A

Absolute Pull Range (APR) - The minimum lock range which can be achieved by a VCXO considering all VCXO internal tolerances and operating environments.

ACMOS - Advanced Complimentary Metal Oxide Semiconductor. This is a part of the Integrated Circuit Logic family .

Aging - The permanent change or shift in the operating frequency of a crystal over time. These are usually specified in parts per million per year (ppm/yr.) Aging typically decreases exponentially with time-3 to 5 ppm over 10 years can be expected.

Attenuation - Reduction of signal in transmission through a filter, usually expressed in decibels (dB).

B

Bandwidth (BW) - The difference between two cut off frequencies at a specified attenuation level (like 3dB).

C

Center Frequency (Fo) -The arithmetic mean between the high and low cut-off frequencies of a filter.

CMOS - Complimentary Metal Oxide Semiconductor. This type of device is in the Integrated Circuit Logic family.

Collpitts Oscillators - This Oscillator configuration utilizes the crystal from the base of the ground in the circuit. The bulk of the phase shift is provided by the capacitors and the balance is provided by the feedback path through the crystal. In this circuit the crystal is parallel-resonant with the series combination of the Colpitts capacitors, while loop gain is optimized with a base-emitter capacitor that is lower in value than the emitter-ground capacitor. In applications above 66 MHz it is a common practice to reverse the ratio to enhance additional feedback to the base.

Common Base Oscillators - The most complex of the oscillator designs. It uses conventional common-base rules and provides mid-range voltage gain and sinusoid output. This is typically used in devices that are designed to accommodate frequencies above 125 MHz and use crystals that operate on or above the fifth overtone.

Crystal cut - The actual plane of the crystal elements it relates to the crystalline axes of the quartz material being used. The cuts, like the common AT or BT cuts, determines the properties used in the finished product.

Crystal holder - A casing or housing which is used to both protect the crystal unit as well as to facilitate a solid electrical connection for the crystal.

Cycle-to Cycle Jitter - The deviation between periods of two adjacent cycles, used to detect large displacement failures. Measurement requires adjacent cycle capture; therefore, two successive cycle edges to collect the data.

D

DLD - DLD stands for drive level dependency. Used to measure the changes in a crystal's equivalent series resistance (ESR) or resonant frequency as it pertains to a varying drive level. These characteristics are used to determine crystal quality levels.

Drive Level - The RMS power provided by an oscillator circuit, which is induced into or dissipated by the crystal. The drive level can be measured in microWatts or milliWatts

Drive Level Correlation - The RMS drive level which is typically used during final test and inspection. It is typically used to determine the crystals parameters, like frequency or ESR, etc.

Drive Level Maximum - The maximum drive level, which when exceeded, is beyond the capabilities of the device and is beyond the specifications limits. When drive level exceeds specification levels, performance is both not recommended and not guaranteed. When critical applications call for a performance level which is close to the correlation drive level, it should be called to the attention of Ascend Engineering to review the specification and/or the application parameters.

Drive Level (Operational) - When a crystal is driven to a specific design application which is determined by a customer specification.

E

ECL - Emitter Coupled Logic.

Electrostatic Discharge (ESD) - Ascend suggests that the end user take all precautionary measures to be protected from electrostatic discharge damage. Ascend suggests the components be handled and mounted at static safeguarded workstations, which can prevent static build-up or static charge. These charges may occur when using conductive containers, conductive flooring, conductive wrist bands, grounding metal trays, or other similar activities.

EMC - Electro-Magnetic Compatibility.

EMI - Electro-Magnetic Interference caused by noise in digital circuit equipment.

ESD - Electrostatic Discharge. Precautions should be made to prevent or remove static build-up or charge. Suggestions include the use of grounding metal trays, conductive containers, and personnel by using conductive floors, conductive table mats and conductive wrist bands.

ESR - Equivalent Series Resistance of the crystal which is measured in Ohms at the series resonant frequency.

F

Filters - Device used to suppress spurious noise generated by digital equipment; also used to prevent external noise from being mixed with the signal. Can be used in avionics applications as well as AO equipment; computers; printers; AV, measurement, and medical equipment; electronic music, and medical. equipment.

Frequency - Cycles per second which are measured in thousands (kHz) or millions (MHz). Nominal Frequency, or the center frequency, is the frequency measured under nominal test conditions; for example, the nominal load @ 20 degrees C=/- 5degrees C.

