SiTime, Silicon MEMS Oscillators and Clock Generators

Silicon MEMS Timing Architecture

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MEMS-stacked-die-package

A MEMS oscillator combines a MEMS resonator die together with a programmable oscillator IC. Both die are packaged together in industry standard plastic packages.

As shown on the left side of the diagram below, SiTime has developed different types of MEMS resonators for different applications needs. The output frequency is configured by using a phase locked loop (PLL) that is located on the analog oscillator die.

 

SiTime-MEMS-Analog-Architecture

MEMS resonators are connected to the MEMS-specific circuit blocks on the analog IC and are driven through electrostatic excitation. A MEMS bias generator is used to bias the electrostatic transducers that are built in the MEMS die. The resonator sustaining circuit brings the resonator into mechanical oscillation.

Since MEMS devices have an inherent temperature coefficient (stability varies with temperature), most MEMS timing devices are compensated 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. In addition, the Frac-N PLL generates the output frequency which can range from 1 Hz to 625 MHz, depending on the specific device. On-chip one time programmable (OTP) memory is used to store the compensation and configuration parameters. Output drivers usually offer configurable drive strength, for best matching of transmission line impedances and to reduce system EMI.

SiTime's world class analog design team has the expertise to develop MEMS timing products with the best performance and features available in the market today.