A MEMS Real-Time Clock With Single-Temperature Calibration and Deterministic Jitter Cancellation

Area of Science:

• Electrical Engineering
• Materials Science
• Physics

Background:

• Traditional real-time clock (RTC) systems often face challenges with frequency stability due to temperature variations.
• Microelectromechanical systems (MEMS) resonators offer potential for miniaturized and low-power timing solutions.
• Integrated circuits (ICs) are crucial for signal processing and compensation in advanced timing devices.

Purpose of the Study:

• To develop a highly stable and low-power real-time clock (RTC) system.
• To integrate a microelectromechanical system (MEMS) resonator with an advanced integrated circuit (IC) for frequency compensation.
• To analyze the effectiveness of a digital-to-time converter (DTC) in jitter suppression for MEMS-based RTCs.

Main Methods:

• A microelectromechanical system (MEMS) resonator with a -30-ppm/K temperature coefficient of frequency (TCf) was fabricated using a standard polysilicon process.
• Frequency drift compensation was implemented within the integrated circuit (IC) utilizing fractional frequency division.
• A low-power digital-to-time converter (DTC) was employed to reduce output jitter from approximately 1 μs_rms to less than 40 ns_rms.

Main Results:

• The system demonstrated a ±8-ppm output frequency stability after a single-point temperature calibration.
• Achieved remarkable low current consumption of approximately 800 nA from a 1.2-V supply.
• The digital-to-time converter (DTC) effectively suppressed deterministic jitter, validating its utility in this application.

Conclusions:

• The developed MEMS-IC based RTC system offers superior frequency stability and low power consumption.
• Fractional frequency division within the IC provides effective deterministic frequency drift compensation.
• The integration of a DTC is a viable strategy for mitigating jitter in MEMS resonator-based timing applications.