A Low-Jitter Synchronous Clock Distribution Scheme Using a DAC Based PLL

A low-jitter clock is essential to achieve high performance in a large scale system of distributed sensors. We propose to use a low cost DAC, VCXO and FPGA counter to generate distributed synchronous clocks. The new system called digital distributed synchronous clock (DDSC) can reduce the jitter to 14.6 ps, a 60% reduction from 36.5 ps in a traditional PLL. When these two clocks are used as the source for a 24-bit ADC system, the result shows that DDSC makes the total harmonic distortion (THD) decrease dramatically from -106 dB with PLL to -117 dB.