PCB设计问题集锦 问：PCB图中各种字符往往容易叠加在一起，或者相距很近，当板子布得很密时，情况更加严重。当我用Verify Design进行检查时，会产生错误，但这种错误可以忽略。往往这种错误很多，有几百个，将其他更重要的错误淹没了，如何使Verify Design会略掉这种错误，或者在众多的错误中快速找到重要的错误。 答：可以在颜色显示中将文字去掉,不显示后再检查;并记录错误数目。但一定要检查是否真正属于不需要的文字。 问： What’s mean of below warning:(6230,8330 L1) Latium Rule not checked: COMPONENT U26 component rule.答：这是有关制造方面的一个检查，您没有相关设定，所以可以不检查。 问： 怎样导出jop文件？答：应该是JOB文件吧？低版本的powerPCB与PADS使用JOB文件。现在只能输出ASC文件，方法如下STEP：FILE/EXPORT/选择一个asc名称/选择Select ALL/在Format下选择合适的版本/在Unit下选Current比较好/点击OK/完成然后在低版本的powerPCB与PADS产品中Import保存的ASC文件，再保存为JOB文件。 问： 怎样导入reu文件？答：在ECO与Design 工具盒中都可以进行，分别打开ECO与Design 工具盒，点击右边第2个图标就可以。 问： 为什么我在pad stacks中再设一个via:1(如附件）和默认的standardvi(如附件）在布线时V选择1，怎么布线时按add via不能添加进去这是怎么回事，因为有时要使用两种不同的过孔。答：PowerPCB中有多个VIA时需要在Design Rule下根据信号分别设置VIA的使用条件，如电源类只能用Standard VIA等等，这样操作时就比较方便。详细设置方法在PowerPCB软件通中有介绍。 问：为什么我把On-line DRC设置为prevent..移动元时就会弹出(图2),而你们教程中也是这样设置怎么不会呢?答：首先这不是错误,出现的原因是在数据中没有BOARD OUTLINE.您可以设置一个,但是不使用它作为CAM输出数据. 问：我用ctrl+c复制线时怎设置原点进行复制，ctrl+v粘帖时总是以最下面一点和最左边那一点为原点 答： 复制布线时与上面的MOVE MODE设置没有任何关系,需要在右键菜单中选择,这在PowerPCB软件通教程中有专门介绍. 问：用(图4)进行修改线时拉起时怎总是往左边拉起(图5)，不知有什么办法可以轻易想拉起左就左，右就右。答： 具体条件不明,请检查一下您的DESIGN GRID,是否太大了. 问： 好不容易拉起右边但是用(图6)修改线怎么改怎么下面都会有一条不能和在一起，而你教程里都会好好的(图8)答：这可能还是与您的GRID 设置有关,不过没有问题,您可以将不需要的那段线删除.最重要的是需要找到布线的感觉,每个软件都不相同,所以需要多练习。 问： 尊敬的老师:您好！这个图已经画好了，但我只对（如图1）一种的完全间距进行检查，怎么错误就那么多，不知怎么改进。请老师指点。这个图在附件中请老师帮看一下，如果还有什么问题请指出来，本人在改进。谢！！！！！答：请注意您的DRC SETUP窗口下的设置是错误的,现在选中的SAME NET是对相同NET进行检查,应该选择NET TO ALL.而不是SAME NET有关各项参数的含义请仔细阅读第5部教程. 问： U101元件已建好，但元件框的拐角处不知是否正确，请帮忙CHECK 答：元件框等可以通过修改编辑来完成。问： U102和U103元件没建完全，在自动建元件参数中有几个不明白：如：SOIC--》silk screen栏下spacing from pin与outdent from first pin对应U102和U103元件应写什么数值，还有这两个元件SILK怎么自动设置，以及SILK内有个圆圈怎么才能画得与该元件参数一致。 答：Spacing from pin指从PIN到SILK的Y方向的距离,outdent from first pin是第一PIN与SILK端点间的距离.请根据元件资料自己计算。
上传时间： 2013-10-07
上传用户：comer1123
This document provides practical, common guidelines for incorporating PCI Express interconnect layouts onto Printed Circuit Boards (PCB) ranging from 4-layer desktop baseboard designs to 10- layer or more server baseboard designs. Guidelines and constraints in this document are intended for use on both baseboard and add-in card PCB designs. This includes interconnects between PCI Express devices located on the same baseboard (chip-to-chip routing) and interconnects between a PCI Express device located “down” on the baseboard and a device located “up” on an add-in card attached through a connector. This document is intended to cover all major components of the physical interconnect including design guidelines for the PCB traces, vias and AC coupling capacitors, as well as add-in card edge-finger and connector considerations. The intent of the guidelines and examples is to help ensure that good high-speed signal design practices are used and that the timing/jitter and loss/attenuation budgets can also be met from end-to-end across the PCI Express interconnect. However, while general physical guidelines and suggestions are given, they may not necessarily guarantee adequate performance of the interconnect for all layouts and implementations. Therefore, designers should consider modeling and simulation of the interconnect in order to ensure compliance to all applicable specifications. The document is composed of two main sections. The first section provides an overview of general topology and interconnect guidelines. The second section concentrates on physical layout constraints where bulleted items at the beginning of a topic highlight important constraints, while the narrative that follows offers additional insight.
