1960 E. Grand Ave., 2
nd
Floor,
El Segundo, California 90245
Phone: 310.955.5300
Fax: 310.955.5400
4.2. Measurement of the oscillation Allowance
The procedure of measuring the oscillation allowance is to place a resistance in series beside the crystal.
With this additional resistance, the amount of CI necessary
for creating oscillation can be measured. That means the
'allowance' for oscillation. The oscillation allowance is
indicated by the value of the additional resistance (ref.,
Negative resistance has the same meaning as oscillation
allowance).
Basically, the oscillation allowance required is at least
five (5) times the CI maximum. To prepare the Ra for
evaluation, please use as many resistors as possible from
more than 5 times CI (up to 10 times CI if possible).
Cut off the power to the circuit and add resistors
beginning with a low value, becoming progressively
higher. Monitor the wave form with the oscilloscope; the
circuit has allowance if it oscillates. Continue this
procedure, gradually increasing the resistance. The circuit will show no oscillation at an Ra condition. It means
the limit of the allowance is under the condition necessary for oscillation. So the previous resistance is the value of allowance.
That is to say,the circuit oscillated when the Ra was 470kΩ, it did not oscillate when the Ra was 510kΩ. In this case, 470kΩ
(actually -470kΩ) is the oscillation al1owance.
4.3. Actual data sampling
Provided an unusual value for RF is not chosen among the parameters for the oscillation circuit(Rf, Rd, Cg and Cd),
the circuit will work even if these are small variations in the values. Actually data sampling is done with varying Rd, Cg and Cd.
The best parameter will be confirmed by using a graph described on 3.1. which uses Cg and Cd for the X axis and drive
level and oscillation allowance for the Y axes. So, data should be collected using various values for Cg and Cd applied to
several Rd conditions. For the capacitance of Cg and Cd choose as many as possible from 5pF to 50pF. We recommend that
you use a data chart as follows:
Cd=Cg Drive Level Ra Max. (Oscillation Allowance) Comment
5pF
6pF
7pF
8pF
9pF
10pF
12pF
:
47pF
50pF
The main things to concentrate on are drive level and oscillation allowance. The other item is a comment concerning with any
problem with oscillation start up time, ete. When data sampling is finished, find the range which shows acceptable
characteristics by producing a graph.
5. Other circuits and frequencies
This document described the parallel resonance oscillation circuit using a C-MOS inverter device, the crystal is both tuning
fork and fundamental AT crystal type. This section will explain the other circuits and frequencies.
5.1. Series resonance circuit with C-MOS inverter
Usually, the series resonance circuit with a C-MOS inverter device is constructed as in the following figure:
(134 páginas)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comentários a estes Manuais