Krystaly, Hradec Králové, a.s.

Terms, definitions and characteristics

Oscilátors types
 CXO ( PXO, MXO ) Single crystal oscillator,
has frequency stability of the crystal units
 VCXO Voltage controlled crystal oscillators,
can change the oscillation frequency with external voltage
 TCXO Temperature compensated crystal oscillator,
compensated for frequency changes caused by the external temperature
 OCXO Oven control crystal oscillator,
includes a temperature stabilized resonator

 Nominal frequency fo
 ( Output frequency )
Nominal value of the frequency described in specifications. It is the output frequency at the standard temperature (usually 25oC), specified power supply voltage and load.
 Frequency stability  [ppm] The frequency range before and after specific ambient conditions such as temperature, power supply input variations, load variations, operation time (aging, long-term stability), etc.
 ( Long-term stability )
The frequency deviation with the lapse of time during normal operation
 Frequency stability vs.
 supply voltage
[ppm/V] Frequency deviation when the power supply input voltage is varied.
 Frequency stability vs.  mechanical environment [ppm] Specified by the deviation before and after shock, dropping, sine wave vibration, constant acceleration, etc. applied.
 Frequency stability vs.
[ppm] / Z
Frequency deviation when the load conditions have varied from the standard value.
 temperature range
[ °C ]
The temperature range which the oscillator can safely operate. The frequency tolerance cannot be maintained outside the specified limits.
 temperature range
[ °C ] Maximum absolute temperatures allowed in the discharged state. Exposure to temperatures outside these limits may result in damage.
 Supply voltage [ V ] The DC input voltage necessary for oscillator operation.
 Input current [ mA ] The amount of current consumption by an oscillator from the power supply.
 (for VCXO type)
[ V ] This range indicates the width of output frequency that can be adjusted by control voltage.
 Start-Up time [msec],
The specified time from oscillator power-up to the time the oscillator reaches steady state oscillation.
 Logic levels [ 0, 1 ] Defined as the Output Voltage Logic High or "Logic 1" and the Output Voltage Logic Low or "Logic 0".
 Rise time ( Tr ) [ µs ] The time taken for the output waveform to change from the low voltage level to the high voltage level.
 Fall time ( Tf ) [ µs ]
The time taken for the output waveform to change from the high voltage level to the low voltage level.
 Duty cycle
 ( symmetry )
[ % ] Measured at +1.4V for TTL oscillators and ½ Vdd level for universal, HCMOS and CMOS oscillators, this is the ratio of full and half cycles.
 Internal Trim   This range indicates the width of frequency that can be adjusted by a trimmer built in the oscillator.
 Phase noise   The frequency domain measure of short term frequency stability of an oscillator.
 Short term stability   The random fluctuations of the frequency of an oscillator over short periods of time.


Measuring circuit

  • Cliped Sine

CL = 10 pF (including fixture and probe capacitances)
RL = 10 kΩ
  • CMOS

CL = 10 pF (including fixture and probe capacitances)
  • TTL

CL = 15 pF max (including fixture and probe capacitances)
*T.P = Test Point


Other courses

  • Output waveform

  • Phase noise

  • REFLOW diagram



Hradec Králové, a.s. 
Okružní 1144 
500 03 Hradec Králové 3 
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