Frequency Stability - In crystals- The maximum change or deviation relative to change due to influences in operating temperature. It is measured in parts-per-million (ppm).
-In Oscillators- The maximum change in the output frequency which is relative to calibration, operating temperature range, supply voltage range, vibration, shock, load variations, or aging. Also measured in parts-per-million.

Frequency Tolerance - The allowable deviation from the specified nominal frequency at a certain load capacitance. Sometimes frequency tolerance can be referred to as calibration accuracy; it is discussed as a percentage (%) differential or in parts per million (ppm).

Fuse Voltage Rating - The maximum voltage up to which a safe fault current interruption will occur. Consider the maximum effective voltage of the circuit.

Fuse Current Rating - The rated current of the fuse is a value greater than or equal to the specified rated value. Consider the maximum continuous operating current of the circuit and the influence of the ambient temperature.

Fuse Rated Breaking Capacity - The rated breaking capacity of the fuse, also known as the Interrupting Rating, is the short circuit current at which the fuse can blow (at the rated voltage) without destruction or arching being maintained. Consider the maximum possible fault current.

Fuse Interrupting Rating (IR) - The rated breaking capacity of the fuse, also known as the Rated Breaking Capacity, is the short circuit current at which the fuse can blow (at the rated voltage) without destruction or arching being maintained. Consider the maximum possible fault current.

H

HCMOS - High Speed Complimentary Metal Oxide Semiconductor. This convention is from the Integrated Circuit logic family and features high speeds and lower power consumption.

I

IMD or Inter modulation Distortion - A non-linear drive condition that is the main cause of IIMD in crystal filters

Insertion Loss (IL) - Power loss of a filter in the passband (expressed in dB). Zero dB reference shall be the point of maximum output of the filter unless it is specified otherwise.

J

Jitter - Short-term deviations found in a clock output signal which reference ideal position. Deviations can either lead or lag said ideal position. Jitter is measured in absolute value in pico seconds and specified as ps. Jitter is a measurement from the time domain. .Jitter has a Gaussean distribution, where width is recorded and termed as peak-to-peak jitter. In a crystal -controlled oscillator, jitter is associated with random noise and is uniformly distributed width deviations. See Cycle-to-cycle jitter and period jitter.

L

Linearity - The linearity requirements are application- specific and a function of the application. In a phase locked loop application , the linearity requirements may be very forgiving, while a frequency modulation application may be stringent. Linearity has a direct impact on costs; therefore, specifying needs is optimal. Specifying more-than needed requirements is not cost-effective.

Load Capacitance - The dynamic capacitance of an oscillator across the terminals. The typical Load capacitance is stated in conjunction with Frequency Tolerance, as to measure the sum load across the circuit, which can include an IC or transistor, capacitors, and other board-level components-each a factor in the composite circuit.

LVCMOS - Low Voltage Complimentary Metal Oxide Semiconductor, also from the Integrated Circuit logic family.

LVTTL - Low Voltage Transistor-to-Transistor Logic, in the Integrated Circuit logic family.

LVDS - Low Voltage Differential Signaling, in the Integrated Circuit logic family.

LVPECL - Low-Voltage Positive Emitter Coupled Logic, an Integrated Circuit logic family device.

M

Mechanical Shock - Usually discussed in reference to handling practices when carrying crystal and XO. The fragile nature of the crystal blanks, these devices requires precaution such as careful handling and rubber floor mats to absorb shock if dropped, helping to prevent damage to the devices. Examples of mechanical shock can be: broken crystals, broken interconnects, damaged packages, or broken seals.

Mode - Reference point to the specific overtone for achieving the oscillation in the crystal, typically referred as the fundamental- and the 3rd-, 5th--, or 7th- overtones. Fundamental mode frequency can be odd or even, but the overtones are always in odd numbered multiples.

Modulation Bandwidth - Specified as 3dB bandwidth in kHz, is many times called the "3 dB roll-off point."

Monolithic Crystal Filters (MCF) - High Q's and excellent temperature and aging characteristics that lend themselves to very narrow bandwidths and high selectivity. Product offers user with sharp cut-offs and low losses. The two pole monolithic filter is the basis for all packaged filters (as compared to a discrete filter: a single monolithic dual resonator replaces two discrete crystal units, a balanced transformer, and a trimmer capacitor). The net result is a smaller and more cost-effective device than the discrete crystal filter and uses fewer components and interconnects. This makes the MCF more reliable, while eliminating balanced transformers, reducing loss and improving stability.

Motional Capacitance - Characteristic most often specified in VCXO applications. It provides a key value t the electromagnetic circuit model and has direct impact on the pull ability within the circuit. Specified as C1.

