Isakhiwo singelinye lamakhono omsebenzi ayisisekelo wonjiniyela bokuklama be-PCB. Izinga le-wiring lizothinta ngqo ukusebenza kwalo lonke uhlelo. Iningi lethiyori yedizayini enesivinini esikhulu kufanele ekugcineni isetshenziswe futhi iqinisekiswe ngeSilungiselelo. Kuyabonakala ukuthi i-wiring ibaluleke kakhulu ku ngesivinini PCB umklamo. Okulandelayo kuzohlaziya ukuqonda kwezinye izimo okungenzeka kuhlangatshezwane nazo ekufakeni izintambo kwangempela, futhi kunikeze amanye amasu omzila athuthuke kakhudlwana.

Ichazwa ngokuyinhloko kusukela ezicini ezintathu: izintambo ze-engeli engakwesokudla, izintambo ezihlukanisayo, nezintambo zenyoka.

1. Umzila we-engeli yesokudla

Izintambo ze-engeli yesokudla ngokuvamile ziyisimo esidinga ukugwenywa ngangokunokwenzeka ezintamboni ze-PCB, futhi sekucishe kube ngesinye sezindinganiso zokukala ikhwalithi yezintambo. Ngakho-ke izintambo ze-engeli elungile zizoba nomthelela ongakanani ekudluliselweni kwesignali? Empeleni, umzila we-engeli yesokudla uzoshintsha ububanzi bomugqa wokudlulisela, kubangele ukungaqhubeki ku-impedance. Eqinisweni, hhayi kuphela umzila we-engeli yesokudla, kodwa namakhona kanye nomzila we-acute-engeli kungase kubangele izinguquko zokuthikamezeka.

Umthelela womzila we-engeli yesokudla kusiginali ubonakala kakhulu ezicini ezintathu:

Enye ukuthi ikona lingalingana nomthwalo we-capacitive kulayini wokudlulisa, onciphisa isikhathi sokukhuphuka; okwesibili ukuthi ukungaqhubeki kwe-impedance kuzodala ukubonakaliswa kwesignali; eyesithathu i-EMI ekhiqizwa ithiphu ye-engeli engakwesokudla.

Amandla e-parasitic abangelwa i-engeli elungile yolayini wokudlulisela angabalwa ngefomula yokuhlola elandelayo:

C = 61W (Er) 1/2 / Z0

Kule fomula engenhla, u-C ubhekisela kumandla alinganayo ekhoneni (iyunithi: pF), u-W ubhekisela ebubanzini bokulandelela (iyunithi: iyintshi), u-εr ubhekisela ekungaguquguquki kwe-dielectric kwe-medium, futhi u-Z0 i-impedance eyisici. yolayini wokudlulisela. Isibonelo, kolayini wokudlulisela ongu-4Mils 50 ohm (εr ngu-4.3), amandla alethwa i-engeli elungile cishe ngu-0.0101pF, bese ukushintsha kwesikhathi sokukhuphuka okubangelwa yilokhu kungalinganiselwa:

T10-90%=2.2CZ0/2=2.20.010150/2=0.556ps

Kungabonwa ngokubala ukuthi umphumela we-capacitance olethwa i-trace ye-engeli engakwesokudla mncane kakhulu.

Njengoba ububanzi bomugqa wokulandela umkhondo we-engeli yesokudla bukhula, i-impedance lapho izokwehla, ngakho-ke into ethile yokubonisa isignali izokwenzeka. Singakwazi ukubala i-impedance efanayo ngemva kokwenyuka kobubanzi bomugqa ngokuya ngefomula yokubala yokuvinjelwa okukhulunywe ngayo esahlukweni somugqa wokudlulisela, bese Sibala i-coefficient yokubonisa ngokuya ngefomula ye-empirical:

ρ=(Zs-Z0)/(Zs+Z0)

Ngokuvamile, uguquko lwe-impedance olubangelwa izintambo ze-engeli yesokudla luphakathi kuka-7% -20%, ngakho-ke i-reflection coefficient ephezulu icishe ibe ngu-0.1. Ngaphezu kwalokho, njengoba kungabonakala kumfanekiso ongezansi, ukuvinjelwa komugqa wokudlulisela kushintsha kuya okungenani phakathi nobude bomugqa we-W / 2, bese ubuyela ku-impedance evamile ngemva kwesikhathi se-W/2. Sonke isikhathi sokushintsha kwe-impedance sifushane kakhulu, ngokuvamile singaphakathi kwe-10ps. Ngaphakathi, izinguquko ezinjalo ezisheshayo nezincane cishe azinakwa ekudluliseni isignali evamile.

