A Fully Differential 40 MHz Switched-Capacitor Crystal Oscillator with Fast Start-Up

This paper introduces a switched capacitor crystal oscillator as a fully differential alternative to the widely used single ended Pierce oscillator. The presented 40 MHz oscillator consumes 55 mu W during steady state operation at a 0.8 Vpp amplitude and a 6 pF load capacitance. Fast start-up, in typically 12 mu s and consuming a start-up energy of 8 nJ, is achieved by self-timed energy injection, without requiring an additional start-up oscillator. The oscillator is realized in a 22nm FD-SOI process.