Motional Inductance - Key value in Electro-Mechanical equivalent circuit model of a crystal. Specified as L1.

O

OCXO - Oven Controlled Crystal Oscillator that provides ultra stable frequency stability of +/-1ppm or better.

Operable Temperature - The ambient temperature range which a given device will operate; however, it is not necessarily a parameter that will meet all specifications.

Operating Temperature Range - Ambient temperature range which said device operates at a temperature range where performance is guaranteed. It is a key parameter, especially for VCXOs, as it has tremendous cost implications.

Oscillators- Device used to establish a reference frequency used for timing purposes. A typical application is the sequencing of events for a computer.

Output Load - The equivalent circuit to which an oscillator's output may be connected to, and accomplish all stated performance specifications. The Output Load can be specified electrically, as in 10 Ohms or 18 Picofarads (pF); or in Logic Units, like 10TTL. Ascend Engineering also suggests the engineering consideration to check each circuit for transmission line defects or strays.

P

Packaging Techniques - Any reference made to include the likes of component case size (ex. 5x7 ceramic), common industry package (ex. HC-49 or 32S12C or DIL-14), tape & reel specifications, barcoding, direction of feed, or the use of preferred boxing methods for shipments.

PECL - Positive Emitter Coupled Logic or Pseudo Emitter Coupled Logic. PECL devices are also an Integrated Circuit logic family.

Period jitter - The measurement of any non-adjacent population of cycles, which leads to the gross data that reflects the maximum difference of jitter within the sample taken. This measurement is critical in the detection of short-cycle failures-- a typically elusive failure mechanism that is a worst case jitter value.

Phase Noise - Short-term variations of a clock signal found in the frequency domain. Usually specified in dB below the carrier per Hz of bandwidth (dBc/Hz) or when excellent performance is required.

Pierce Oscillators - Integrated Circuit or transistor based crystal oscillator circuit which can be either a stand-alone or part of an even larger, more complex circuit. Pierce-type oscillators use an inverter to provide 180 degrees of phase shift, with the remaining 180 degrees being supplied by two pi capacitors. The loop gain can be optimized by specifying a lower output capacitance value than that of the input.

Poles - The two-pole monolithic filter is the basis for all packaged crystal filters. With the addition of coupling capacitors between pole sections, they can be cascaded to produce four, six, and eight or more pole filter responses.

ppm - Abbreviation for parts-per-million; normal unit of measuring for frequency deviation from nominal, like 1000ppm=0.1%, 100ppm= 0.01%, and 10ppm= 0.001%.

Programmable Oscillator - A crystal controlled oscillator which frequency is set by using fundamental crystal and an EPROM integrated circuit. Ascend uses a proprietary design and manufacturing technique to provide its customer with a complementary alternative and short lead time solution to fixed frequency devices.

Pullability (in crystals) - The change in frequency of a crystal in its response to a change in load capacitance. Usually measured in ppm levels, it is a function of the shunt capacitance and the motional capacitance of the crystal unit.

Q

Q (Quality Factor) - A description of the ratio of the crystal's equivalent circuit reactance and its resistance. This ratio will vary according to frequency, mode and/or holder type. This figure reflects the crystal's efficiency to convert energy.

Quartz - Silicon Dioxide (SiO2), which is synthetically grown, and is the basis for all Ascend frequency control devices.

R

Resonance Mode - In Resonance or Parallel Resonance modes of operation, the resonance mode needs to be specified to complete the circuit. Similarly, in the Parallel mode, Capacitance needs to be specified.

Ripple - The wavelike response in the passband of a filter that is recorded in dB. It is usually the excursion from highest peak to lowest valley.

Rise/Fall Times - The time that elapsed during a digital signal's transition from one output voltage or logic state, to another or opposite logic state. The measurement, found primarily at CMOS or TTL levels, is usually provided in nanoseconds (ns).

RMS jitter value - Jitter classification used to describe the jitter in SONET, Gigabit Ethernet, and Fibre Channel conventions. In such applications total system jitter is specified in either Unit Intervals (UI) or RMS units. The formula for the RMS value us Peak-to-Peak divided by 6.

S

SAW - Surface Acoustic Wave device, used as a filter or resonator to exploit the surface piezoelectric characteristics of quartz or other similar minerals.. Generally services the 82-470 MHz applications.

