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lvds
LVDS offers the combination of low power and low EMI, important in applications such as laptop PCs, servers, routers, and switches. This differential signaling type provides up to 24 dB lower emissions than single-ended signaling and the 350-mV voltage swing is less than half that of LVPECL. The 350-mV swing is centered around a nominal voltage of 1.25 V. The LVDS driver consists of 3.5-mA nominal current sources connected to differential outputs via a switching network, sometimes referred to as an “H” switch. The outputs are typically connected to 100-Ω differential transmission lines terminated with a 100-Ω resistor across the receiver inputs. The resistor value matches the impedance of the transmission lines and provides a current path for the signal. The driver includes circuitry to set the common mode to 1.2 V nominally, regardless of VDD. Therefore, there is no need for externally biasing the driver to any specific voltage. Also, an LVDS output can be connected to any LVDS input without any concern about the actual supply voltage of the oscillator. Additional termination options and details can be found in the SiTime paper: Output Terminations for Differential Oscillators.
PTM Published on: 2018-01-31