Explanation of Crystal Units
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(1) It has the possibility that a crystal element fractures when an excessive shock and a vibration more than the regulation are added at the time of the conveyance or circuit board mounting. Be sure to do characteristic confirmation when a shock more than the regulation, a vibration are added.
(2) Ultrasonic-wave cleaning may cause deterioration of crystal units.
(3) Leave it and bend 0.5 or more mm from the foundation of the lead in the case of lead type.
(4) The deformation of the extreme circuit board sometimes brings about a pattern comes off, a terminal and electrode comes off, a crack in the solder. Be careful when you install it in the position where the curve of the circuit board appears greatly when you divide a circuit board after you mount it specially.
(5) Select the model whose shock is small as much as possible, and use it after confirmation in advance when you use an automatic loading machine.
(6) Compared with the lineups of JC-49/U, small crystal units ( HC-49U/S, HC-49USM, UM-1, SMD) are designed to have lower limitable level of drive, of 100µw and below. Prior to use, therefore the crystal current should be examined in an actually mounting circuit.
(7) The negative resistance of a circuit must be checked. Confirmation of negative resistance is possible according to Fig.6, goal of negative resistance is about 5 times of the resonance resistance.
(8) The Rd in the circuit diagram is indispensable when used in a C-MOS oscillation ciucuit (see Fig.5.). If this Rd is attahcedm the level of drive is kept within the specified value and stable oscillation frequency can be obtained.
(10) Cg and Cd should be used within the range of 10~30pF, if Cg and Cd are used below 10pF or above 20pF oscilltion may be easily affected by circuit performance, level of drive may increase, or negative resistace may decrease, thus failing in maintaining stable oscillation.
(11) The layout for crystal oscillation circuits should be arranged as short as possible.
(12) The stray capacitance between circuits and ground patterns should be reduced.
(13) Crossing of crystal oscillation ciucuit patterns over other circuit patterns should be avoided.
(14) If the circuit used are IC types, and IC manufacturers are different, Frequency, Level of Drive, and Negative Resistance should be confirmed.
(15) Overone oscillation circuits need additional consulation.
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