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1、技术术语01：NOsignaloutputfromthecrystal? 1-1. PleasemeasurethesignaloutputbytwoterminalsofthecrystalusingOscilloscopeorFrequencyCounter.Ifthereisno signaloutput,pleasefollowstep1-1tostep1-4toexecutetheexamination.Ifthereissignaloutputfromout-terminalof thecrystal(Xou
2、t),butnosignaloutputfromthein-terminal(Xin),pleasecheckthecrystalfollowingstep1-5tostep1-6. 1-2. Pleaseuninstallthecrystalandtestitsfrequencyandloadcapacitancetoseewhethertheyvibrateandmeetyour specificationsusingaprofessionaltestingmachine.Youcanalsosendittoyour
3、suppliertohavethemtestitforyou. 1-3. Ifanyofthefollowingsituationshappen,thecrystaldoesn’tvibrate,itsloadcapacitancedoesn’tmatchyourspecification, orthereisahugegapbetweencurrentfrequencyandyourtargetedfrequency,pleasesendthecrystaltoyoursupplierto conductQua
4、lityAnalysis.Ifthefrequencyandloadcapacitancemeetyourspecifications,wewillneedtoconduct EquivalentCircuitTest. 1-4. EquivalentCircuitTest 1-4-1.Generally,theoscillationcircuitofMicroprocessorderivesfromColpittscircuitshowingbelow:Picture1CdandCgareexternallo
5、adcapacitances,whichhavebeenbuiltinthechipset.(PleaserefertotheSpecificationsofthechipset)Rfisthefeedbackresistancewith200KΩ~1MΩ.It’sbuiltinthechipsetgenerally.RdistheLimitResistorwith470Ω~1KΩ.Thisresistanceisnotnecessaryforcommoncircuitbutonlyforcircuitshavinghighpowers
6、upply.1-4-2.Astableoscillationcircuitrequiresanegativeresistanceanditsvalueshouldbeatleastfivetimesofthecrystalresistance.Itcanbewrittenas
7、-R
8、>5Rr.Forexample,toacquireastableoscillationcircuit,thevalueofnegativeresistanceoftheICmustbeunder–200Ωwhenthevalueofthecrystalres
9、istanceis40Ω.1-4-3.“Negativeresistance”istheyardsticktoevaluatethequalityofanoscillationcircuit.Undersomecircumstancessuchasaging,thermalchange,voltagechange,andetc.,thecircuitmightnotoscillateifthevalueof“Q”islow.Thus,it’sveryimportanttomeasurethenegativeresistance(-R)f
10、ollowingtheinstructionsbelow:(1)Connecttheresistance(R)withthecrystalinseries(2)AdjustthevalueofRfromth
