The accuracy of a real-time clock (RTC) IC is dependent on the accuracy of the crystal used and its temperature characteristics. Applications having a wide temperature swing result in less accuracy. A typical tuning fork crystal, for example, has an accuracy of ±20ppm at room temperature, or ±2 seconds per day. The same crystal slows down an additional 14 to 16 seconds per day at the temperature extremes of -40°C or +85°C.
A temperature-compensated crystal oscillator (TCXO) can mitigate the effect of temperature changes. Maxim's highly accurate TCXO RTC ICs provide accuracy to less than 0.3 seconds per day. Additionally, because the TCXO is placed in the same package as the RTC, an external crystal is not needed.
Some of Maxim's TCXO RTCs have a patented SYNC feature that allows the RTC to be synchronized to an external signal, such as a compensated powerline frequency. This synchronization allows the RTC to provide accurate time without having an on-board temperature compensation scheme.
Accurate MEMS-based Real-Time Clocks