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Ceramic
Resonator General Information
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Resonator products
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Ceramic
resonators implement the mechanical resonance of piezoelectric
ceramics (commonly Lead Zirconate Titanate) (PZT), that result
in different vibration behaviors (modes) depending on the
resonance frequency. Ceramic Resonator design utilizes this
ceramic substrate by applying two metal electrodes evenly
placed on both the top and bottom of the substrate. When voltage
is applied, vibration of the ceramic substrate occurs between
the electrodes. The thickness of the ceramic substrate determines
the resonant frequency of the resonator.
Ceramic
Resonators provide a viable alternative to Quartz Crystals
for oscillation frequency stabilization. Although Ceramic
Resonators inherently reduce the precision for which frequencies
can be controlled as compared to Quartz Crystals, and other
Quartz based products, the benefits of Ceramic Resonators
can outweigh these shortcomings in many applications:
1. Production Costs:
Because of the difference in materials as compared to Quartz
Crystals, Ceramic Resonators are more easily mass produced.
When using package size versus cost as the basis for comparison,
Ceramic Resonators are approximately 25 - 50% less expensive
to produce in the surface mount package category, and approximately
50 - 75% less expensive to produce in the though hole package
category as compared to Quartz Crystal products.
2.
Package Size:
Ceramic Resonators can be manufactured in a smaller packages
than their Quartz counterparts, thereby increasing their attractiveness
where board space is limited.
3.
Mechanical Ruggedness:
Ceramic Resonators handle shock and vibration better then
their Quartz counterparts.
4.
Component Count Reduction:
Most Oscilent Ceramic Resonator Series allow for inclusion
of built-in capacitors thereby eliminating the need for external
loading capacitors.
5.
Other Considerations:
Because of their use of mechanical resonance, in principle,
Ceramic Resonators are better equipped to handle fluctuations
in external circuit or power supply voltage, providing stable
oscillation without adjustment. Further, these characteristics
provide for a much faster rise times and are independent of
drive level considerations.
Understanding
the Oscillation Circuit
Rt:
Feedback Resistor:
A Feedback Resistor is used to determine the oscillation circuit
bias. The feedback resistance will contribute to instability
if it is too large by reducing feedback. Conversely, if it
is too small, increases in current will be realized thereby
reducing gain. Recent developments in IC design allows for
the integration of the feedback resistor in many cases.
C1/C2:
Loading Capacitor:
The Stability of the Oscillation circuit is largely determined
by the C1/C2 values. If the load capacitance is too high,
a stop in oscillation can be expected. If too small, unstable
oscillation will occur because of oscillation waveform distortion.
When comparing the same IC, oscillation circuits with lower
frequencies require higher capacitance.
Rd:
Damping Resistor (optional):
Abnormal harmonic oscillation can be suppressed using a dampening
resistor. The dampening resistor and load capacitors work
together as a low-pass filter to reduce gain in the MHz range
of oscillation.
Rb:
Bias resistor (optional):
A Bias Resistor can be utilized in the Ceramic Resonator Oscillation
Circuit to change the bias point when a reduction in IC gain
is required, or to suppress unstable oscillation. This may
be especially considered when a 3 stage buffered IC, or TTL
IC, is used. Oscilent Engineering can help with the circuit
design if needed.
Oscilent
Ceramic Resonator Products
Oscilent
offer a full range of industry standard Surface Mount and
Through Hole Ceramic Resonators both with and without internal
capacitors. For standard Operating Temperatures (-20°C to
80°C), and for Automotive applications (-40°C to +125°C),
Oscilent offers a wide range of frequencies and frequency
stability options. Additionally, our Engineering and Design
capabilities allow for custom design and characterization
requirements that meet the demands of most applications.
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