7.3.12 Fine Adjustments for Phase Adjust and Phase SYNC

Phase SYNC refers to the process of getting the same phase relationship for every power-up cycle and each time assuming that a given programming procedure is followed. However, there are some adjustments that can be made to get the most accurate results. As for the consistency of the phase SYNC, the only source of variation could be if the VCO calibration chooses a different VCO core and capacitor, which can introduce a bimodal distribution with about 10 ps of variation. If this 10 ps is not desirable, then it can be eliminated by reading back the VCO core, capcode, and DACISET values and forcing these values to ensure the same calibration settings every time. The delay through the device varies from part to part and can be on the order of 60 ps. This part to part variation can be calibrated out with the MASH_SEED. The variation in delay through the device also changes on the order of +2.5 ps/°C, but devices on the same board likely have similar temperatures, so this will somewhat track. In summary, the device can be made to have consistent delay through the part and there are means to adjust out any remaining errors with the MASH_SEED. This tends only to be an issue at higher output frequencies when the period is shorter.