A digital PLL with a multi-delay coarse-fine TDC

Abstract

A 5GHz digital frequency synthesizer achieving a low noise for wireless RF application is presented. This architecture uses a multi-delay coarse-fine Time-to-Digital Converter (TDC) to achieve both the large detection range and fine resolution. A Digitally Controlled Oscillator (DCO) based on capacitive degeneration in LC-Tank is also implemented. The DCO achieves frequency quantization step of 300 Hz without any dithering. Simulated phase noise at 5 GHz carrier frequency is −125 and −151 dBc/Hz at 1 MHz and 20 MHz offset, respectively. The Digital phase-locked loop (DPLL) is realized in 90nm CMOS process and consumes 14mA from a 1.2V supply.