摘要 : Crystal oscillators(XOs)provide a high-precision reference frequency but have a long startup time,which severely increases the average power consumption in duty-cycled systems.This paper proposes a fully-digital low-cost two-step ... 展开 Crystal oscillators(XOs)provide a high-precision reference frequency but have a long startup time,which severely increases the average power consumption in duty-cycled systems.This paper proposes a fully-digital low-cost two-step injection technique,by using a successive approximation register(SAR)based auto frequency control(AFC)loop,to speed up the startup behavior of XOs.A theoretical analysis is carried out to determine the optimum injection time and design low-power XOs.Fabricated in a 65 nm CMOS process,the proposed 12 MHz fast startup XO occupies an active area of 0.02 mm^(2) and achieves a startup time less than 35μs.The XO power consumption in the steady state is 40μW from a 1.0-V supply,with a startup energy of 17.2 nJ. 收起