Breakthrough in fast start technology of Autocorrection for phase error of crystal oscillator

The fast start technology of Autocorrection for phase error of crystal oscillator breaks through the starting time of crystal oscillator, which affects the time interval between data transmission and transmission of the system, and plays a decisive role in the power consumption of the system in duty cycle mode. With the rapid development of IoT devices and the popularization of low-power application scenarios, the role of quickly starting crystal oscillators is crucial.

Technical concept of Autocorrection of phase error

It is reported that the reference clock generated by the high-frequency crystal oscillator belongs to the module with cycle on, providing reference frequency for other modules in the system. Therefore, the length of its startup time has a significant impact on the power consumption of the duty cycle working system, which is 300 μ A startup time of more than s can increase the power consumption of low-power Bluetooth systems by 15%. Therefore, the start time of the reference clock is a bottleneck that limits the further reduction of system power consumption.

For high-frequency crystal oscillators with long start-up time and injection efficiency issues, the currently most efficient co frequency injection technology still faces some thorny issues. The same frequency injection technology requires an on chip injection signal source with precise frequency (error<5000ppm), but in practice, the frequency of this signal source cannot be very precise and stable due to the influence of PVT, and there is a frequency deviation between it and the intrinsic oscillation frequency of the crystal, also known as frequency deviation. The frequency offset will be integrated into phase difference during the injection process. As this phase difference continues to accumulate, the injection efficiency will gradually decrease, and even inhibit crystal activation. If we want to achieve an on chip injection signal source with ultra-high accuracy (<1000ppm), it means that the design difficulty and required control words will increase sharply, and the trim cost of the chip during mass production will be difficult to bear. Therefore, how to achieve efficient energy injection and rapid start-up of crystal oscillators under large frequency deviations has become a key factor in solving this problem.

Fast Start Crystal Oscillator Chip Based on Phase Error Autocorrection Technology

To solve the problem of startup time and injection efficiency of high-frequency crystal oscillator, the team proposed a fast startup high-frequency crystal oscillator chip architecture based on phase error Autocorrection technology. This chip continues to use the most efficient energy injection startup technology at present, proposes the concept of Autocorrection of phase error for the first time, and applies the single ended energy injection technology in the design of high-frequency crystal oscillator for the first time. Its internal circuit detects the phase error between the injected signal and the crystal oscillation signal and Autocorrection while injecting energy into the high-frequency crystal. After chip testing verification, under high frequency offset injection conditions of up to 10000ppm (twice the theoretical limit), the actual startup time of this chip is only 17.5 μ s. Reduced the startup time under this condition by 249 times. Compared with traditional dual ended energy injection technology, its startup time hardly fluctuates with injection frequency error (with a deviation of only 1.27%).

This work pioneered the concept and technology of single ended injection, which contributes to a deeper understanding of the starting principle of crystal oscillators and provides important insights and new ideas for the design of fast starting crystal oscillators.

It is reported that the research team has been committed to the research and design of digital analog hybrid integrated circuits such as fast start crystal oscillators, temperature sensors, and phase-locked loops. This research achievement has achieved a breakthrough in the field of fast start crystal oscillators for IoT applications, which is of great significance for further reducing the power consumption of systems such as IoT and low-power Bluetooth.