A Quick Startup Technique for High- $Q$ Oscillators Using Precisely Timed Energy Injection

Abstract

High-quality ( $Q$ ) oscillators are notorious for being extremely slow during startup. Their long startup time increases the average power consumption in duty-cycled systems. This paper presents a novel precisely timed energy injection technique to speed up the startup behavior of high- $Q$ oscillators. The proposed solution is also insensitive to the frequency variations of the injection signal over a wide enough range that makes it possible to employ an integrated oscillator to provide the injection signal. A theoretical analysis is carried out to calculate the optimal injection duration. As a proof-of-concept, the proposed technique is incorporated in the design of crystal oscillators and is realized in a TSMC 65-nm CMOS technology. To verify the robustness of our technique across resonator parameters and frequency variations, six crystal resonators from different manufacturers with different packagings and $Q$ factors were tested. The implemented IC includes multiple crystal oscillators at 1.84, 10, and 50 MHz frequencies, with measured startup times of 58, 10, and 2 $\mu \text{s}$ , while consuming 6.7, 45.5, and 195 $\mu \text{W}$ at steady state, respectively. To the authors’ best knowledge, this is the fastest, reported startup time in the literature, with >15 $\times$ improvement over prior art, while requiring the smallest startup energy (~12 nJ).