Na sekit eletrọnịkị, oscillator kristal bụ otu n'ime isi mmalite elekere. Iji hụ na mmalite kwesịrị ekwesị na ịrụ ọrụ kwụsiri ike nke oscillator kristal, a ga-emerịrị ndị na-ebu ibu dị na sekit nke ọma dịka ike ibu ya (CL). Nkwekọrịta capacitor na-ezighi ezi nwere ike ịkpata ihe isi ike na oscillation, mmụba ugboro ugboro, na ọbụna enweghị ntụkwasị obi sistemụ.
Isiokwu a ga-enye nkọwa zuru ezu nke nkọwa nke kristal oscillator load capacitance, usoro mgbako maka mpụga capacitors, na echiche bara uru na imewe sekit.
Ⅰ. Gịnị bụ ibu capacitance (CL) nke kristal oscillator?
Ndị na-emepụta kristal na-akọwakarị uru ikike ibu arọ (CL) na mpempe akwụkwọ data ahụ, dịka 18pF, 20pF, 12pF, wdg.
N'ikwu ya n'ụzọ ọzọ, oscillator kristal nwere ike iwepụta oge ziri ezi naanị mgbe ikike nha nha nha nhata CL.
Ⅱ. Kedu ka Capacitors Ibu Mpụga si emetụta ike ibu?
Otu sekit oscillator kristal na-ewere ụdị a:
C1 na C2 bụ abụọ mpụga capacitors ejikọrọ na ala (na-emekarị SMD capacitors);
A na-ejikọta ọnụ abụọ nke XTAL na ntụtụ abụọ nke oscillator kristal;
Na omume, a na-ekpebi ikike nha nha CL nke kristal site na C1 na C2 n'usoro, jikọtara ya na ikike parasitic Cp webatara site na PCB na ngwugwu.
Ⅲ. Usoro Mgbakọ: Otu esi achọpụta uru Capacitor Mpụga dabere na CL?
Usoro maka ikike ibu nha nha (CL) bụ nke a:
Ebe:
C1, C2: Mpụga capacitors ejikọrọ na ala;
Cp: Ike parasitic ewepụtara site na PCB trace, nkwakọ ngwaahịa, wdg (na-abụkarị 2pF ruo 5pF, enwere ike ime atụmatụ site na ịme anwansị ma ọ bụ ahụmịhe);
CL: ikike ibu ọnụ nke akọwapụtara na mpempe akwụkwọ data oscillator kristal.
【Ihe Nlereanya】
Were ya na nkọwapụta kristal bụ CL=18pF, yana PCB parasitic capacitance Cp ≈ 5pF. Iji gbakọọ ụkpụrụ kwesịrị ekwesị maka C1 na C2:
Nke mbụ, dochie ụkpụrụ n'ime usoro:
Na-eche na C1=C2=C, usoro a na-adị mfe:
Nsonaazụ bụ:
✅ Ya mere, ndị na-akwado mpụga capacitors bụ: C1=C2 =27pF (Standard Uru).
Ⅳ. Kedu ihe kpatara na Capacitors mpụga na-adaghị adaba na-akpata nsogbu?
Ntugharị ugboro ugboro: Ọ bụrụ na ndị ikike mpụga dị obere ma ọ bụ buru oke ibu, kristal ga-esi na ugboro ole aha ya pụta, na-ebute njehie elekere sistemụ.
Bido - isi ike ma ọ bụ enweghị ntụkwasị obi: ibu oke ibu na-ebelata uru, nke nwere ike ime ka kristal ghara ịmalite ma ọ bụ nwee ahụmịhe ugboro ole.
Enwekwu ike oriri: Ịkwado na-ezighị ezi na-eduga n'inwe ike dị elu na sekit oscillator kristal.
Mmụba EMI: Oscillations na-adịghị akwụsi ike nwere ike iwepụta frequencies dị egwu, na-emetụta ndakọrịta elektrọnịkị sistemu (EMC).
Ⅴ Ntụnye atụmatụ na mmemme injinia
Jiri nlezianya nyochaa mpempe akwụkwọ data oscillator kristal
Kpebie uru CL.
Ghọta topology sekit akwadoro.
Lelee ma ọ bụrụ na akwadoro oke nke ụkpụrụ capacitor mpụga.
2. Tụlee gburugburu ebe obibi osisi
Tụlee Cp site na iji simulation PCB ma ọ bụ ahụmịhe.
Maka nnukwu - elekere ma ọ bụ nkenke (dịka ọmụmaatụ, sistemu nkwukọrịta, ugboro ugboro MCU> 100MHz), a na-atụ aro mgbako ma ọ bụ nnwale.
3. Jiri symmetrical capacitors
A na-atụkarị aro ka C{0}} C2 ka ọ bụrụ n'etiti ugboro na nguzozi mkpọtụ.
A nwekwara ike iji nhazi asymmetrical maka ihe ndị chọrọ dakọtara pụrụ iche.
4. Jiri array capacitor SMD maka nbipu
Nnwale na ndị na-emepụta SMD (dịka, 10pF, 15pF, 22pF, 27pF, wdg) iji chọta nke dabara adaba;
Lelee nkwụsi ike mmepụta yana izi ezi ugboro site na iji ihe nyocha spectrum ma ọ bụ oscilloscope.
6,A na-ahụkarịFAQ
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Ajụjụ |
Azịza ya |
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Ọ bụrụ CL=12pF, kedu uru mpụta capacitors kwesịrị ịbụ? |
Ọ bụrụ Cp =5pF, wee C1=C2≈14pF |
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Kedu ihe kpatara na ụfọdụ MCU anaghị achọ capacitors mpụga? |
Ụfọdụ sekit oscillator kristal arụwo - n'ime ike ibu (dịka ọmụmaatụ, STM32), yabụ na ọ nweghị ihe ike mpụga achọrọ. |
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Ndị na-emepụta ihe na-abụghị nke mpụga nwere ike imebi oscillator kristal? |
Na-emekarị, ha agaghị agba ọkụ ma ọ bụ mebie ya, mana ha nwere ike ibute ọdịda mmalite ma ọ bụ mperi ugboro ole. |
Mmechi
Nhazi nke capacitors ibu mpụga maka oscillator kristal bụ obere nkọwa dị oke egwu nke na-emetụta nkwụsi ike na izi ezi nke usoro elekere ozugbo. Ịghọta mmekọrịta ngụkọ dị n'etiti CL na C1/C2, na ịhazigharị paramita dabere na ike PCB parasitic capacitance n'ezie, bụ isi ihe iji nweta oscillation a pụrụ ịdabere na ya na oge ziri ezi.
N'ime usoro dijitalụ ọsọ ọsọ{{0}, ngwa nzikọrịta ozi, ma ọ bụ sistemu nwere oke elekere chọrọ, ịhọpụta nke ọma yana kwekọọ ikike ibu kristal oscillator bụ ọrụ injinia nke a ga-ejirịrị kpọrọ ihe.
HCInwere ụlọ nyocha ọkachamara na otu ndị injinia ngwa nwere ahụmịhe karịrị afọ 20, na-enye ndị ahịa ọrụ egwuregwu na nnwale n'efu. Ọ bụrụ na ị nwere mkpa ọ bụla na nke a, biko nweere onwe gị ịkpọtụrụ ndị ahịa anyị ma ọ bụ ndị ọrụ teknụzụ.