Abantu abaningi banalokhu kuqonda kwe-wiring ye-right-engeli. Bacabanga ukuthi ithiphu kulula ukuyidlulisela noma ukwamukela amaza kagesi futhi ikhiqize i-EMI. Lokhu kube ngesinye sezizathu ezenza abantu abaningi bacabange ukuthi izintambo ze-right angle azikwazi ukuthuthwa. Kodwa-ke, imiphumela eminingi yokuhlola yangempela ibonisa ukuthi ukulandela ngomkhondo okule kwesokudla ngeke kukhiqize i-EMI esobala kunemigqa eqondile. Mhlawumbe ukusebenza kwethuluzi kwamanje kanye nezinga lokuhlola kukhawulela ukunemba kokuhlolwa, kodwa okungenani kubonisa inkinga. Imisebe yezintambo ezine-engeli engakwesokudla isivele incane kunephutha lokulinganisa lethuluzi ngokwalo.

Ngokuvamile, umzila we-engeli yesokudla akubi ngendlela ocabanga ngayo. Okungenani ezinhlelweni zokusebenza ezingaphansi kwe-GHz, noma yimiphi imiphumela efana namandla, i- reflection, i-EMI, njll. ayibonakali ekuhlolweni kwe-TDR. Onjiniyela bedizayini be-PCB abanesivinini esikhulu kusafanele bagxile ekwakhiweni, ekwakhiweni kwamandla/emhlabathini, nakumklamo wezintambo. Ngezimbobo nezinye izici. Yebo, nakuba umthelela wezintambo ze-engeli engakwesokudla ungewona ubucayi kakhulu, akusho ukuthi sonke singasebenzisa izintambo ze-engeli elungile ngokuzayo. Ukunakwa ngemininingwane yikhwalithi eyisisekelo okufanele wonke unjiniyela omuhle abe nayo. Ngaphezu kwalokho, ngokuthuthukiswa okusheshayo kwamasekhethi edijithali, i-PCB Imvamisa yesiginali ecutshungulwa onjiniyela izoqhubeka nokukhula. Emkhakheni womklamo we-RF ngenhla kwe-10GHz, lawa ma-engeli amancane angakwesokudla angase abe ukugxila kwezinkinga zesivinini esikhulu.

2. Umzila ohlukile

Isiginali ehlukile (i-DifferentialSignal) isetshenziswa kabanzi ekwakhiweni kwesekethe enesivinini esikhulu. Isignali ebaluleke kakhulu kumjikelezo ngokuvamile iklanyelwe ngesakhiwo esihlukile. Yini eyenza idume kangaka? Ungaqinisekisa kanjani ukusebenza kwayo okuhle ekwakhiweni kwe-PCB? Ngale mibuzo emibili, siqhubekela engxenyeni elandelayo yengxoxo.

Iyini isignali ehlukile? Ngokwemigomo ye-layman, isiphetho sokushayela sithumela amasignali amabili alinganayo futhi ahlanekezelwe, futhi isiphetho sokwamukela sahlulela isimo esinengqondo esithi “0” noma “1” ngokuqhathanisa umehluko phakathi kwama-voltage amabili. I-pair of traces ephethe izimpawu ezihlukene ibizwa ngokuthi i-different traces.

