A symphony in quartz: Page 2 of 3

April 11, 2017 // By Michael Fischer, Epson Europe Electronics GmbH
A symphony in quartz
The more complex a musical piece and the larger an orchestra, the more urgent the need for a good maestro. In the internet of the future, the equivalent of a maestro or a metronome is called the master clock, which conducts the rhythm of all network nodes. Each node however needs its own perfect sense of timing.

OCXOs are excellent for maintaining stability across the entire temperature range; furthermore, their sensitivity to airflow is minimal. Although economical in comparison with atomic clocks, due to their complex structure they are still large and usually power-hungry. A future alternative could therefore be temperature-compensated crystal oscillators (TCXOs). These consist of a voltage-controlled crystal oscillator (VCXO) and a temperature-dependent voltage regulator.

TCXO basics: Circuit and characteristic.

TCXOs – a future alternative

In the past, developers often didn’t consider TCXOs for high-precision applications due to their high sensitivity to airflow and their lower temperature stability. Today, however, some types achieve stabilities of ±100 ppb at -40 up to +85 °C – a scale within which some of the smaller OCXOs also operate. Their sensitivity to airflow has also been significantly improved.

Epson is one of the pioneers in this field with its patented DoubleSeal technology. In the TCXOs in their “G series”, the crystal is double encased in order to isolate it from external influences. The temperature sensor and the crystal are also in close proximity to each other, which has a positive influence on compensation. As a result of these features, the accuracy of modern TCXOs today is perfectly adequate for many wireless and wired transmission standards.

And since they also use little power, TCXO’s are an attractive option for all mobile applications. This makes them more than just a substitute for what has been tried and tested, because for developers they serve as a new instrument that can be employed as required to orchestrate their circuitry.

TCXO Progress: Conventional double encased crystal (left) in comparison with Epson’s double seal architecture (right).

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