Shock Characteristics - Impulses such as half sine, square, sawtooth, and complex combinations thereof) that can occur in the field, These are due to the delicate nature of the quartz crystalrequiring isolation from equipment to minimize shock damage. We recommend the user to avoid over specification, since the elastic properties of the materials and the degree of isolation afforded b7y the equipment can decrease the normal potential of a shock.

Shunt Capacitance - Also referred to or called static capacitance. Symbol is Co. Measured in picoFarads (pF) from pin-to-pin.

SMD - Surface Mounted Device, connotes using a leadless device. The actual component , usually placed automatically on the board's surface, is without leads. Conversely, a leaded device-NOT SMD- would go through a board to be soldered in a pin-through-hole application.

SMT - Surface Mounted Technology The technology used when describing the assembly of printed circuit boards requiring leadless components.

Spurious Modes - Naturally occurring and unwanted oscillation modes found near the nominal frequency of a crystal. Usually specified in dB below the main resonance amplitude. One of he two basic problematic areas associated with crystal filters (along with non-linear drive level responses). These responses are caused by harmonic resonances normally occurring just above the desired resonances well as near harmonic overtone responses. The spurious region appears in the filter as narrow responses of reduced attenuation. Since MCF's must operate over a wide drive level range, each should be tested over expected drive level conditions.

Stand-by Mode - A control that completely turns off the circuit, as to reduce the power consumption in that circuit to microAmp levels.

Start-up Time - The actual time delay that occurs between the application of supply voltage (or resume from stand-by) to achieve the full operation of an oscillator within specified tolerances.

Start Voltage - Minimum supply voltage at which an oscillating circuit can operate, and is affected by all circuit elements-especially the integrated circuit.

Shape Factor - The ratio of bandwidths at two different levels of attenuation

Spurious Mode - Unwanted responses that occur in the filter due to resonant frequencies of the resonator other than the fundamental frequency.

Stop Band - The area of frequency where it is desirable to reject or attenuate all signals as much as practical. Also referred to as a reject band. This measurement is expressed as a range of frequencies attenuated by more than some specified minimum, such as 60dB.

Supply Current - The current flowing through an oscillator and its load circuit (from Vcc or Vdd to ground) under specified conditions (example, as typical or maximum). The current is measured in milliAmps (mA) and is typically stated as a maximum. It is a function of supply voltage, the oscillator circuit, the output circuit, the frequency, and the load.

Supply Voltage - The DC voltage that is applied to, or required by, an oscillator to achieve full operational levels.

Symmetry - Commonly referred to as Duty Cycle, symmetry is a measurement of an oscillator's output waveform that is above a reference voltage level as stated as a percentage of a full cycle. The reference voltage level for the symmetry measurement is typically 1.5V or TTL applications, or 50%Vdd for CMOS applications.

T

Tape & Reel - Packaging method that is typically selected when volume shipments and or surface-mounted products are required.

TCVCXO - Temperature Compensated Voltage Controlled Crystal Oscillator.

TCXO - Temperature Compensated Crystal Oscillator. The TCO is used to create a stable frequency reference over a prescribed temperature range. These devices can be used with either fixed or variable frequencies. As the fixed devices are manufactured to meet the specified frequency and to stay within a few parts per million for the life of the product. Lower cost TCXOs, used primarily in wireless equipment, can be used to meet the varying needs of the manufacturer, as to compensate for variables such as ambient temperature, voltage, or load environments.

Tri-state - This feature facilitates board level testing. The ability to force the oscillator output pin to a high-impedance state, utilizing the pin 1 control input; therefore, facilitating testing to Auto Testing Equipment (ATE) levels. A CMOS or TTL VCXO would require five (5) pins, while an ECL VCXO with complementary outputs and tri-state function (enable/disable) would require six (6) pins.

TTL - Transistor to Transistor Logic, found in the Integrated Circuit logic family.

V

VCO - Used in TV's and audio equipment because the signals need to be processed in synchronization with pilot signals transmitted from broadcasting stations.

VCXO - Voltage Controlled Crystal Oscillator. Absolute Pull Range (APR) devices are specified to meet performance requirements over all operating conditions. Also, some VCXOs can also be built to support specific requirements and perform in a variety of operating conditions.

Vibration - Generally classified asvPeriodc and Random. XO- Short cut term for a crystal oscillator, or clock, that utilizes a fixed frequency and is uncompensated. When considering an oscillator, Ascend recommends that the following factors be considered: Is the application fixed or modulated? What is the frequency of the application? What is the load that the oscillator will output into? And are the parts available in the case size or packaging required?