A High-Resolution 2-GHz Fractional-N PLL With Crystal Oscillator PVT-Insensitive Feedback Control

This letter presents a 2-GHz fractional-N phaselocked loop (PLL) with a high-precision delta-sigma digital-to-analog converter (DAC) to overcome the frequency deviation of a crystal oscillator due to manufacturing process, supply voltage, and temperature (PVT). The delta-sigma DAC with high power efficiency and linearity consists of a second-order delta-sigma modulator, a finite impulse response filter, and a lowpass filter. With the proposed PLL architecture, the frequency resolution can be lower than a few thousands of pulse per minute. The PLL is implemented in a 0.13-μm 1P6M CMOS process. With temperature from -40 °C to 80 °C, the measured results of 15 chips show that the frequency deviation of output frequency in PVT decreases from 1 to 0.002 ppm. The phase noise of PLLs is less than -126 dBc/Hz at 1-MHz offset at a carrier frequency of 1.99 GHz. The rms period jitter is below 1 ps at 1.99 GHz, while consuming a total power of no more than 10 mW.