New spread spectrum clocking techniques: For improved compatibility with cellular and wireless subsystems

Spread spectrum clocking is an established technique for reducing electromagnetic interference arising from clocking signals. Though effective for reducing interference with other devices, SSC can increase the interference with radio receivers inside the device itself. New SSC techniques have been developed to reduce this internal interference while retaining the external interference benefits. Laboratory measurements and test chip results show significant reduction in radio interference. The techniques are applicable to switching voltage regulators and high-speed digital computing and communications systems.