Uma kuqhathaniswa nokulandela okujwayelekile kwesignali eyodwa, amasiginali ahlukile anezinzuzo ezisobala kakhulu kulezi zici ezintathu ezilandelayo:

a. Ikhono eliqinile lokulwa nokuphazamiseka, ngoba ukuhlangana phakathi kwemikhondo emibili ehlukene kuhle kakhulu. Uma kukhona ukuphazamiseka komsindo ovela ngaphandle, acishe ahlanganiswe nemigqa emibili ngesikhathi esisodwa, futhi isiphetho sokwamukela sikhathalela kuphela umehluko phakathi kwamasignali amabili. Ngakho-ke, umsindo wemodi evamile yangaphandle ungakhanselwa ngokuphelele. b. Ingacindezela ngempumelelo i-EMI. Ngesizathu esifanayo, ngenxa ye-polarity ephambene yamasignali amabili, amasimu kagesi asakazwa yiwo angakhansela. Lapho ukuhlangana kuqina, amandla kazibuthe amancane angena ezweni langaphandle. c. Ukuma kwesikhathi kunembile. Ngenxa yokuthi ukuguqulwa kweswishi yesiginali yokuhlukanisa kutholakala lapho kuhlangana khona amasiginali amabili, ngokungafani nesignali evamile ene-single-end, encike kuma-voltage aphezulu naphansi ukuze kunqunywe, ayithintwa kancane inqubo kanye nezinga lokushisa, nciphisa iphutha ngesikhathi. , Kodwa futhi kufanelekile kakhulu kumasekhethi wesignali we-amplitude ephansi. I-LVDS edumile yamanje (lowvoltagedifferentialsignaling) ibhekisela kulobu buchwepheshe besignali obuncane be-amplitude.

Konjiniyela be-PCB, okukhathaza kakhulu ukuthi bangaqinisekisa kanjani ukuthi lezi zinzuzo zokuhlukanisa izintambo zingasetshenziswa ngokugcwele kuzintambo zangempela. Mhlawumbe noma ubani oke wathintana ne-Layout uzoqonda izidingo ezijwayelekile zokuhlukanisa izintambo, okungukuthi, “ubude obulinganayo nebanga elilinganayo”. Ubude obulinganayo ukuqinisekisa ukuthi amasignali amabili ahlukene agcina ama-polarity aphikisana ngaso sonke isikhathi futhi anciphise ingxenye yemodi evamile; ibanga elilinganayo ngokuyinhloko liwukuqinisekisa ukuthi ama-impedances ahlukene kokubili ayahambisana futhi anciphisa ukucabangela. “Ngokuseduze ngangokunokwenzeka” ngezinye izikhathi kungenye yezidingo ze-wiring ehlukile. Kodwa yonke le mithetho ayisetshenziselwa ukusebenza ngomshini, futhi onjiniyela abaningi babonakala bengakaqondi ingqikithi yokudluliswa kwesignali ehlukile ngesivinini esikhulu.

Okulandelayo kugxile ekungaqondini okuningana okujwayelekile ekwakhiweni kwesignali ehlukile ye-PCB.

Ukungaqondi kahle 1: Kukholakala ukuthi isignali ehlukile ayidingi indiza ephansi njengendlela ebuyayo, noma ukuthi imikhondo ehlukene inikeza indlela yokubuya komunye nomunye. Isizathu salokhu kungaqondi kahle ukuthi badidwe izenzakalo ezikha phezulu, noma indlela yokudlulisa isignali ngesivinini esiphezulu ayijulile ngokwanele. Kungabonakala esakhiweni sokuphela kokwamukela koMfanekiso 1-8-15 ukuthi ama-emitter currents ama-transistors Q3 ne-Q4 ayalingana futhi aphambene, futhi imisinga yawo ephansi ikhansela ncamashi (I1=0), ngakho-ke Isekhethi ehlukile iwukubhampa okufanayo nezinye izimpawu zomsindo ezingase zibe khona emandleni nasezindizeni eziphansi azinazwelo. Ukukhanselwa kokubuyisela ingxenye yendiza yaphansi akusho ukuthi isifunda esihlukanisayo asisebenzisi indiza yereferensi njengendlela yokubuya kwesignali. Eqinisweni, ekuhlaziyweni kokubuyiselwa kwesignali, indlela yokuhlukanisa izintambo kanye nezintambo ezijwayelekile eziphethwe eyodwa ziyefana, okungukuthi, amasignali amafrikhwensi aphezulu ahlala egeleza kabusha ku-loop nge-inductance encane kakhulu, umehluko omkhulu ukuthi ngaphezu ukuhlangana phansi, umugqa wokuhlukanisa nawo unokuhlangana okuhlangene. Iluphi uhlobo lokuhlanganisa oluqinile, iyiphi eba indlela eyinhloko yokubuya. Umfanekiso 1-8-16 uwumdwebo wohlelo lokusatshalaliswa kwensimu ye-geomagnetic yamasiginali anomkhawulo owodwa namasiginali ahlukene.

