A Fully Integrated Spread Spectrum Clock Generator Using a Dual-Path Loop Filter

A fully integrated spread spectrum clock generator (SSCG) using the VCO direct modulation was presented. The dual-path loop filter in the phased locked loop was employed to reduce the required area of capacitance in the filter by using another charge pump circuit. In the meantime, the third charge pump was used to achieve the triangle modulation. The proposed circuit had been fabricated by TSMC 0.35 mum . The clock rate from 50 MHz to 480 MHz with center spread spectrum ratios with 0.5%-2% was verified. The size of chip area was 0.82times0.8 mm² including the loop filter and the power consumption was 27.5 mW at 400 MHz.