求助USB 辐射超标

jiangweiamo

<p>我发一个图上来，是两种方案，供大家参考。</p><p>对于分地的那个 切记，在USB的PIN部分依然定义为GND。</p><p>USB的差分线上的相关保护我去掉了，我的图就仅仅是两种设计思想！</p>

jiangweiamo

两位牛人的英文不错。俺又要惭愧了。我就用中文说了一下。

cloud

引用第13楼sunny_su于2008-07-20 21:52发表的“”:

Hi cloud,
I don&#39;t know your experience. As I know, the vendor of chip will never provide the desing/layout to their user.  Except the degin guide. do you have any other suggestion?

Yes, the signal loop should be connected well.

Yes. You are right. If you are designing a critical circuit, cost sensitive and with big quantity, you should be able to check with chip supplier to get part of the layout in the chip. We have some experience with Freescale.

If you could not get it. Then, you will have to spend some time to search where to put the right filter. This, of course will be a time-consuming and boring job.

lht666666

看USB电路  IC输出的地方有串电阻吧

sunny_su

引用第16楼cloud于2008-07-23 05:49发表的“”:


Yes. You are right. If you are designing a critical circuit, cost sensitive and with big quantity, you should be able to check with chip supplier to get part of the layout in the chip. We have some experience with Freescale.

If you could not get it. Then, you will have to spend some time to search where to put the right filter. This, of course will be a time-consuming and boring job.

那你们一定是大客户，我没有问freescale要过layout，我相信我们是要不到的
出问题的也不是用freescale芯片的产品， 只有后者可以选择，昨晚测试到2点还是搞不定，命苦啊

sunny_su

引用第17楼lht666666于2008-07-25 09:04发表的“”:
看USB电路  IC输出的地方有串电阻吧

串电阻要看实际情况，如果你能保证自己的走线阻抗与芯片的输出阻抗匹配，可以拿掉的

b03050929

问下 加在 USB POWER and GROUND 上的bead  该用多大的？ &nbsp; 600ohm 1A的？

sunny_su

引用第21楼b03050929于2008-08-01 19:03发表的“”:
问下 加在 USB POWER and GROUND 上的bead  该用多大的？ &nbsp; 600ohm 1A的？

之前我用180ohm的Bead, 后来试过600ohm, RE有改善, 但是对其他部分有影响，最好还是能多测试几次，才能找到最合适的
个人认为选用多大的Bead和信号走线阻抗，割地处理，信号驱动的强度有一定的关系，只有试过才知道，没有万金油
[s:10] 拍砖

titan

可以尝试 将bead换成电容。0。01uf，0。1uf，

bovey

说了这样多，其实你们就忘记做一件事情，换台电脑
依我的经历，也是这个点，我换了电脑之后全部都好了