Ekwakhiweni kwesekethe ye-PCB, ukuhlangana phakathi kokulandela okuhlukile ngokuvamile kuncane, ngokuvamile kubala kuphela u-10 kuya ku-20% wedigri yokuhlanganisa, futhi okwengeziwe ukuhlangana phansi, ngakho indlela eyinhloko yokubuya yokulandelela okuhlukile isekhona phansi. indiza . Lapho indiza ephansi ingasaqhubeki, ukuhlanganisa phakathi kwemikhondo ehlukene kuzonikeza indlela eyinhloko yokubuya endaweni ngaphandle kwendiza yereferensi, njengoba kuboniswe kuMfanekiso 1-8-17. Nakuba umthelela wokungaqhubeki kwendiza eyinkomba ekulandeleleni okuhlukile ungewona ongathi sína njengalowo womkhondo ojwayelekile ophethe isiphetho esisodwa, usazonciphisa ikhwalithi yesiginali ehlukile futhi ukhulise i-EMI, okufanele igwenywe ngangokunokwenzeka. . Abanye abaklami bakholelwa ukuthi indiza eyinkomba ngaphansi komkhondo ohlukile ingasuswa ukuze kucindezelwe amasiginali wemodi evamile ekudluliseni okuhlukile. Nokho, le ndlela ayifiseleki ngokombono. Indlela yokulawula impedance? Ukungahlinzeki ngeluphu ye-impedance yaphansi yesiginali yemodi evamile kuzodala imisebe ye-EMI nakanjani. Le ndlela yenza umonakalo omkhulu kunokuhle.

Ukungaqondi kahle 2: Kukholakala ukuthi ukugcina isikhala esilinganayo kubaluleke kakhulu kunokufanisa ubude bomugqa. Kusakhiwo sangempela se-PCB, ngokuvamile akwenzeki ukuhlangabezana nezidingo zedizayini ehlukile ngesikhathi esisodwa. Ngenxa yokuba khona kokusatshalaliswa kwephini, i-vias, kanye nesikhala sezintambo, inhloso yokufanisa ubude bomugqa kufanele ifinyelelwe ngokusonteka okufanele, kodwa umphumela kufanele ube ukuthi ezinye izindawo zokubhangqa okuhlukile azikwazi ukuhambisana. Yini okufanele siyenze ngalesi sikhathi? Yikuphi ukukhetha? Ngaphambi kokwenza iziphetho, ake sibheke imiphumela elandelayo yokulingisa.

Kusukela kule miphumela yokulingisa engenhla, kungabonakala ukuthi amagagasi eSkimu 1 kanye neSikimu sesi-2 acishe aqondane, okusho ukuthi, umthelela obangelwa isikhala esingalingani mancane. Uma kuqhathaniswa, umthelela wokungafani kobude bomugqa kusikhathi mkhulu kakhulu. (Isu 3). Kusukela ekuhlaziyweni kwethiyori, nakuba ukuhlukana kwezikhala okungaguquki kuzobangela ukuthi ukuvinjelwa komehluko kushintshe, ngoba ukuhlangana phakathi kwepheya ehlukile ngokwako akubalulekile, uhla lokushintsha kwe-impedance nalo lincane kakhulu, ngokuvamile phakathi kuka-10%, okulingana kuphela nokudlula okukodwa. . Ukucabangela okubangelwa imbobo ngeke kube nomthelela omkhulu ekudlulisweni kwesignali. Uma ubude bomugqa bungahambelani, ngaphezu kwe-offset yesikhathi, izingxenye zemodi evamile zingeniswa kusignali yokuhlukanisa, okunciphisa ikhwalithi yesiginali futhi kwandise i-EMI.

