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Appendix F
Oscillator terms and application notes
Nominal frequency: The center or nominal output frequency of a crystal
Package: Crystal oscillators are packaged in various styles from lead through
holes to surface-mount types. Various sizes and functions are suitable for
different applications.
H Level
Frequency tolerance: The deviation from the nominal frequency in terms of
parts per millions (ppm) at room temperature. (25° ± 5°C)
Frequency range: The frequency band that the oscillator type or model can be
1/2 VDD DC
10% VDD DC
Operating temperature: Temperature range within which output frequency
and other electrical, environmental characteristics meet the specifications.
Storage temperature: The temperature range within which the unit is safely
stored (supply voltage not applied) without damaging or changing the
performance of the unit.
Frequency vs. power supply variation: Maximum frequency change allowed
when the power supply voltage is changed within its specified limits (typical
±10% in Vcc or ±5% change).
Supply voltage (Vdd max): The maximum voltage which can safely be
applied to the Vcc terminal with respect to ground. Maximum supply voltage
for TTL is 5.5V and for HCMOS is 6V.
Input voltage (VIN): The maximum voltage that can be safely applied to any
input terminal of the oscillator.
Output HIGH voltage (VOH): The minimum voltage at an output of the
oscillator under proper loading.
L Level
Frequency stability: The maximum allowable frequency deviation compared
to the measured frequency at 25°C over the temperature window, i.e., 0°C to
+70° C. The typical stability is ± 0.01% (±100 ppm).
Aging: The relative frequency change over a certain period of time. This rate
of change of frequency is normally exponential in character. Typically, aging
is ±5 ppm over 1 year maximum.
Figure 1
Fan out: The measure of driving ability of an oscillator, expressed as the
number of inputs that can be driven by a single output. It can be represented
by an equivalent load capacitance (CL) or a TTL load circuit consisting of
diodes, load resistor, and a capacitor.
Jitter: The modulation in phase or frequency of the oscillator output.
HCMOS/TTL compatible: The oscillator is designed with ACMOS logic with
driving capability of TTL and HCMOS loads while maintaining minimum
logic HIGH of the HCMOS.
Tri-state enable: When the input is left OPEN or tied to logic “l”, the normal
oscillation occurs. When the input is Grounded (tied to logic “0”), the output
is in HIGH IMPEDANCE state. The input has an internal pull-up resistor,
allowing the input to be left open.
Output logic: The output of an oscillator is designed to meet various specified
logics, such as TTL, HCMOS, ECL, Sine, Clipped-Sine (DC cut).
Supply current (Icc): The current flowing into Vcc terminal with respect to
ground. Typical supply current is measured without load.
Harmonic distortion: The non-linear distortion due to unwanted harmonic
spectrum component related with target signal frequency. Each harmonic
component is the ratio of electric power against desired signal output electric
power and is expressed in terms of dBc, i.e. -20dBc. Harmonic distortion
specification is important especially in sine output when a clean and less
distorted signal is required.
Symmetry or duty cycle: The symmetry of the output wave form at the
specified level (at 1.4V for TTL, at 1/2Vcc for HCMOS, or 1/2 waveform
peak level for ECL).
SYM =TH / T x 100 (%); See Fig. 1.
Phase noise: The measure of the short-term frequency fluctuations of the
oscillator. It is usually specified as the single side band (SSB) power density
in a 1 Hz bandwidth at a specified offset frequency from the carrier. It is
measured in dBc/Hz.
Rise time (Tr): Waveform rise time from Low to High transition, measured at
the specified level (20% to 80% for HCMOS, ECL, and 0.4V to 2.4V for
Standby: A function that temporary turns off the oscillator and other dividers
to save power. Logic “0” will enable stand by mode. The disable current at
stand by mode varies from few microamperes to tens of microamperes (5pA
typical). Because oscillation is halted, there is a maximum of 10 ms (same
amount of start-up time) before output stabilizes.
Output LOW voltage (VOL): The maximum voltage at an output of the
oscillator under proper loading.
Fall time (Tf): The waveform fall time from High to Low transition, measured
at the specified level (80% to 20% for HCMOS, ECL, and 2.4V to 0.4V for
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Specifications subject to change without notice
Appendix F Page 1