Real time clock (RTC) integrated circuits are available from several mixed-signal semiconductor companies. One thing that is common among all of them is the requirement to utilize a resonator that can be divided down to 1Hz, allowing the RTC device to “count seconds”. Most RTC ICs feature a crystal oscillator that is clocked with an external 32.768kHz crystal. These crystals are low cost and are fairly accurate. The accuracy of the RTC is dependent mainly upon the accuracy of the crystal. Tuning-fork crystals have a parabolic frequency response across temperature and typically vary by 180ppm over the -40°C to 85°C temperature range. 180ppm translates to an error of approximately eight minutes per month. RTC oscillators have internal bias networks. The crystal should be connected directly to the X1 and X2 pins with no additional components, and should also be as close as possible to the X1 and X2 pins. A ground plane should be placed beneath the crystal, X1, and X2. Digital signal lines should be routed away from the crystal and oscillator pins. Low-power crystal-oscillator circuits can be sensitive to nearby RF interference, which can cause the clock to run fast. Consequently, components that radiate significant levels of RF should be shielded and located away from the crystal. Recent technological advances by Analog Devices and other RTC manufacturers improve the accuracy of the RTC over temperature by embedding a 32.768kHz crystal in the plastic package with the RTC device. The RTC device in this architecture features a TCXO that allows for initial accuracy better than ±5ppm, which translates to an error of less than a half second a day. Additionally, because the crystal is embedded in the package, the designer need not be concerned with PCB layout as described earlier in designs using external crystals. While this is a huge improvement over the traditional external crystal design, this architecture still has drawbacks. In applications subject to high moisture, shock/vibration, a crystal-based design can have problems with the oscillator starting or maintaining oscillation. Also, the RTC in a crystal-based design will experience increasing timekeeping error as the crystal ages. The TCXO in this architecture can flatten the error Vs. temperature curve, but cannot alter drift or aging-induced error. To address timekeeping in rugged environments, Analog Devices has introduced the all-silicon precision RTC, featuring a MEMs resonator. With forty seven times less area and 182 times less volume than that of 32.768kHz tuning fork barrel crystal, the MEMs resonator technology used in Analog Devices' precision RTC product family provides a significant advantage in size and packaging options. However, advantages that MEMS bring to this technology area do not end with size.