Why we need to use a differential pair为什么我们使用差分线

What is a differential pair

In its most basic form, a differential pair is two transmission lines that have equal and opposite polarity signals traveling on them. The property that these two signals have in common is that they are equal and opposite and they are tightly timed to each other. Beyond these two characteristics there are no other properties that matter when a design uses differential pairs. Maintaining the equal and opposite amplitude and timing relationship is the guiding concept when using differential pairs.

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Why use differential pairs?


There are three reasons to use differential pairs in a digital or analog signal path. The most important one is that the ground
connection between the two ends of the signal path can be very poor and data quality will not be compromised.

 

A second reason to use differential signaling is that the link can suffer substantial attenuation of the signal and still function properly.

 

A third reason to use differential pairs is for data paths with very high data rates such as gigabit and higher links. It is possible to drive differential paths at rates as high as 10 Gb/S over copper traces in standard PCB materials. This is impossible to do with single-ended logic paths.

 

什么是差分对?

在其最基本的形式中,一个差分对是双传输线,在传输过程中具有相等的和相反的极性信号。这2个信号的共同点是,它们是相等的,相反的,它们是彼此紧连的。除了这2个特性,当设计使用差分对没有其他的特性了。使用差分对时保持相等和相对的振幅和正时关系的指导思想。

 

为什么使用差分对?

 

在数字或模拟信号路径中使用差分对的原因有三个。最重要的一个就是地面信号路径两端的连接可能很差,数据质量也会受到损害。

 

使用差分信号的另一个原因是,该连接可以承受相当大的信号衰减,并且仍然能正确地运行。

 

第三个原因是使用差分对数据路径具有非常高的数据速率,如千兆和更高的信号。在标准的印刷电路板材料中,它可以驱动高达10G/S的速度来驱动差分路径。对于单端逻辑走线这是不可能的。