Glossary - alphabet order - "O"

OCXO

Abbreviation for Oven Controlled X'tal (crystal) Oscillator. This type of crystal oscillator is equipped with a small constant-temperature oven in which crystal devices are set in order to provide more stability. With TCXOs, temperature changes are compensated to suppress frequency variation, while with OCXOs frequency drift is suppressed by preventing temperature change in kept at high temperature. Accordingly, OCXOs are used for equipment such as measuring systems and base station communications equipment, which require more high frequency stability than is possible with TCXOs.



Operating temperature range

This is the temperature range within which the specifications (parameter values) of crystal device can be guaranteed.



Operating voltage (Supply voltage)

This is the voltage applied to the VDD/VCC pins, defined as the voltage needed for continuous operation that meets the electrical characteristics.



Optic axis

The axis along the direction in which birefringence does not occur (light ray separation does not occur) in a birefringent crystal. This is the Z-axis that runs through the crystal's apex in a quartz.



Optical low pass filter

A light beam is separated into two beams (an ordinary beam and extraordinary beam) when a light beam passes through a birefringent crystal. The OLPF is used to eliminate flickering (also called as moire) revealed when using a striped pattern in the CCD or CMOS image-sensing device.



Ordinary ray

A light ray whose speed does not depend on its propagation direction in a birefringent crystal.
This light ray follows Snell's law. An extraordinary ray is a light ray oscillating within the surface (main section) defined by the optical axis and the propagation direction of incident light.
A normal ray is a light ray oscillating perpendicularly to this surface.



Oscillation circuit

See "crystal oscillation circuit".

Reference: Crystal oscillation circuit



Oscillation circuit parameter

These are the constants for elements that comprise a crystal oscillation circuit. The parameters differ according to the type of crystal unit, its frequency, and the type of IC being used.

Crystal oscillation circuit

Reference: Crystal oscillation circuit



Oscillation start-up time

This is the time between when the power supply voltage has reached minimum operating voltage after power-on and when the crystal oscillator starts and reaches stable oscillation.



Output enable

The output enable pin sets stop mode for output while enabling internal circuit operations to continue. It is implemented on a real time clock module or crystal oscillator for use while the system is in stop mode, so as to help reduce the system's power consumption.



Output fall time

This refers to the time (waveform's fall time) required for the transition of output waveform from high voltage (high level) to low voltage (low level). In the figure at right, this time is tf.

CMOS load output wave form TTL load output wave form

Reference: Output rise time



Output frequency

The output frequency is the frequency output from a crystal oscillation circuit or crystal oscillator.



Output load

This is the load applied to CMOS or TTL circuits connected to an output.



Output load condition

This indicates the type or power of the load connected to an oscillator. The calculation for 1 TTL is IOH = -40 µA and IOL = -1.6 mA, and that for 1 LS-TTL is IOH = 20 µA and IOL = 0.4 mA.



Output rise time

This refers to the time (waveform's rise time) required for the transition of output waveform from low voltage (low level) to high voltage (high level). In the figure at right, this time is tf.

CMOS load output wave form TTL load output wave form

Reference: Output fall time



Overtone mode

An overtone mode is a higher vibration order related (as an odd-numbered multiple) to the fundamental vibration order. Each crystal unit has an overtone order in addition to its fundamental order. The overtone order is used to achieve high frequency, which is difficult to be attained with design or fabrication using the fundamental order. Mostly, the third (three times the fundamental) overtone is used.

Third overtone mode (Reference) Fundamental mode



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