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Optimizing impedance discontinuity caused by surface mount pads for high-speed channel designs

Posted: 24 Feb 2009 ?? ?Print Version ?Bookmark and Share

Keywords:application note? discontinuity impedance? design high-speed?

As data rates continue to increase, today's high-speed board designers face tremendous challenges upgrading their designs to meet increasing bandwidth requirements. When implementing high-speed designs, any small discontinuities in the physical geometries along the transmission path can significantly degrade the signal. This degradation includes loss of signal amplitude, reduction of signal rise time, and increased jitter. As a result, you must be able to identify these discontinuities in the high-speed channel and provide ways to mitigate their effects for better signal transmission.

Two commonly used components in a high-speed serial channel that can benefit from optimization are the DC blocking capacitors and SMA connectors. DC blocking capacitors are normally present in the channel to control the common mode voltage at the receiver while SMA connectors are widely used to allow you to interface the board to test instruments or other boards.

This application note examines the discontinuities from the DC blocking capacitors and SMA connectors in detail, and provides optimization techniques to minimize their adverse effects in the channel.

View the PDF document for more information.

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