A designer has been designing their latest project. They created the hardware architecture, selected a microprocessor, FPGA, or more generally any chipset. All of the signals have been connected, all of the power lines laid out, everything is looking good. Then they stumble on a clock requirement spec from the chipset vendor. How should the designer supply a clock which meets these requirements? Many devices will content themselves of a plain, easy crystal. Others, however, have more complex clock requirements. Generally, chipset manufacturers provide the following specification for clocking: the frequency, the accuracy, the signal type (single-ended or differential) and its level (for instance, 2.5 V), the required jitter level (or sometimes a phase noise specification), as well as other parameters such as rise and fall times, etc. While specifications such as frequency, accuracy, signal types, etc. are easy to deal with, choosing clocks to match a certain jitter spec is more difficult.