Printed Circuit Board Interconnection System refers to the entire electrical path from the transmitter to the receiver on the PCB board, including chip package, connector, transmission line, via, connector, etc. The signal integrity problems caused by the interconnection effect are:
1, The delay signal is transmitted at a limited speed on the printed circuit board pattern track, and it takes a certain time for the signal to propagate from the transmitting end to the receiving end, which is the transmission line delay. When the transmission line is too long, the signal delay will affect the system timing. In high-speed digital systems, the delay of the transmission line depends on the dielectric constant of the dielectric material, the length of the transmission line, and the geometry of the cross section of the transmission line.
2, When the characteristic impedance of the Printed Circuit Board Interconnection System does not match the termination impedance of the source or the load, the signal will be reflected back along the transmission line at the transmitting end and the receiving end, causing distortion of the waveform and even overshoot and undershoot. Multiple reflections of the signal back and forth will produce ringing. The geometry of the wiring, incorrect line termination, discontinuity of the power plane, etc. will cause reflections.
3, The problem caused by the discontinuity of the interconnect is essentially a reflection. The discontinuity of the interconnect is the discontinuity of the impedance. When the signal is transmitted to it, it will cause reflection. In actual PCB board layout, discontinuities such as vias, cross-segments, corners, etc. are often encountered in Printed Circuit Board Interconnection.
4, Crosstalk is caused by the electromagnetic coupling between the wires. The mutual capacitance causes the current to be combined, and the mutual inductance causes the coincidence voltage. The traces in modern circuits are very dense, so the clutter between the trace itself and the electromagnetic field generated by the traces around it is very serious. When the crosstalk voltage is large enough, it may cause serious functional problems of the circuit. On Printed Circuit Board Interconnection System, crosstalk is related to the length of the trace, the spacing of the lines, the direction of the transmitted signal in the line, and the termination mode and the condition of the reference ground plane.
