Renesas PCI Express clocks provide the “heartbeat” or reference clock for the integrated PCIe ports of FPGAs and embedded microprocessors. All these devices are available with integrated oscillators that use low-cost crystals at 14.318MHz or 25MHz as the input frequency. They can also accept a single-ended reference-clock input and convert it to a PCIe differential output with jitter specifications conforming to Generation 1 (86ps peak to peak) or Generation 2 (3.0/3.1ps RMS phase jitter) at the standard PCIe frequency of 100MHz. Some of the devices will also output other common PCIe frequencies that include 125MHz and 250MHz needed to drive widespread peripherals. Spread spectrum capability adds EMI reducing frequency modulation to the basic functionality of the clock synthesizers. By changing the clock frequency slightly in a pre-defined manner (triangular modulation), external interference is reduced below FCC legal limits, reducing the need for shielding or other remedial fixes.