今天小编要和大家分享的是布线技巧与EMC相关信息，接下来我将从ESD中的电容问题，max512esd这几个方面来介绍。
布线技巧与EMC相关技术文章ESD中的电容问题
ESD中的电容问题
如果电子模块有不用的引脚，那么我们如何去处理呢？我们在处理时，可以考虑直接连接到地平面上去。（参考福特公司的处理方案ELCOMP17）（Modules that have spare pins (never used in any version using the same PCB); these pins shall be tied to the module ground plane.）如果有射频接受模块的话，这些引脚的接地可能会造成射频接受性能的降低，这时候就不能使用接地的方式了，必须使用ESD的电容和放电电阻来消除静电的影响了。还有一种例外也是很常见的，如果这些不用的引脚附近有电源或者HSD输出的时候，我们就必须考虑把这些引脚接电容或者地了。显而易见的是，如果这些引脚相邻小于5mm，在不断的插拔过程中，引脚可能弯曲，这样会引起严重的断路事故，这是不被允许的。当然ESD电容和放电电阻不一定必须接到地，也可以接到阻抗低的电源。以上所有的措施都是为了防止静电从意想不到的路径传递到板上。我们看看ISO10605的描述
我们在设计ESD电容的时候，电容的容值是有限的，额定电压也是有限地，该如何去选取呢？总结如下：Applied Voltage Levels
- For a specific ESD test Level, the lower the value of capacitance under test, the greater the voltage applied.
- Higher values of capacitance can withstand high levels of ESD pulses。
- The actual applied voltage is also limited by air discharge, which is a function of the case size.
- Capacitor Capabilites
- C0G will wishstand higher levels of ESD for the same voltage rating and capacitance value
- Higher voltage ratings are important if higher ESD levels were going to be involved
- For the same chip size, as the voltage rating increases, the maximum capacitance available decreases
- Chip size has little effect on basic ESD capability,providing the same capacitance value is available at the same voltage rating
- For smaller chip sizes, the maximumu availabe capacitance at the same voltage rating decreases
- Reduction of chip size should be evaluated carefully for ESD critical appliactions.This is especially true if it is necessary to trade off voltage rating or capacitance value
- Use of 0603 chip sizes will most likely result in lower ESD levels.Air Breakdown is a factor to be considered
- Chip sizes samller than 0603 should not be used in ESD critical Applications
- C0G dielectric materials are close to ideal, and are not affected by voltage coefficients
- X7R dielectric materials are Ferro electric, this effect increase the voltage applied
- Higher voltage ratings are again desirable to reduce the impact of the voltage coefficient on the voltage applied
- Smaller size chips may also influence the impact of the voltage coefficient
关于布线技巧与EMC就介绍完了，您有什么想法可以联系小编。