Fast & Energy Efficient Start-Up of Crystal Oscillators by Self-Timed Energy Injection

Crystal oscillators take a long time and, more importantly, a significant amount of energy to start-up. This article presents a self-timed energy injection technique to quickly start-up a crystal oscillator, for very low energy consumption. This is achieved without a power-hungry oscillator to provide the injection signal. The design considerations are discussed, and a prototype crystal oscillator using the proposed technique is integrated into a 22-nm fully depleted silicon-on-insulator (FD-SOI) technology. Connected to a 50-MHz crystal, the manufactured IC achieves a start-up time of 6 μs, for an energy consumption of just 3.7 nJ.