Datasheet

range. Another role of Rd is to
reduce the current consumption and
noise radiation.
3. Causes of the change of
osciIlation frequency
When using CERALOCK
®
for appli-
cations that requires a precise oscil-
lation frequency, all the factors that
cause frequency change must be
taken into consideration and the
influence of these carefully evaluated.
Generally there are two major factors
causing the frequency change. These
are the resonant frequency change of
CERALOCK
®
itself and the change of
load capacitance C
L1
and C
L2
.
The causes of the resonant frequen-
cy change of CERALOCK
®
can be the
initial deviation of resonant frequen-
cy, temperature characteristics, long-
term aging characteristics and
soldering heat characteristics of
CERALOCK
®
. The change of load
capacitance C
L1
and C
L2
, can be
caused by the lC's input and output
capacitance or the stray capacitance
of the circuit board as shown in
Figure 8. lt is important to consider
how much oscillation frequency is
affected by these factors. The amount
of frequency change caused by stray
capacitance of the lC's input and out-
put terminals can be checked by
assembling circuits using a variety of
lC samples. The stray capacitance of
the circuit board varies according to
the length and the width of land figu-
re, number of layers, and material of
the circuit board. The frequency
change should be estimated through
measurement of the stray capaci-
tance and computer simulation.
Many of the important considerations
in using CERALOCK
®
for an oscilla-
tion circuit have been described
above. Other than the above, Murata
offers evaluation reports at web site
at www.murata.com for various lCs
and their reference circuits so that
you can obtain the optimum opera-
tion. There is also a free of charge
evaluation service for lC and
CERALOCK
®
. Y our local Murata
office or franchised distributor will be
pleased to respond to any inquiries.
Ref. Tech11
www.murata.com
Figure 7 - Oscillation characteristics when damping resistance Rd is changed.
Figure 8 - Factors that cause fluctuation of the load capacitance on the ciruit