A spread-spectrum clock generator with direct VCO modulation in open-loop

A new topology is proposed to achieve a center-spreading SSCG. It employs a new spread filter, consisting of two capacitors and a resistor. The modulated triangular waveform is formed at the center of the control voltage coming from the segregated PLL. A definite advantage is that the spreading behavior does not affect the bandwidth of the PLL. Moreover, the modulation filter consumes smaller chip area because a larger resistor can be utilized for the required bandwidth.

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