The Si52143 is a spread-spectrum enabled PCIe clock generator that can source four PCIe clocks and a 25 MHz reference clock. The device has three hardware output enable pins for enabling the outputs （on the fly while powered on）， and one hardware pin to control spread spectrum on PCIe clock outputs. In addition to the hardware control pins， I2C programmability is also available to dynamically control skew， edge rate and amplitude on the true， compliment， or both differential signals on the PCIe clock outputs. This control feature enables optimal signal integrity as well as optimal EMI signature on the PCIe clock outputs. Refer to AN636 for signal integrity tuning and configurability. Measuring PCIe clock jitter is quick and easy with the Silicon Labs PCIe Clock Jitter Tool. Download it for free at www.silabs.com/pcie-learningcenter.