Kungashiwo ukuthi umthetho obaluleke kakhulu ekwakhiweni kokulandela umehluko we-PCB ubude bomugqa ofanayo, futhi eminye imithetho ingaphathwa ngendlela eguquguqukayo ngokuya ngezidingo zokuklama kanye nezicelo ezisebenzayo.

Ukungaqondi kahle 3: Cabanga ukuthi izintambo ezihlukanisayo kumele zibe seduze kakhulu. Ukugcina iminonjana ehlukene iseduze akuyona into engaphezu kokuthuthukisa ukuhlangana kwayo, okungagcini nje ukuthuthukisa ukungatheleleki emsindweni, kodwa futhi kusebenzise ngokugcwele i-polarity ephambene yenkundla kazibuthe ukuze kunqandwe ukuphazamiseka kukazibuthe ezweni langaphandle. Nakuba le ndlela inenzuzo kakhulu ezimweni eziningi, ayiphelele. Uma singaqinisekisa ukuthi zivikelwe ngokugcwele ekuphazamisekeni kwangaphandle, ngakho-ke akudingeki sisebenzise ukuhlanganisa okuqinile ukuze sizuze ukulwa nokuphazamiseka. Futhi inhloso yokucindezela i-EMI. Singakuqinisekisa kanjani ukuhlukaniswa okuhle nokuvikela iminonjana ehlukahlukene? Ukwandisa isikhala ngokunye ukulandelelwa kwesignali kungenye yezindlela eziyisisekelo. Amandla kazibuthe kagesi ancipha ngesikwele sebanga. Ngokuvamile, lapho isikhala somugqa sidlula izikhathi ezi-4 ububanzi bomugqa, ukuphazamiseka phakathi kwawo kuba buthaka kakhulu. Inganakwa. Ngaphezu kwalokho, ukuhlukaniswa yindiza ephansi nakho kungadlala indima enhle yokuvikela. Lesi sakhiwo sivame ukusetshenziswa ekwakhiweni kwe-PCB yephakheji ephezulu (ngaphezulu kwe-10G) ye-IC. Kubizwa ngokuthi yisakhiwo se-CPW, esingaqinisekisa ukungezwani okuqinile komehluko. Ukulawula (2Z0), njengoba kukhonjisiwe kuMfanekiso 1-8-19.

Ukulandela okuhlukile kungaphinda kusebenze ezendlalelo zesignali ezihlukene, kodwa le ndlela ngokuvamile ayinconywa, ngoba umehluko we-impedance kanye ne-vias okukhiqizwa izendlalelo ezihlukene kuzobhubhisa umthelela wokudluliswa kwemodi yokuhlukanisa futhi kwethule umsindo wemodi evamile. Ngaphezu kwalokho, uma izendlalelo ezimbili eziseduze zingahlanganiswa ngokuqinile, kuzonciphisa amandla okulandelana okuhlukile ukumelana nomsindo, kodwa uma ungakwazi ukugcina ibanga elifanele ukusuka emithonjeni ezungezile, i-crosstalk akuyona inkinga. Kumafrikhwensi ajwayelekile (ngezansi kwe-GHz), i-EMI ngeke ibe yinkinga enkulu. Ukuhlola kubonise ukuthi ukuncishiswa kwamandla okukhanya ebangeni elingamamitha angama-500 ukusuka kumkhondo ohlukile sekufinyelele ku-60 dB ebangeni elingamamitha ama-3, okwanele ukuhlangabezana nezinga lemisebe ye-FCC kagesi, ngakho Umklami akudingeki akhathazeke futhi. okuningi mayelana nokungahambisani kukazibuthe okubangelwa ukuhlangana okunganele kolayini ohlukile.

