MEMS resonator integrates with oscillator circuits

SiTime has entered the resonator market with a MEMs device that can be integrated into semiconductor devices and oscillator modules.

When it comes to digital circuits and communications technologies, timing is everything. A little jitter or long latency can ruin your day. Many microcontrollers, ASICs, SoCs, and wireless systems rely on quartz resonators to provide the base frequency for their clocks. While crystal resonators serve many applications, they’re no aren’t the only option, especially where stability over time and temperature are critical. SiTime, a company known for precision timing. Has entered the resonator market with a MEMS device.

SiTime has been manufacturing MEMS resonators for some time but has integrated them with oscillator circuits and a phase-locked loops to create complete oscillators such as the SiT9501. The integrated device consists of a resonator die and an analog-circuit die. Now, engineers can integrate the resonator into their own circuits.

Because MEMs devices are created using semiconductor processes, a MEMs resonator is much smaller than a crystal resonator. SiTimes’ ApexMEMS resonator’s die is just 0.42 mm² in size. The device has four terminals of which two are not connected. The two functional terminals connect to a low-swing AC excitation signal, just like a crystal resonator. Semiconductor companies and timing-module manufacturers can integrate the ApexMEMS die into their designs.

Both MEMS and crystal resonators must operate in a vacuum, and creating that vacuum part of the fabrication process. With MEMS, creating the vacuum takes place with the die is in wafer form. Application note
SiTime’s MEMS First and EpiSeal Processes explains the steps.

According to Sevalia, the ApexMEMS resonator is available in several frequencies that typically cover 1 MHz to 100 MHz, including 24 MHz and 25 MHz with stability from 50 ppm to 20 ppm. SiTime company does not specify the frequencies online. For that matter, the datasheet isn’t online. It’s available only to qualified high-volume semiconductor companies and module manufacturers.