摘要:
A PLL circuit (100) is described. The PLL circuit includes: a signal generator; and a spread spectrum modulator (112) coupled to the signal generator (110), where the spread spectrum modulator receives a control voltage (V CTRL ) as an input and provides a spread spectrum control voltage to the signal generator in response to the control voltage (V CTRL ). In one embodiment, the spread spectrum modulator includes at least one selector, where the at least one selector selects a plurality of voltage levels that correspond to a spread mode and percentage of spread for the spread spectrum modulator.
摘要:
A programmable logic device includes configurable phase-locked loop (PLL) circuitry that outputs multiple clock signals having programmable phases and frequencies. Each output signal is programmably selectable for use as an external clock, internal global clock, internal local clock, or combinations thereof. The PLL circuitry has programmable frequency dividing, including programmable cascaded frequency dividing, and programmable output signal multiplexing that provide a high degree of clock design flexibility.