Ukunemba kwama-Crystal Oscillator: Lisho Ukuthini Iphutha Le-1ppm?
Esikhathini esinembayo nemishini kagesi ehlukahlukene, ama-crystal oscillator asebenza njengemithombo yewashi eyinhloko, futhi ukuzinza kwawo kwemvamisa kunquma ngokuqondile ukunemba kwesikhathi kwesistimu. Kodwa-ke, ekusebenzeni okusebenzayo, ama-crystal oscillator awazona izingxenye ezifanelekile; imvamisa yokuphuma kwabo ingaphambuka ngenxa yezici ezihlukahlukene. Lesi sihloko sizocubungula ukuqonda iyunithi yephutha lemvamisa ppm futhi iyiguqule ibe ukuchezuka okuqondakala kalula kwansuku zonke.
ppm (izingxenye ngesigidi) iyunithi evamile yokulinganisa ukuchezuka kwefrikhwensi ehlobene. Iphutha elingu-1ppm libonisa ukuthi ukuchezuka phakathi kwefrikhwensi yangempela kanye nemvamisa yegama yingxenye eyodwa ngesigidi.
Ukubala ukuchezuka kwesikhathi esiqongelelwe ngosuku olulodwa kuqondile:
Isamba samasekhondi ngosuku: amahora angu-24 × amaminithi angu-60 × amasekhondi angu-60=86, amasekhondi angu-400.
Isibalo sokuchezuka: Iphutha le-1ppm lisho ukuthi njalo ngesekhondi elingu-1,000,000, kuba khona ukuchezuka kwesekhondi elingu-1. Ngakho-ke, ukuchezuka ngaphezu kwamasekhondi angu-86,400 ukuthi:
Isikhathi sokuchezuka=(1 / 1,000,000) × 86,400 amasekhondi=0.0864 amasekhondi
Lokhu kusho ukuthi i-crystal oscillator +1nephutha lefrikhwensi ye-ppm izothola cishe amasekhondi angu-0.0864 (cishe 86.4 ama-millisecond) ngosuku. Lesi sibalo sisebenza emhlabeni wonke futhi asizimele kubuningi bekristalu ethile (njengejwayelekile engu-32.768kHz) ngoba sisekelwe kumgomo wephutha elihlobene. Ngokufanayo, iphutha -1ppm lisho ukulahlekelwa imizuzwana engu-0.0864 ngosuku.
Izinto Eziyinhloko Ezithinta Ukuzinza Kwemvamisa Nezinyathelo Zokulwa
Ekusetshenzisweni okungokoqobo, ukufeza isikhathi esinembile, kubalulekile ukuqonda nokuphatha izici ezihlukahlukene ezithinta ukuzinza kwama-crystal oscillator.
1. Izinga Lokushisa Lemvelo
Umthelela: Ukushintsha kwezinga lokushisa kuyisici esiyinhloko esidala ukukhukhuleka kwamakristalu. I-resonant frequency ye-crystal iyahlukahluka nezinga lokushisa ku-cubic curve.
I-Countermeasure:Kuzinhlelo zokusebenza ezinokwehluka okuphawulekayo kwezinga lokushisa, izinga lokushisa{0}}ama-crystal oscillator (TCXO) kufanele asetshenziswe; ngezidingo eziphakeme kakhulu-zokunemba, kuhhavini{2}}ama-crystal oscillator alawulwayo (OCXO) ayadingeka, abeka ikristalu kuhhavini wamazinga okushisa angaguquki ukuze kuqedwe imiphumela yokushisa.
2. Ukufanisa Ikhono Lomthwalo
Umthelela: Izikhonkwane ezimbili ze-crystal oscillator zidinga ukuxhunywa kuma-capacitor okulayisha afanelekile (CL) ukuze asebenze kumaza okuvamile. Amanani angalungile we-capacitance angabangela ngokuqondile ukuchezuka kwefrikhwensi.
Isilinganiso Sokumelana: Khetha ngokuqinile ama-capacitor angaphandle afanayo ngokusekelwe kumanani omthamo womthwalo anconyiwe kumininingwane yedatha yekristalu, futhi ucabangele amandla e-parasitic kusakhiwo se-PCB.
3. I-Voltage Yokuhlinzeka Amandla
Umthelela: Ukushintshashintsha kwe-voltage yokusebenza kungashintsha kancane izici ze-oscillator, ngaleyo ndlela kuthinte imvamisa yokuphumayo.
I-Countermeasure:Nikeza ngokuhlinzeka kwamandla kagesi ahlanzekile futhi azinzile wesekethe ye-oscillator, ngokuvamile esebenzisa i-LDO ({0}}isilawuli sokuyeka) kanye nokuhlukanisa okwanele.
4. Ukuguga Umphumela
Umthelela:Ekusetshenzisweni-kwesikhathi eside, ikristalu nezinto zayo zihamba kancane, i-unidirectional frequency drift (imvamisa ibe yinhle) ngenxa yokukhululeka kwengcindezi yangaphakathi, ukuhwamuka kwezinto, njll.
I-Countermeasure: Khetha imikhiqizo yekristalu enamazinga aphansi okuguga. Kumasistimu adinga{1}}ukusebenza kwesikhathi eside, klama imisebenzi yokulinganisa iwashi ngezikhathi ezithile okuzenzakalelayo noma okwenziwa ngesandla.
5. Ukugxambukela Kwangaphandle
Umthelela:I-electromagnetic interference (EMI) ebhodini lesekhethi, kanye nokudlidliza komshini nokushaqeka, kungabangela-ukungaqini kwefrikhwensi yesikhathi esifushane.
Isilinganiso:Isakhiwo se-PCB esihle (njengokumisa phansi nxazonke zewashi), ukusetshenziswa kwamathini okuvikela, nokukhetha amaphakheji ekristalu anokumelana nokudlidliza okungcono (njengamaphakheji ensimbi) kuyizixazululo ezisebenzayo.
Isifinyezo
Kafushane, iphutha le-1ppm ku-crystal oscillator lihumusha ngokuqondile ukuchezuka kwesikhathi sansuku zonke cishe kwemizuzwana engu-0.0864. Lapho ukhetha futhi uklama amasekhethi wewashi, kuyadingeka ukulinganisa izindleko nokusebenza ngokusekelwe ezindingweni zokunemba zohlelo lokusebenza (njengogesi ojwayelekile wabathengi, amawashi ahlakaniphile, iziteshi eziyisisekelo zokuxhumana, noma amasistimu wokuzulazula), khetha izinhlobo ezifanele ze-oscillator (isb, i-SPXO, i-TCXO, i-OCXO), futhi usebenzise izinyathelo ezihambisanayo zokuklama ukuzinza. Ukuqonda le mithombo yamaphutha nezinyathelo zokuphikisa kuyisihluthulelo sokuqinisekisa isikhathi esithembekile nesinembile kumishini kagesi.