LVDS

mylcx_xwf

【文件名】:06914@52RD_lvds_ch2.pdf
【格　式】:pdf
【大　小】:168K
【简　介】:2.1 Why low-swing differential?
The differential data transmission method used in LVDS is less susceptible to common-mode noise than
single-ended schemes. Differential transmission uses two wires with opposite current/voltage swings instead
of the one wire used in single-ended methods to convey data information. The advantage of the differential
approach is that if noise is coupled onto the two wires as common-mode (the noise appears on both lines
equally) and is thus rejected by the receivers, which looks at only the difference between the two signals.
The differential signals also tend to radiate less noise than single-ended signals due to the canceling of
magnetic fields. In addition, the current-mode driver is not prone to ringing and switching spikes, further
reducing noise.
Because differential technologies such as LVDS reduce concerns about noise, they can use lower signal voltage
swings. This advantage is crucial, because it is impossible to raise data rates and lower power consumption
without using low voltage swings. The low swing nature of the driver means data can be switched very
quickly. Since the driver is also current-mode, very low – almost flat – power consumption across frequency
is obtained. Switching spikes in the driver are very small, so that ICC does not increase exponentially as
switching frequency is increased. Also, the power consumed by the load (3.5 mA x 350 mV = 1.2 mW)
is very small in magnitude.
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