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Notes for Crystals unit applicationsposition: Home > How to order > Notes for Crystals unit applications

Compared with the lineups of HC-49/U, small crystal units (HC-49US,HC-49US/SMD,UM-1, UM-5, SMD Type) 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.(See Fig.8.)

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The negative resistance of a circuit must be checked. Confirmation of negative resistance is possible according to Fig.7. A goal of negative resistance is about 5 times the resonance resistance

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The Rd in the circuit diagram is indispensable when used in a C-MOS oscillation circuit. (See Fig9.) If this Rd is attached, the level of drive is kept within the specified value and stable oscillation frequency can be obtained.

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Cg and Cd should be used within the range of 10-30pf, if Cg and Cd are used below 10pF or above 30pF,oscillation may be easily affected by circuit performance, level of drive may increase, or negative resistance may decrease, thus failing in maintaining stable oscillation.

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The layout for crystal oscillation circuits should be arranged as short as possible.

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The stray capacitance between circuits and ground patterns should be reduced.

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Crossing of crystal oscillation circuit patterns over other circuit patterns should be avoided.

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If the circuits used, IC types, and IC manufacturers are different, frequency, level of drive, and negative resistance should be confirmed .

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Overtone oscillation circuits need additional consultation.