Electronic timing functions are traditionally provided by oscillators based on quartz-crystal resonators, although microelectromechanical-systems (MEMS) oscillators are being applied more often in applications once dominated by quartz-crystal oscillators. MEMS oscillators use mechanical structures, such as miniature tuning forks, to achieve resonant frequencies. MEMS devices are fabricated from silicon semiconductor materials and can be made smaller and operate with less power consumption than quartz crystal oscillators.
In addition, with the application of spread-spectrum techniques, as in the case of the SiT9005 MEMS oscillator from SiTime, they can even achieve a significant reduction in electromagnetic interference (EMI) compared to quartz crystal oscillators.
As signal sources, clock oscillators can leak enough EM energy to cause EMI and radio-frequency interference (RFI). In some cases, when clock signal power is high and with fast rise/fall times, sufficient radiation can be generated which can interfere with nearby circuits and/or equipment. Because of this, the FCC sets maximum EMI levels which all electronic equipment must fall below. The SiT9005 helps reduce EMI without additional shielding by using spread-spectrum clock modulation, as well as programmable clock signal rise/fall times.