Enhancing the Performance of Critical Electronic Applications
Temperature stability is a primary requisite in critical applications such as wireless systems, synchronous telecom and wireless networking, precision instrumentation and other applications that rely on frequency for timing executions. These critical applications require a precision reference timing source that maintains the same frequency over temperature and voltage fluctuations. Therefore, these systems utilize a special reference source called a TCXO (temperature compensated crystal oscillator) that includes temperature correction circuitry and is calibrated over temperature. The TCXO device provides superior temperature stability compared to a traditional crystal oscillator (XO) devices.
An example of an application that requires TCXO performance is the mobile phone. The mobile phone service providers must ensure that all users are provided with a consistent infrastructure to send and receive calls without any disturbances or call drops. Thus, every cell phone must have a TCXO device so that synchronization with the base station is constantly maintained. While determining the TCXO requirements, the engineer analyze the acceptable frequency variation and the sources of frequency variations expected in the system. Temperature variation is the most significant contributor to changes in frequency. The TCXO is temperature calibrated (corrected), and thus maintains ultra-low stability performance over the full temperature range.
Recently, SiTime’s MEMS TCXOs have met the tight performance requirements with stability as low as 0.5ppm over the -40C to +85C temperature range. This is a significant milestone for MEMS because the TCXO segment has only been available from the industry standard quartz crystal oscillators. SiTime’s TCXOs enable any frequency ranging from 1 to 220 MHz to be specified with 6 decimal places of accuracy which facilitates the user to customize the frequency to their specific requirements and boost the performance of their system. Furthermore, the MEMS TCXOs are available in any frequency, supply voltage, and package with much shorter leadtimes than quartz alternatives.
For applications that don’t require the ultra-low stability down to 0.5ppm, a VCXO or voltage controlled oscillator offers stability performance down to 10ppm and includes the added feature of fine-tuning the output frequency with an analog voltage or digital control signal supplied by the system. The VCXO assists in synchronizing the clock on the receiver with the clock on the transmitter to ensure that the two devices are locked without any data security risks. A Crystal Oscillator has limited fine-tuning capability (up to +/-250ppm) and tends to be more expensive when large pulling range is required. SiTime’s MEMS VCXOs provide the widest pulling range up to +/-1600ppm with extremely tight linearity of 0.1%.
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