Renesas has 2 different types of spread spectrum: down spread and center spread. Center spread modulates evenly around the clock frequency while down spread modulates below the clock frequency. The type of spread used depends on the specifications of the clock destination. Some destination chipsets have a maximum clock frequency specification that cannot be violated, so in these cases down spread should be applied. In applications where the destination chip can accept +/- ppm clocks, center spread should be used.

