A 2.7GHz divider-less all digital phase-locked loop with 625Hz frequency resolution in 90nm CMOS

A divider-less all digital phase locked loop (ADPLL) with a high frequency resolution is implemented. All blocks excluding digitally controlled oscillator (DCO) and time to digital converter (TDC) are realized in standard digital design which consumes less power. The DCO core adopts an improved source-varactor LC resonant tank to achieve a 20KHz frequency resolution. With the help of an additional ΔΣ modulator, the final frequency resolution is 625Hz. This work is simulated in 90nm CMOS process technology and consumes 7.6mW (DCO occupies 97.4%) under the power supply of 1.2V.