Kwiisekethe ze-elektroniki, i-crystal oscillators yenye yezona zinto ziqhelekileyo zewotshi. Ukuqinisekisa ukuqaliswa okufanelekileyo kunye nokusebenza okuzinzile kwe-crystal oscillator, i-capacitors yomthwalo wangaphandle kwisiphaluka kufuneka yenziwe ngokufanelekileyo ngokuhambelana nomthwalo wayo (CL). Ukulinganisa okungafanelekanga kwe-capacitor kunokubangela ubunzima kwi-oscillation, ukunyuka kokuphambuka rhoqo, kunye nokungazinzi kwenkqubo.
Eli nqaku liza kunika uhlalutyo olucacileyo lwentsingiselo ye-crystal oscillator load capacitance, indlela yokubala i-capacitors yangaphandle, kunye neengqwalasela eziphathekayo kuyilo lwesekethe.
Ⅰ. Yintoni i-capacitance yomthwalo (CL) ye-crystal oscillator?
Abavelisi beCrystal bachaza ixabiso le-nominal load capacitance value (CL) kwiphepha ledatha, elifana ne-18pF, 20pF, 12pF, njl njl. Oku kubonisa umthwalo we-capacitive apho ikristale ilinganiswe ukuba iphumeze ukuphindaphinda kwe-oscillation.
Ngamanye amazwi, i-crystal oscillator inokukhupha i-frequency echanekileyo kuphela xa umthamo olinganayo womthwalo ulingana ne-CL.
Ⅱ. Ingaba iiCapacitors zoMlayisho waNgaphandle ziwuchaphazela njani ubungakanani bomthwalo?
Isekethe ye-crystal oscillator eqhelekileyo ithatha le ndlela ilandelayo:
I-C1 kunye ne-C2 zimbini ii-capacitors zangaphandle ezixhunyiwe kumhlaba (ngokuqhelekileyo i-SMD capacitors);
Iiterminal ezimbini ze-XTAL zidibaniswe nezikhonkwane ezimbini ze-crystal oscillator;
Ngokwenza umsebenzi, umthamo olinganayo womthwalo we-CL we-crystal unqunywe yi-C1 kunye ne-C2 kwi-series, idibene ne-parasitic capacitance Cp eyenziwe yi-PCB kunye nephakheji.
Ⅲ. Ifomula yokubala: Limiselwa njani ixabiso leCapacitor yaNgaphandle esekwe kwi-CL?
Ifomyula yomthamo womthwalo olinganayo (CL) imi ngolu hlobo lulandelayo:
Apho:
I-C1, i-C2: Ii-capacitors zangaphandle ezixhunyiwe kumhlaba;
I-Cp: I-Parasitic capacitance eyenziwa yi-PCB traces, ukupakishwa, njl. (ngokuqhelekileyo i-2pF ukuya kwi-5pF, inokuqikelelwa ngokufanisa okanye amava);
I-CL: I-Nominal load capacitance echazwe kwi-crystal oscillator yedatha.
【Umzekelo ongumzekelo】
Cinga ukuba i-crystal specification yi-CL=18 pF, kunye ne-PCB ye-parasitic capacitance Cp ≈ 5pF. Ukubala amaxabiso afanelekileyo e-C1 kunye ne-C2:
Okokuqala, faka amaxabiso endaweni yefomula:
Ukuthatha C1=C2=C, ifomula yenza lula uku:
Isiphumo sithi:
✅ Ke ngoko, ii-capacitors zangaphandle ezicetyiswayo zezi: C1=C2 =27pF (Ixabiso eliMgangatho).
Ⅳ. Kutheni le nto iiCapacitors zaNgaphandle ezingahambelaniyo zibangela iingxaki?
Ukutenxa rhoqo: Ukuba i-capacitors yangaphandle incinci kakhulu okanye inkulu kakhulu, i-crystal iya kuphambuka kwi-frequency yayo ebizwa ngokuba yi-frequency frequency, ibangela iimpazamo zewashi.
Qalisa-ubunzima okanye ukungazinzi: Ukulayisha ngokugqithisileyo kunciphisa inzuzo, nto leyo enokubangela ukuba ikristale isilele ukuqalisa okanye ukufumana i-jitter frequency.
