法主要有哪些? 对电路连接器件有什么要求? 
[答:Benwang] 用更高等级的传输媒介,以及信号条理器件.  [2007-7-24 11:58:12]
[问:wangchen] How to reduce crosstalk? 
[答:Noelfung] Crosstalk usually appear between the core of the cable and the pins of the connector. If the core of the cable is independently shielded, you can reduce the crosstalk. Similar, a high quality or well design connector could reduce crosstalk too. That"s why we have DVI, HDMI, RJ45 connectors.  [2007-7-24 11:58:59]
[问:peng_peng] 请介绍一下CML、LVPECL高速差分信号及其主要应用,谢谢。 
[答:Stevenfeng] 应用于视频系统HD-SDI,DVI,HDMI1.3  [2007-7-24 11:59:00]
[问:daisy.liu@future.ca] 与MAXIM 等供应商的产品相比, 有哪些优势?  
[答:Andrewchiu] National"s Interface products features: - high-reliability, high speed data transmission - low power and low noise - high ESD/EMI protection - sharper images  [2007-7-24 11:59:27]
[主持人:ChinaECNet] 祝大家事业有成、生活愉快!欢迎多提宝贵意见,欢迎关注中电网,下次再见。  [2007-7-24 12:01:10]
[问:liuxiaoli] HDMI兼容测试,如何实现? 
[答:Noelfung] 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.  [2007-7-24 12:01:23]
[问:creative520] 对于1.2Gbps的LVDS信号,眼图的实际有效宽度大概是多大?如果对其进行过采样来进行CDR,几倍过采样比较合适?另外,几位lvds信号对齐后再和采样时钟对齐一般怎么解决?谢谢 
[答:Noelfung] One UI = 1/datarate. So the width of the eye is 1/1.2G. CDR is a complicated question that is not possible to go over here.  [2007-7-24 12:03:02]
非在线问答:
[问:leonqin] 请问NS有DisplayPort的相关产品吗?
[答:Noelfung] No, we don't  
[问:daisy.liu] 与MIXAM 等供应商的产品相比, 有哪些优势?
[答:Noelfung] National's Interface products features:  - high-reliability, high speed data transmission  - low power and low noise  - high ESD/EMI protection  - sharper images  
[问:wyp791223] 请专家详细介绍HDMI接口标准及NS的实现方法.谢谢!
[答:Noelfung] Pls refer to HDMI spec v1.3 for details, this spec is downloadable in the web. The key specifications have been discussed in today's seminar. National's DVI/HDMI EQ meet those requirement  
[问:huamuzi12] 我的显卡接口是15针VGA接口,但我又买了台只有DVI-D数字接口的液晶显示器,这样的两个接口能不能连,用什么样的线或转换器连接???
[答:Noelfung] I am afraid you cannot connect them together. VGA is analog while DVI-D accepts digital signal only.  
[问:huamuzi12] HDMI中的CEC主要是什么作用啊
[答:Noelfung] 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.  
[问:zhouyu0779] 如何加強信號路徑的性能?
[答:Noelfung] I think we should do it the other way. That is, reduce loss, skew, crosstalk, etc along the signal path.  
[问:amatist] 有的设计中在差分数据通路上加共模抑制器,是否有必要
[答:Noelfung] For LVDS, CML, LVPECL, these kind of differential signals do not require additional device to increase common mode rejection  
[问:xl_cumt] 信号调节芯片接口如何处理,怎样耦合才能保证不增加噪声?
[答:Noelfung] Coupling is a good topic that requires pages to explain. Remember how an eye diagarm is formed when we shown to you in the beginning of this seminar? If you have a long stream of 1's or 0's, AC coupling would create ISI and thus increase jitter. In short, AC coupling is suitable for DC-balanced data and non-compatible common mode voltage TX and RX. DC coupling is simple and good for LVDS.  
[问:huijie] NS有无TMDS发送器产品?
[答:Noelfung] No, we don't  
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