Electronic frequency compensation of AlN-on-Si MEMS reference oscillators. (August 2016)

• Record Type: Journal Article
• Authors: Kourani, Ali; Hegazi, Emad; Ismail, Yehea
• Is Part Of: Microelectronics journal. Volume 54(2016)
• Page Start: 72
• Page End: 84
• Publication Date: 2016-08
• Subjects: 4G -- Wireless -- Temperature compensation -- Frequency compensation -- Phase noise -- MEMS -- TCXO -- Piezoelectric resonator -- Reference oscillator -- Sigma delta ADC -- Phase locked loop -- Temperature to digital converter -- Incremental ADC -- Temperature sensor; Microelectronics -- Periodicals; Microélectronique -- Périodiques; Microelectronics; Electronic journals; Journals - contents and abstracts; Periodicals; 621.3805
• DOI: 10.1016/j.mejo.2016.04.010
• Languages: English
• ISSNs: 0959-8324

Abstract

Abstract: In this paper we report on the design of a frequency compensation system for AlN-on-Si MEMS reference oscillator to replace temperature compensated crystal oscillators (TCXOs) in cellular handsets. A 76.8 MHz, 105 ppm Temperature Stable, AlN-on-Si MEMS Oscillator is designed to demonstrate the frequency compensation scheme. Double layers of SiO 2 are used for passive temperature compensation. The oscillator consumes 850 μA, with phase noise of −127 dBc/Hz at 1 kHz frequency offset. Temperature drift errors and initial frequency offset of ± 8000 ppm are combined and further tackled electronically. A simple digital compensation circuitry generates a compensation word to a 21-bit MASH 1-1-1 ΔΣ modulator included in LTE fractional N-PLL for frequency compensation. Temperature is sensed using 4.6 μA, 11.5 bit temperature to digital converter TDC with resolution of 0.1 °C in 100 ms conversion time. The paper presents the first AlN-on-Si oscillator platform with ± 0.5 ppm frequency stability over temperature ranges from −40 °C to 85 °C. The system runs on 1.8 V supply in 32 nm CMOS.