Glossary of Oscillators terms

/Glossary of Oscillators terms
Glossary of Oscillators terms 2016-10-26T12:16:06+00:00

Glossary of Oscillators Terms

Aging

A systematic average change of an oscillators output frequency as a function only of time. It does not include effects of changing environments

Calibration or Adjustment Tolerance

The setting tolerance is the maximum allowable deviation from the nominal frequency at 25°C +- 3°C. It is normally specified in parts per million (ppm)

Duty Cycle

The percentage of each period that a signal is in logic high. This parameter is measured at a specified voltage treshold or at a percentage of the output waveform amplitude

Fall Time

The waveform fall time from high to low transition

Frequency Stability vs Temperature

The maximum allowable frequency deviation compared to the measured frequency at 25°C over the temperature window, i.e., 0° C to +70° C.

Frequency Tolerance

The maximum allowable frequency deviation from a specified nominal frequency at ambient room temperature (25°C ± 2°C). Frequency tolerance is expressed in parts per millions (ppm).

Input Current

The amount of current consumption by an oscillator from the power supply, typically specified in milliamperes (mA)

Jitter

The modulation in phase or frequency of the clock oscillator output

Linearity

The departure from a straight-line relationship of control voltage to output frequency

Load (fan out)

The capacity of the oscillator to drive other devices

Nominal Frequency

The frequency for which the crystal/oscillator is designed and to which it is tuned.

Operating Temperature Range

This is the temperature range over wich the quoted temperature-stability is specified

Output Level

The maximum or minimum voltage at an output of the oscillator under proper loading

Output Load

The characteristics of the circuit connected to the output. Normally this specification will be used as part of the performance specification.

Output Logic

The output of an oscillator is designed to meet various specified logic states, such as TTL, HCMOS, HCSL, LVDS, LVPECL, Clipped Sine Wave , True Sine Wave.

Overall Frequency Stability

The maximum allowable frequency deviation compared to the measured frequency at 25°C inclusive of 25°C tolerance, operating temperature range, input voltage variation, load change, aging, shock and vibration.

Phase noise

The ratio of the power density of one phase modulation sideband to the total signal. It is usually specified as the single side band (SSB) power density in a 1Hz bandwidth at a specified offset frequency from the carrier. It is measured in dBc/Hz

Pullability

The frequency shift of a VCXO as a function of control voltage

Rise Time

The rise time of an oscillator is defined as the transition time of the output wave form from a low to a high state. The transition time is measured between 90% and 10% of the falling edge of the switching wave form for TTL and CMOS devices

Start-up Time

Start-up Time is the time taken for an oscillator waveform to stabilise within specification after power is applied.

Storage Temperature Range

The temperature range in which the oscillator can be stored without damage, i.e. it will resume operation as normal once it is restored to within its operable temperature range

Supply Current

The current flowing into Vdd terminal with respect to ground. Typical supply current is measured without load.

Supply Voltage

The maximum voltage which can safely be applied to the Vdd terminal with respect to ground.

Symmetry (Duty Cycle)

Oscillator symmetry refers to the ratio between the time taken for a full cycle and that taken for a half cycle. For TTL output level oscillators these values are measured at +1.4 Volt, and at ½ VDD level for CMOS, HCMOS and Universal oscillator outputs.

Temperature Stability

Deviation from the nominal frequency including the frequency deviations due to manufacturing process, temperature, power source variation and load variation

Tri-state function

The tristate function allows the oscillator to be isolated from the circuit upon application of a command signal. When this feature is activated, the output of the oscillator is in tristate mode. The tristate mode allows the customer to remove the oscillator from their circuit without physically removing it. Useful for tuning, testing or trouble shooting their board.