Ubale Pakati pa Ma Capacitor Onyamula Zakunja ndi Crystal Load

M'mabwalo apakompyuta, ma oscillator a crystal ndi amodzi mwa mawotchi omwe amapezeka kwambiri. Kuti zitsimikizire kuyambika koyenera komanso kugwira ntchito mokhazikika kwa kristalo oscillator, ma capacitor onyamula katundu akunja amayenera kupangidwa bwino molingana ndi mphamvu yake yonyamula katundu (CL). Kufananiza kosayenera kwa capacitor kungayambitse kuvutikira kwa oscillation, kuwonjezereka kwapang'onopang'ono, komanso kusakhazikika kwadongosolo.

Nkhaniyi ifotokoza mwatsatanetsatane tanthauzo la crystal oscillator load capacitance, njira yowerengera ma capacitor akunja, ndi malingaliro othandiza pakupanga dera.

Ⅰ. Kodi capacitance (CL) ya crystal oscillator ndi chiyani?

Opanga ma Crystal nthawi zambiri amatchula kuchuluka kwa mphamvu ya kristalo (CL) mu datasheet, monga 18pF, 20pF, 12pF, ndi zina zotero. Izi zimayimira capacitive load yomwe krustalo imawunikiridwa kuti ikwaniritse ma frequency ake.

Mwanjira ina, oscillator wa kristalo amatha kutulutsa ma frequency olondola pokhapokha mphamvu yofanana ndi yofanana ndi CL.

Ⅱ. Kodi Ma Capacitor Akunja Amakhudza Bwanji Katundu Wonyamula?

Mawonekedwe a crystal oscillator amatenga mawonekedwe awa:

C1 ndi C2 ndi ma capacitor awiri akunja olumikizidwa pansi (makamaka SMD capacitors);

Ma terminal awiri a XTAL amalumikizidwa ndi zikhomo ziwiri za crystal oscillator;

Pochita, wofanana katundu capacitance CL wa kristalo anatsimikiza ndi C1 ndi C2 mndandanda, pamodzi ndi parasitic capacitance Cp anayambitsa ndi PCB ndi phukusi.

Ⅲ. Fomula Yowerengera: Momwe Mungadziwire Mtengo wa Capacitor Wakunja Kutengera CL?

Fomula ya mphamvu yofanana ya katundu (CL) ndi motere:

Kumene:

C1, C2: Ma capacitor akunja olumikizidwa pansi;

Cp: ​​Mphamvu ya Parasitic yomwe imayambitsidwa ndi zizindikiro za PCB, kuyika, ndi zina (nthawi zambiri 2pF mpaka 5pF, ikhoza kuwerengedwa kupyolera mu kuyerekezera kapena zochitika);

CL: Mphamvu yodziwika bwino yotchulidwa mu crystal oscillator datasheet.

【Chitsanzo Chachifanizo】

Tangoganizani kuti mawonekedwe a galasi ndi CL=18pF, ndi PCB parasitic capacitance Cp ≈ 5pF. Kuwerengera mitengo yoyenera ya C1 ndi C2:

Choyamba, sinthani ma values ​​mu fomula:

Kungotengera C1=C2=C, ndondomekoyi imapangitsa kuti:

Zotsatira zake ndi:

✅ Choncho, ma capacitor akunja ovomerezeka ndi awa: C1=C2 =27pf pa (Kufunika Kwambiri).

Ⅳ. Chifukwa Chiyani Ma Capacitor Akunja Osagwirizana Amayambitsa Mavuto?

Kupatuka kwapang'onopang'ono: Ngati ma capacitor akunja ndi ang'onoang'ono kapena akulu kwambiri, kristaloyo imachoka pamafupipafupi ake, zomwe zimayambitsa zolakwika za wotchi.

Yambani-zovuta kapena kusakhazikika: Kutsegula kwambiri kumachepetsa kupindula, zomwe zingapangitse crystal kulephera kuyambitsa kapena kukumana ndi jitter pafupipafupi.

Kuchulukitsa kwamphamvu kwamagetsi: Kutsegula molakwika kumabweretsa kugwiritsa ntchito mphamvu kwambiri mudera la crystal oscillator.

Kuchulukitsa kwa EMI: Ma oscillation osakhazikika amatha kupanga ma frequency olakwika, omwe amakhudza kutengera kwamagetsi amagetsi (EMC).

Ⅴ. Zopangira Zopangira ndi Zochita Zaumisiri

Yang'anani mosamala za crystal oscillator

Dziwani mtengo wa CL.

Mvetserani mayendedwe ovomerezeka a dera.

Onani ngati mitundu yosiyanasiyana ya ma capacitor akunja ndiyofunikira.

2. Ganizirani malo enieni a bolodi

Yerekezerani Cp pogwiritsa ntchito kayeseleledwe ka PCB kapena zinachitikira.

Pamawotchi othamanga kwambiri kapena olondola (monga makina olumikizirana, mafupipafupi a MCU > 100MHz), kuwerengetsa kapena kuyezetsa kolondola ndi kovomerezeka.

3. Gwiritsani ntchito ma symmetrical capacitors

Nthawi zambiri tikulimbikitsidwa kuti C1=C2 ikhazikike pakati pa ma frequency ndi kusanja phokoso.

Mapangidwe aasymmetric angagwiritsidwenso ntchito pazofunikira zapadera zofananira.

4. Gwiritsani ntchito gulu la SMD capacitor kuti mukonze zolakwika

Yesani ndi ma capacitor a SMD (mwachitsanzo, 10pF, 15pF, 22pF, 27pF, etc.) kuti mupeze zoyenera;

Yang'anani kukhazikika kotulutsa ndi kulondola pafupipafupi pogwiritsa ntchito spectrum analyzer kapena oscilloscope.

6,WambaFAQ

Mapeto

Mapangidwe a kunja kwa katundu capacitor kwa crystal oscillator ndi mfundo yaing'ono koma yovuta yomwe imakhudza mwachindunji kukhazikika ndi kulondola kwa dongosolo la wotchi. Kumvetsetsa mgwirizano wa mawerengedwe pakati pa CL ndi C1 / C2, ndi kusintha magawo kutengera mphamvu yeniyeni ya PCB ya parasitic capacitance, ndikofunikira kuti tikwaniritse oscillation yodalirika komanso pafupipafupi.

M'makina-othamanga kwambiri a digito, zida zoyankhulirana, kapena makina ofunikira kwambiri mawotchi, kusankha bwino ndi kufananiza kuchuluka kwa crystal oscillator's load capacitance ndi ntchito yaumisiri yomwe iyenera kuonedwa mozama.

HCIili ndi labotale yaukadaulo komanso gulu la mainjiniya ogwiritsira ntchito azaka zopitilira 20, omwe amapereka ntchito zaulere zofananira ndi kuyesa kwa makasitomala. Ngati muli ndi zosowa pankhaniyi, chonde omasuka kulumikizana ndi ogulitsa kapena ogwira ntchito zaukadaulo.