Spread spectrum clock generator with hybrid controlled oscillator

A spread spectrum clock generator (SSCG) with a hybrid controlled oscillator (HCO) is presented. By using the proposed HCO, the modulation ratio of an SSCG can be made insensitive to process, voltage and temperature variations without a SigmaDelta fractional-N phase-locked loop. The simulated modulation ratio sensitivities are as low as - 1.3%/100degC and 7.0%/V for temperature and V_DD, respectively. The SSCG IC, designed in a 0.18 m 1P4M CMOS process, operates from 40 to 90 MHz and consumes 5.5 mA from a 1.8 V supply voltage.