Ukusetyenziswa kwamandla okunyuka: Ukulayisha okungafanelekanga kukhokelela ekusebenziseni amandla aphezulu kwi-crystal oscillator circuit.
Ukonyuka kwe-EMI: Ii-oscillations ezingazinzanga zinokuvelisa amaza abubuxoki, achaphazela inkqubo yokuhambelana kwe-electromagnetic (EMC).
Ⅴ. Iingcebiso zoYilo kunye neZenzo zobuNjineli
Hlola ngokucophelela i-crystal oscillator yedatha
Qinisekisa ixabiso le-CL.
Qonda itopology yesekethe ecetyiswayo.
Khangela ukuba uluhlu lwamaxabiso e-capacitor yangaphandle luyacetyiswa.
2. Qwalasela eyona ndawo yebhodi
Qikelela i-Cp usebenzisa ukulinganisa kwe-PCB okanye amava.
Kwi-isantya esiphezulu okanye iiwotshi ezichanekileyo (umzekelo, iinkqubo zonxibelelwano, i-MCU main frequency > 100MHz), ukubala okuchanekileyo okanye uvavanyo luyacetyiswa.
3. Sebenzisa i-symmetrical capacitors
Kuyacetyiswa ngokubanzi ukuba i-C{0}} C2 ibeke iziko lokuphindaphinda kunye nengxolo elinganayo.
Uyilo lwe-asymmetrical lungasetyenziselwa iimfuno ezikhethekileyo zokufanisa.
4. Sebenzisa uluhlu lwe-SMD capacitor ukulungisa ingxaki
Zama nge-SMD capacitors (umzekelo, i-10pF, i-15pF, i-22pF, i-27pF, njl.) ukufumana ukulingana okufanelekileyo;
Jonga ukuzinza kwemveliso kunye nokuchaneka rhoqo usebenzisa i-spectrum analyzer okanye i-oscilloscope.
6,EqhelekileyoFAQ
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Imibuzo |
Iimpendulo |
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Ukuba i-CL=12 pF, leliphi ixabiso kufuneka libe yi-capacitors yangaphandle? |
Ukuba Cp=5pF, ngoko C1=C2≈14pF |
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Kutheni ezinye ii-MCUs zingadingi ii-capacitors zangaphandle? |
Ezinye iisekethi zecrystal oscillator zakhelwe-kwi-capacitor yomthwalo (umzekelo, STM32), ngoko ke akukho zikhampasi zangaphandle zifunekayo. |
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Ngaba i-capacitors yangaphandle engahambelaniyo inokuyonakalisa i-crystal oscillator? |
Ngokuqhelekileyo, abayi kuyitshisa okanye bayonakalise, kodwa banokubangela ukusilela kokuqalisa okanye iimpazamo eziphindaphindiweyo. |
Ukuqukumbela
Uyilo lwee-capacitors zangaphandle zomthwalo we-crystal oscillator yinkcukacha encinci kodwa ebalulekileyo echaphazela ngokuthe ngqo ukuzinza kunye nokuchaneka kwenkqubo yewashi. Ukuqonda ubudlelwane bokubala phakathi kwe-CL kunye ne-C1 / C2, kunye nokulungelelanisa iiparitha ezisekelwe kwi-PCB yangempela ye-parasitic capacitance, ngundoqo ekufezekiseni i-oscillation ethembekileyo kunye ne-frequency frequency.
Kwisantya esiphezulu-inkqubo yedijithali, izixhobo zonxibelelwano, okanye iisistim ezinemfuno zewotshi ezibalela kakhulu, ukukhetha ngokufanelekileyo nokuthelekisa umthamo womthwalo wecrystal oscillator ngumsebenzi wobunjineli omawuthathelwe ingqalelo.
HCIinelabhoratri yobuchwephesha kunye neqela leenjineli zezicelo ezineminyaka engaphezu kwama-20 yamava, zibonelela ngeenkonzo zasimahla zokuthelekisa kunye novavanyo kubathengi. Ukuba unayo naziphi na iimfuno kulo mba, nceda uzive ukhululekile ukuqhagamshelana neentengiso zethu okanye abasebenzi bezobugcisa.