上传时间： 2013-10-15
上传用户：busterman
电源转换芯片
上传时间： 2013-11-14
上传用户：yeling1919
电源转换芯片
上传时间： 2013-11-01
上传用户：文993
Abstract: The rapid build out of today's smart grid raises a number of security questions. In this article,we review two recent well-documented security breaches and a report of a security gap. These situationsinclude a 2009 smart-meter hack in Puerto Rico; a 2012 password discovery in grid distributionequipment; and insecure storage of a private key in distribution automation equipment. For each of theseattacks, we examine the breach, the potential threat, and secure silicon methods that, as part of acomplete security strategy, can help thwart the attacks.
上传时间： 2013-10-27
上传用户：tecman
钲铭科电子SM2082是单通道LED 恒流驱动控制芯片， 芯片使用本司专利的恒流设定和控制技术，输出电流由外接 Rext 电阻设置为5mA~60mA，且输出电流不随环境温度和芯片 OUT 端口电压而变化。本芯片系统结构简单，外围元件极少，方案成本低。芯片间输出电流偏差<±4%，可与LED 共用PCB板，封装形式：TO252-2、SOT89-3
上传时间： 2013-10-28
上传用户：GHF
In this paper, two types of MMIC voltage controlled oscillators have been successfully demonstrated. The first chip with single tuning diode shows the excellent tuning linearity. The second chip with two tuning diodes can improve the tuning bandwidth.
上传时间： 2013-10-17
上传用户：xjz632
Many system designers need an easy way to producea negative 3.3V power supply. In systems that alreadyhave a transformer, one option is to swap out the existingtransformer with one that has an additional secondarywinding. The problem with this solution is that manysystems now use transformers that are standard, offthe-shelf components, and most designers want toavoid replacing a standard, qualifi ed transformer with acustom version. An easier alternative is to produce thelow negative voltage rail by stepping down an existingnegative rail. For example, if the system already employsan off-the-shelf transformer with two secondary windingsto produce ±12V, and a –3.3V rail is needed, a negativebuck converter can produce the –3.3V output from the–12V rail.
上传时间： 2013-10-09
上传用户：Jerry_Chow
Handheld electronic devices play a key role in our everydaylives. Because dependability is paramount, handhelds arecarefully engineered with lightweight power sources forreliable use under normal conditions. But no amount ofcareful engineering can prevent the mistreatment theywill undergo at the hands of humans. For example, whathappens when a factory worker drops a bar code scanner,causing the battery to pop out? Such events areelectronically unpredictable, and important data storedin volatile memory would be lost without some form ofsafety net—namely a short-term power holdup systemthat stores suffi cient energy to supply standby power untilthe battery can be replaced or the data can be stored inpermanent memory.
上传时间： 2013-11-05
上传用户：coeus
An essential component of a noise-free audio device isa clean power supply, but few switching regulators canoperate at high efficiency while keeping the switchingfrequency out of the audio band. The LTC®3620 fills thisvoid. It is a high efficiency 15mA buck regulator with aprogrammable minimum switching frequency, making itpossible to virtually eliminate audible switching noise. Theinternal synchronous switches and low quiescent currentof this buck regulator provide the ability to maintain highefficiency, while its small footprint makes it ideal for tiny,low power audio applications.
上传时间： 2013-10-21
上传用户：非衣2016
