28
Clock oscillators are devices which generate the pulses
to control the timing and operation of logic circuitry. They
differ from other components used to control the timing of
logic circuits, such as quartz crystals and ceramic resona-
tors, in that clock oscillators need a power supply but no
additional exter nal circuitry to operate. Clock oscillators are
usually made by combining in a single package a frequency
control device such as a quar tz crystal, and a hybrid circuit
of resistors, capacitors, and either transistors or an inte-
grated circuit. The package is often either a welded steel
can or ceramic package her metically sealed which protects
the crystal and electronics from environmental effects and
also reduces the unwanted electromagnetic and radio-fre-
quency emissions which oscillators can generate.
OSCILLATION DEVICES
Various types of circuits can be used to generate tim-
ing wavef orms f or electronic devices. The simplest of these
is a simple circuit using capacitors, inductors and an active
element such as a transistor or operational amplifier. This
is an easy, low cost solution but the frequency is not very
stable due to temperature and individual component varia-
tions. A more stable circuit would utilize a ceramic resona-
tor, which has the advantage of better frequency toler ance ,
but resonators are only a v ailable in certain frequency ranges
and stability of ±0.5% is the best that can be achieved. If
better frequency stability is needed, then the most popular
method is to use a circuit which relies on the piezoelectric
proper ties of quar tz cr ystals to stabilize the oscillation.
If an alternating electrical field is applied to a cut and
polished quartz crystal, the crystal lattice will deform due
to what is is called the piezoelectric effect. At one par ticu-
lar frequency, which is determined by the geometry and
size of the crystal, vibration will occur much more easily
than at any other frequency. This is called the “resonant”
frequency. If an oscillation circuit is built around this crys-
tal, the mechanical vibrations can be used to control the
electrical oscillations very precisely.
AVX/Kyocera builds its high quality clock oscillators
from the substrate up. The whole module is hermetically
sealed into an all-metal welded package to protect it from
humidity. The case is directly grounded into a pin to help
minimize RF radiation and meet FCC’s EMI specifications.
A full range of clock oscillators are manufactured by
AVX/Kyocera. These extend from 1 MHz up to 72 MHz and
include TTL and HCMOS compatible drive levels. AVX/
Kyocera also offers special low power consumption clocks
for long life battery applications. (See char t page 28.) Ap-
plication specific designs f or critical requirements of toda y’s
high-speed, 32-bit microprocessors are available.
WAVEFORM
The diagram below shows a typical waveform of a
clock oscillator with an explanation of the parameters im-
por tant for correct selection of the appropriate device.
Often called the symmetry of a waveform, duty cycle is
a measure of how close to being equal the high and low
parts of a waveform are. A perfectly symmetrical waveform
will have duty cycle of 50%. We usually specify the mini-
mum and maximum variations of the duty cycle as, for
example: 60/40%. This is computed from the times shown
on the diagram below as A /A+B.
AVX/Kyocera Clock Oscillators
GENERAL DESCRIPTION
Cordless & Cellular Phones Output Features
Temperature Compensated Frequency (MHz)
KT11 12.8, 13.0, 14.4, 14.85, 15.36, 16.8, 19.2 1Vp-p/10kΩ /10pF Surface Mount
KT12 12.8, 13.0, 14.4, 16.8, 19.2, 19.68 1Vp-p/10kΩ /10pF Miniature Surface Mount
KT14 13.0, 14.4, 14.85, 16.8, 19.2, 19.44, 19.68, 19.8 1Vp-p/10kΩ /10pF Ultra Low Profile Surface Mount
VCO 200~2000 High Performance Surface Mount
Series Output Fan Out Output Level Features
Frequency (MHz) VOH Min VOL Max
TTL
K50 -HC* -C †8 to 68 50pF 0.9 VDD 0.1 VDD CMOS/TTL Drive
KXO -01 8 to 50 10 TTL 2.4 0.4 Cost Performance
KXO -HC* -T (KHO -HC* -T) 1 to 72 10 TTL 2.4 0.4 Versatile Drive Capabilities
HCMOS
K50 -HC* -C †8 to 68 50pF 0.9 VDD 0.1 VDD CMOS/TTL Drive
K50 -CS* -SE 8 to 50 15pF VDD-0.5 0.5 Low Power Consumption
KXO -HC* -C (KHO -HC* -C) 1 to 72 50 pF 0.9 VDD 0.1 VDD Versatile Drive Capabilities
386 -HC 24,32,40,50 7 TTL 0.9VDD 0.1 VDD Drives 80386
Low Voltage
K50 -3C (3.3V) 8 to 68 15pF 0.9 VDD 0.1 VDD Low Supply Voltage
†Will also drive TTL. See catalog for details – page 31.