3. Umugqa wenyoka

Ulayini wenyoka wuhlobo lwendlela yomzila evame ukusetshenziswa Kusakhiwo. Inhloso yayo enkulu ukulungisa ukubambezeleka ukuze kuhlangatshezwane nezidingo zedizayini yesikhathi sesistimu. Umklami kufanele aqale abe nalokhu kuqonda: umugqa wenyoka uzobhubhisa ikhwalithi yesignali, uguqule ukubambezeleka kokudlulisela, futhi uzame ukugwema ukuwusebenzisa lapho ufaka izintambo. Kodwa-ke, ekwakhiweni kwangempela, ukuze kuqinisekiswe ukuthi isignali inesikhathi esanele sokubamba, noma ukunciphisa isikhathi sokuvala phakathi kweqembu elifanayo lamasignali, ngokuvamile kuyadingeka ukuvunguza ngamabomu ucingo.

Ngakho-ke, imuphi umphumela ulayini wenyoka enawo ekudluliseleni isignali? Yini okufanele ngiyinake lapho ngifaka izintambo? Amapharamitha amabili abaluleke kakhulu ubude obuhambisanayo bokuhlanganisa (Lp) kanye nebanga lokuhlanganisa (S), njengoba kukhonjisiwe kuMfanekiso 1-8-21. Ngokusobala, lapho isignali idluliselwa kumkhondo wenyoka, izingxenye zomugqa ofanayo zizohlanganiswa ngemodi ehlukile. Incane i-S kanye ne-Lp enkulu, izinga lokuhlangana likhulu. Kungase kubangele ukubambezeleka kokudlulisela kwehliswe, futhi ikhwalithi yesiginali yehliswe kakhulu ngenxa ye-crosstalk. Indlela yokusebenza ingabhekisa ekuhlaziyweni kwemodi evamile kanye ne-crosstalk yemodi yokuhlukanisa eSahlukweni sesi-3.

Okulandelayo ezinye iziphakamiso zonjiniyela be-Layout lapho usebenza nemigqa yenyoka:

1. Zama ukukhulisa ibanga (S) lamasegimenti emigqa ehambisanayo, okungenani enkulu kuno-3H, H ibhekisela ebangeni elisuka kumkhondo wesignali ukuya endizeni eyireferensi. Ngokwabantu abavamile, kuwukuzungeza ijika elikhulu. Inqobo nje uma u-S emkhulu ngokwanele, umphumela wokuhlanganisa ungacishe ugwenywe ngokuphelele. 2. Yehlisa ubude bokuhlanganisa Lp. Uma ukubambezeleka okuphindwe kabili kwe-Lp kusondela noma kudlula isikhathi sokukhuphuka kwesignali, i-crosstalk ekhiqiziwe izofinyelela ekugcwalisweni kwesikhala. 3. Ukubambezeleka kokudluliselwa kwesignali okubangelwa ulayini wenyoka we-Strip-Line noma i-Embedded Micro-strip kungaphansi kwalokho kwe-Micro-strip. Ngokombono, i-stripline ngeke ithinte izinga lokudlulisela ngenxa ye-crosstalk yemodi ehlukile. 4. Ngemigqa yesignali yesivinini esikhulu kanye nalabo abanezidingo eziqinile zesikhathi, zama ukungasebenzisi imigqa yenyoka, ikakhulukazi ezindaweni ezincane. 5. Ungasebenzisa kaningi ukulandelelwa kwenyoka kunoma iyiphi i-engeli, njengesakhiwo se-C ku-Figure 1-8-20, esinganciphisa ngempumelelo ukuhlanganisana. 6. Emklamo we-PCB wesivinini esikhulu, umugqa wenyoka awunakho lokho okubizwa ngokuthi ukuhlunga noma ikhono lokulwa nokuphazamiseka, futhi unganciphisa kuphela ikhwalithi yesignali, ngakho-ke isetshenziselwa ukufanisa isikhathi kuphela futhi ayinayo enye injongo. 7. Kwesinye isikhathi ungacabanga ukuzungeza umzila wokujika. Ukulingisa kukhombisa ukuthi umphumela wako ungcono kunomzila ojwayelekile wenyoka.