A cikin da'irori na lantarki, kristal oscillators suna ɗaya daga cikin mafi yawan tushen agogo. Don tabbatar da farawa mai kyau da kwanciyar hankali na oscillator kristal, dole ne a tsara masu ƙarfin ɗaukar nauyi na waje a cikin da'irar daidai gwargwadon ƙarfin ƙarfinsa (CL). Daidaitaccen madaidaicin capacitor na iya haifar da wahala a cikin oscillation, ƙara yawan karkatar da mitar, har ma da rashin kwanciyar hankali na tsarin.
Wannan labarin zai ba da cikakken bayani game da ma'anar ƙarfin ɗaukar nauyi na crystal oscillator, hanyar ƙididdigewa don masu ƙarfin waje, da la'akari masu amfani a cikin ƙirar kewaye.
Ⅰ. Menene ƙarfin ɗaukar nauyi (CL) na oscillator crystal?
Crystal masana'antun yawanci saka da maras muhimmanci load capacitance darajar (CL) a cikin datasheet, kamar 18pF, 20pF, 12pF, da dai sauransu. Wannan yana wakiltar capacitive load karkashin abin da crystal aka calibrated don cimma maras muhimmanci oscillation mita.
A wasu kalmomi, kristal oscillator na iya fitar da madaidaicin mitar kawai lokacin da madaidaicin ƙarfin nauyi yayi daidai da CL.
Ⅱ. Ta yaya Capacitors na Load na waje ke shafar ƙarfin Load?
Da'irar oscillator crystal na al'ada yana ɗaukar nau'i mai zuwa:
C1 da C2 sune capacitors na waje guda biyu da aka haɗa zuwa ƙasa (yawanci masu ƙarfin SMD);
An haɗa tashoshi biyu na XTAL zuwa fil biyu na oscillator crystal;
A aikace, madaidaicin ƙarfin ƙarfin CL na crystal an ƙaddara ta C1 da C2 a cikin jerin, haɗe tare da ƙarfin ƙarfin parasitic Cp da PCB da kunshin suka gabatar.
Ⅲ. Ƙididdigar Ƙididdigar: Yadda za a Ƙayyade Ƙimar Capacitor Na waje bisa CL?
Ƙididdigar ma'auni na daidaitattun ƙarfin nauyi (CL) shine kamar haka:
Inda:
C1, C2: Na'urorin haɗi na waje da aka haɗa zuwa ƙasa;
Cp: Ƙaƙƙarfan ƙarfin da aka gabatar ta hanyar PCB, marufi, da dai sauransu (yawanci 2pF zuwa 5pF, ana iya kiyasta ta hanyar kwaikwayo ko kwarewa);
CL: Ƙaƙƙarfan ƙayyadaddun ƙimar ƙima da aka ƙayyade a cikin bayanan oscillator crystal.
【Misalin Misali】
A ɗauka ƙayyadaddun ƙayyadaddun crystal shine CL=18pF, da kuma PCB parasitic capacitance Cp ≈ 5pF. Don lissafta ma'auni masu dacewa don C1 da C2:
Da farko, musanya dabi'u cikin dabara:
Dauka C 1=C 2=C, dabarar ta sauƙaƙa zuwa:
Sakamakon shine:
✅ Saboda haka, shawarar waje capacitors shine: C1=C2 =27pf ku (Standard Value).
Ⅳ. Me yasa Matsalolin Wutar Lantarki Ba Su Daidaita Ba Ke haifar da Matsaloli?
Sabanin mitoci: Idan capacitors na waje sun yi ƙanƙanta ko girma sosai, kristal zai karkata daga mitar sa, yana haifar da kurakuran agogon tsarin.
Fara -wahala ko rashin zaman lafiya: Yin lodi mai yawa yana rage riba, wanda zai iya sa kristal ya kasa farawa ko kuma fuskantar tashin hankali.
Ƙarfafa amfani da wutar lantarki: Rashin yin lodi mara kyau yana haifar da yawan amfani da makamashi a cikin da'irar oscillator crystal.
Ƙara EMI: Ƙaƙƙarfan jujjuyawa na iya haifar da mitoci masu banƙyama, suna shafar daidaitawar tsarin lantarki (EMC).
Ⅴ. Shawarwari Zane da Ayyukan Injiniya
A hankali bitar bayanan bayanan oscillator crystal
Ƙayyade ƙimar CL.
Fahimtar da'irar da'ira da aka ba da shawarar.
Bincika idan ana ba da shawarar kewayon kimar capacitor na waje.
2. Yi la'akari da ainihin yanayin hukumar
Ƙididdiga Cp ta amfani da simintin PCB ko ƙwarewa.
Don manyan agogo ko daidaitattun agogo (misali, tsarin sadarwa, babban mitar MCU> 100MHz), ana ba da shawarar ƙididdiga ko gwaji.
3. Yi amfani da capacitors na simmetric
Ana ba da shawarar cewa C{0}} C2 don daidaita mita da ma'auni amo.
Hakanan ana iya amfani da ƙirar asymmetrical don buƙatun dacewa na musamman.
4. Yi amfani da jeri na capacitor na SMD don gyara kuskure
Gwaji tare da capacitors SMD (misali, 10pF, 15pF, 22pF, 27pF, da sauransu) don nemo dacewa mai dacewa;
Bincika daidaiton fitarwa da daidaiton mita ta amfani da na'urar nazarin bakan ko oscilloscope.
6,Na kowaFAQ
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Tambayoyi |
Amsa |
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Idan CL=12pF, wace ƙimar ya kamata masu ƙarfin waje su kasance? |
Idan Cp =5pF, sannan C1=C2≈14pF |
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Me yasa wasu MCUs basa buƙatar capacitors na waje? |
Wasu da'irori na oscillator crystal sun gina{0} a cikin ma'ajin masu ɗaukar nauyi (misali, STM32), don haka ba a buƙatar masu ƙarfin waje. |
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Shin na'urorin da ba su dace ba na waje suna iya lalata oscillator crystal? |
Yawanci, ba za su ƙone ko lalata shi ba, amma suna iya haifar da gazawar farawa ko kurakurai na mitoci. |
Kammalawa
Zane-zanen masu ƙarfin ɗaukar nauyi na waje don oscillator kristal ƙarami ne amma mai mahimmanci daki-daki wanda ke shafar daidaito da daidaiton tsarin agogo kai tsaye. Fahimtar dangantakar lissafi tsakanin CL da C1/C2, da daidaita ma'auni dangane da ainihin ƙarfin PCB parasitic capacitance, shine mabuɗin don cimma amintaccen oscillation da madaidaiciyar mita.
A cikin babban tsarin dijital-, kayan sadarwa, ko tsarin tare da buƙatun agogo mai matuƙar buƙata, zaɓi da kyau da daidaita ƙarfin lodin oscillator aikin injiniyan da dole ne a ɗauke shi da mahimmanci.
HCIyana da dakin gwaje-gwaje na ƙwararru da ƙungiyar injiniyoyin aikace-aikacen tare da gogewar shekaru sama da 20, suna ba da ƙwararrun ƙwararrun matching da sabis na gwaji kyauta ga abokan ciniki. Idan kuna da wasu buƙatu a wannan batun, don Allah ku ji daɗi don tuntuɓar tallace-tallacenmu ko ma'aikatan fasaha.