Serializer/deserializer (serdes) lanes with lane-by-lane datarate independence

Abstract

A circuit and method enables multiple serializer/deserializer (SerDes) data lanes of a physical layer device (PHY) to operate across a broad range of diversified data rates that are independent from lane to lane. The multiple SerDes data lanes may operate at data rates independent from one another. A single low frequency clock is input to the PHY. A frequency of the single low frequency clock is increased via a common integer-N phase-locked loop (PLL) on the PHY to produce a higher frequency clock. Each of the SerDes data lanes is operated, independently, as a fractional-N PLL that employs the higher frequency clock. Use of the common integer-N PLL enables modulation noise of the fractional-N PLLs to be suppressed by moving the modulation noise to higher frequencies where a level of the modulation noise is filtered, avoiding use of high risk noise cancellation techniques.