Center tap termination circuit and printed wiring board having center tap termination circuit

摘要

A center-tap termination circuit which includes two resistors having the same resistance, which are serially connected between forward and return transmission lines, where the forward and return transmission lines constitute a differential signal transmission line. A capacitor is connected between a connector that interconnects the two resistors and a GND of a printed circuit board. The forward and return transmission lines are substantially equidistant from each other along their lengths. The resistors and the capacitor are arranged outside the forward and return transmission lines. The connector is provided intersecting, in three-dimensional space, the forward and return transmission lines, such as being formed by a jumper bridging the two lines, or by being formed on a different layer of a multilayer printed circuit board. Variations in the differential impedance are suppressed, and the transmission return/transmission forward characteristics of differential signals are substantially matched. The differential impedance matching is achieved, and high-quality signal waveforms are maintained. Not only noise emitted due to differential mode current components, but also noise emitted due to common mode current components are suppressed.