This is a great process achievement by SiTime. They have managed to cure the problem of MEMS oscillators over temperature at the source—the MEMS itself. Kudos to the process engineers!
SiTime Corporation has introduced the TempFlat MEMS. Until recently, all MEMS oscillators used compensation circuitry to stabilize the output frequency over temperature. This new design eliminates temperature compensation, resulting in higher performance, smaller size, lower power and cost.
The basic architecture of a MEMS oscillator combines a MEMS resonator die together with an oscillator IC. As shown on the left side of the diagrams below, Si Time has developed different types of MEMS resonators for different applications needs. The output frequency, which can range from 1 Hz to 625 MHz depending on the specific device, is configured by using a phase locked loop (PLL) that is located on the analog oscillator die. On-chip one-time-programmable (OTP) memory is used to store the configuration parameters. Output drivers usually offer configurable drive strength, for best matching of transmission line impedances and to reduce system EMI.
MEMS Oscillator Architecture without Temp Flat Technology
Previous to Temp Flat MEMS technology, MEMS timing devices had an inherent temperature coefficient (stability varies with temperature) and this required the use of temperature compensation circuitry to meet precision timing specifications. A temperature sensor, a temperature to digital converter and a Frac-N PLL are used to perform temperature compensation, which result in devices that meet ±0.1 PPM to ±50 PPM frequency stability over temperature.
Read More: SiTime’s MEMS Resonators: An alternative to Quartz