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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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HT45F75 датащи(PDF) 44 Page - Holtek Semiconductor Inc |
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HT45F75 датащи(HTML) 44 Page - Holtek Semiconductor Inc |
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44 / 190 page  Rev. 1.10 �� De�e��e� 1�� �01� Rev. 1.10 �5 De�e��e� 1�� �01� HT45F75 Body Fat Scale Flash MCU HT45F75 Body Fat Scale Flash MCU Crystal Oscillator C1 and C2 Values Crystal Frequency C1 C2 �0MHz 0pF 0pF 1�MHz 0pF 0pF 8MHz 0pF 0pF �MHz 0pF 0pF 1MHz 100pF 100pF Note: C1 and C� values a�e fo� guidan�e only. Crystal Recommended Capacitor Values Internal RC Oscillator – HIRC TheinternalRCoscillatorisafullyintegratedsystemoscillatorrequiringnoexternalcomponents. TheinternalRCoscillatorhasthreefixedfrequenciesofeither4.8MHz,4.8×2MHzor4.8×3MHz. Devicetrimmingduringthemanufacturingprocessandtheinclusionofinternalfrequency compensationcircuitsareusedtoensurethattheinfluenceofthepowersupplyvoltage,temperature andprocessvariationsontheoscillationfrequencyareminimised.Asaresult,atapowersupplyof 5Vandatatemperatureof25°Cdegrees,thefixedoscillationfrequencyof4.8×2MHzwillhave atolerancewithin2%.Notethatifthisinternalsystemclockoptionisselected,asitrequiresno externalpinsforitsoperation,I/OpinsPB1andPB2arefreeforuseasnormalI/Opins. Internal 32kHz Oscillator – LIRC TheInternal32kHzSystemOscillatorisoneofthelowfrequencyoscillatorchoices,whichis selectedviaconfigurationoption.ItisafullyintegratedRCoscillatorwithatypicalfrequencyof 32kHzat5V,requiringnoexternalcomponentsforitsimplementation.Devicetrimmingduring themanufacturingprocessandtheinclusionofinternalfrequencycompensationcircuitsareused toensurethattheinfluenceofthepowersupplyvoltage,temperatureandprocessvariationsonthe oscillationfrequencyareminimised.Asaresult,atapowersupplyof5Vandatatemperatureof 25°Cdegrees,thefixedoscillationfrequencyof32kHzwillhaveatolerancewithin10%. External 32.768kHz Crystal Oscillator – LXT TheExternal32.768kHzCrystalSystemOscillatorisoneofthelowfrequencyoscillatorchoices, whichisselectedviaconfigurationoption.Thisclocksourcehasafixedfrequencyof32.768kHz andrequiresa32.768kHzcrystaltobeconnectedbetweenpinsXT1andXT2.Theexternalresistor andcapacitorcomponentsconnectedtothe32.768kHzcrystalarenecessarytoprovideoscillation. Forapplicationswhereprecisefrequenciesareessential,thesecomponentsmayberequiredto providefrequencycompensationduetodifferentcrystalmanufacturingtolerances.Duringpower-up thereisatimedelayassociatedwiththeLXToscillatorwaitingforittostart-up. WhenthemicrocontrollerenterstheSLEEPorIDLEMode,thesystemclockisswitchedofftostop microcontrolleractivityandtoconservepower.However,inmanymicrocontrollerapplications itmaybenecessarytokeeptheinternaltimersoperationalevenwhenthemicrocontrollerisin theSLEEPorIDLEMode.Todothis,anotherclock,independentofthesystemclock,mustbe provided. However,forsomecrystals,toensureoscillationandaccuratefrequencygeneration,itisnecessary toaddtwosmallvalueexternalcapacitors,C1andC2.TheexactvaluesofC1andC2should beselectedinconsultationwiththecrystalorresonatormanufacturerspecification.Theexternal parallelfeedbackresistor,RP,isrequired. |
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