A novel structure for DCO PLLs with equivalent 16 bit digital phase quantization, digital loop filter and 18ps long-term jitter

This paper describes a new structure for Digital Controlled Oscillator Phase Locked Loops (DCOPLL) with fine quantization of the phase information, generic digital loop filter and digitally controlled crystal oscillator. It is particularly suited for applications in which high frequency resolution and low jitter are requested. The way in which the phase information is finely quantized allows the designer to choose any kind of digital loop filter, which transfer function best suits the application. This concept has been implemented in a 0.5µm digital CMOS technology, using a digitally controlled crystal oscillator (DCXO) and a VHDL based 3rd order loop filter. Measurement results show that long-term jitter is below 18ps.