Uyilo sesinye sezona zakhono zisisiseko zomsebenzi kwiinjineli zoyilo zePCB. Umgangatho we-wiring uya kuchaphazela ngokuthe ngqo ukusebenza kwenkqubo yonke. Uninzi lweethiyori zoyilo olukwisantya esiphezulu kufuneka ziphunyezwe ekugqibeleni kwaye zingqinwe ngoYilo. Kuya kubonakala ukuba i-wiring ibaluleke kakhulu kwi Isantya esiphezulu sePCB uyilo. Oku kulandelayo kuya kuhlalutya ingqiqo kwezinye iimeko ekunokuthi kuhlangatyezwane nazo kwiingcingo zokwenyani, kwaye zinike ezinye iindlela zobuchule eziphuculweyo.

Icaciswa ikakhulu kwimiba emithathu: i-engile-engile yocingo, i-wiring yokwahlukana, kunye ne-serpentine wiring.

1. Indlela ye-engile yasekunene

Iingcingo zasekunene-engile ngokuqhelekileyo yimeko ekufuneka iphetshwe kangangoko kunokwenzeka kwi-PCB yocingo, kwaye iphantse yaba ngomnye wemigangatho yokulinganisa umgangatho wocingo. Ke ingaba ingakanani impembelelo i-wiring ye-engile ekunene ekuhanjisweni komqondiso? Ngokomgaqo, umzila we-angle-engile uya kutshintsha ububanzi bomgca womzila wothumelo, obangela ukupheliswa kwe-impedance. Ngapha koko, hayi indlela ye-engile ekunene kuphela, kodwa kunye neekona kunye ne-acute-angle yomzila inokubangela utshintsho lwe-impedance.

Impembelelo ye-engile ekunene kwindlela yomqondiso ibonakala ikakhulu kwimiba emithathu:

Enye kukuba ikona inokulingana nomthwalo we-capacitive kumgca wokuhambisa, onciphisa ixesha lokunyuka; okwesibini kukuba ukungaqhubeki kwe-impedance kuya kubangela ukubonakaliswa komqondiso; eyesithathu yi-EMI eveliswe yincam ye-engile ekunene.

I-parasite capacitance ebangelwa yi-engile echanekileyo yomgca wothumelo ingabalwa ngale fomula yobungqina:

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

Kule fomula ingasentla, uC ubhekisa kumthamo olinganayo wekona (iyunithi: pF), uW ubhekisa kububanzi bomkhondo (iyunithi: intshi), u-εr ubhekisa kwidielectric engaguqukiyo yesiphakathi, kwaye uZ0 luphawu lokuthintela. yomgca wothumelo. Umzekelo, kwi-4Mils 50 umgca wothumelo we-ohm (εr yi-4.3), i-capacitance eziswa yi-angle echanekileyo malunga ne-0.0101pF, kwaye emva koko utshintsho lwexesha lokunyuka olubangelwa oku lunokuqikelelwa:

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

Inokubonwa ngokubala ukuba isiphumo se-capacitance eziswa yi-right-angle trace incinci kakhulu.

Njengoko ububanzi bomgca we-right-angle trace inyuka, i-impedance apho iya kuncipha, ngoko ke into ethile yokubonakalisa umqondiso iya kwenzeka. Singakwazi ukubala i-impedance elinganayo emva kokuba ububanzi bomgca bunyukile ngokwefomula yokubala ye-impedance ekhankanywe kwisahluko somgca wothumelo, kwaye emva koko Bala i-coefficient yokubonakalisa ngokwe-empirical formula:

ρ=(Zs-Z0)/(Zs+Z0)

Ngokuqhelekileyo, utshintsho lwe-impedance olubangelwa i-wiring ye-right-angle iphakathi kwe-7% -20%, ngoko ke i-coefficient yokubonisa ubuninzi malunga ne-0.1. Ngaphezu koko, njengoko kunokubonwa kumfanekiso ongezantsi, i-impedance yomzila wokuhambisa utshintshela ubuncinane phakathi kobude be-W / 2 umgca, kwaye ubuyele kwi-impedance eqhelekileyo emva kwexesha le-W / 2. Lonke ixesha lokutshintsha kwe-impedance lifutshane kakhulu, rhoqo ngaphakathi kwe-10ps. Ngaphakathi, olo tshintsho lukhawulezayo kunye noluncinci luphantse lungabinamsebenzi wokuhambisa umqondiso jikelele.

Abantu abaninzi banolu lwazi lwe-wiring ye-right-angle. Bacinga ukuba incam kulula ukuyihambisa okanye ukufumana amaza ombane kunye nokwenza i-EMI. Oku kube sesinye sezizathu ezibangela ukuba abantu abaninzi bacinge ukuba i-engile-engile yocingo ayinakuhanjiswa. Nangona kunjalo, uninzi lweziphumo zokwenyani zovavanyo zibonisa ukuba umkhondo ochanekileyo awuzukuvelisa i-EMI ecacileyo kunemigca ethe tye. Mhlawumbi ukusebenza kwesixhobo esikhoyo kunye nenqanaba lovavanyo lithintela ukuchaneka kovavanyo, kodwa ubuncinci libonisa ingxaki. I-radiation ye-wiring ene-angled ekunene sele incinci kunempazamo yokulinganisa isixhobo ngokwawo.

Ngokubanzi, indlela ye-engile ekunene ayiyoyiki njengoko kucingelwa. Ubuncinci kwizicelo ezingaphantsi kweGHz, naziphi na iziphumo ezinjengokukwazi, ukubonakalisa, i-EMI, njl njl. azibonakali kuvavanyo lwe-TDR. Iinjineli zoyilo zePCB ezinesantya esiphezulu kusafuneka zigxile kuyilo, amandla / uyilo lomhlaba, kunye noyilo lweengcingo. Ngemingxuma kunye neminye imiba. Ngokuqinisekileyo, nangona impembelelo ye-wiring ye-right angle ayinzima kakhulu, ayithethi ukuba sonke sinokusebenzisa i-wiring ye-right-angle kwixesha elizayo. Ukuthathela ingqalelo kwiinkcukacha ngowona mgangatho usisiseko ekufuneka zonke iinjineli ezilungileyo zibe nazo. Ngaphezu koko, ngophuhliso olukhawulezayo lweesekethe zedijithali, i-PCB Ukuphindaphinda komqondiso ocutshungulwayo ziinjineli ziya kuqhubeka nokukhula. Kwintsimi yoyilo lweRF ngaphezulu kwe-10GHz, ezi engile zincinci zasekunene zinokuba lugxininiso lweengxaki zesantya esiphezulu.

2. Indlela eyahlukileyo

Isignali eyahlukileyo (DifferentialSignal) isetyenziswa ngokubanzi kuyilo lwesekethe yesantya esiphezulu. Isibonakaliso esibaluleke kakhulu kwisiphaluka sihlala siyilwe ngesakhiwo esahlukileyo. Yintoni eyenza idume kangaka? Ukuqinisekisa njani ukusebenza kakuhle kuyilo lwePCB? Ngale mibuzo mibini, siqhubela phambili kwinxalenye elandelayo yengxoxo.

Yintoni umqondiso wokwahlula? Ngokwemigaqo ye-layman, isiphelo sokuqhuba sithumela izibonakaliso ezimbini ezilinganayo kunye ne-inverted, kwaye isiphelo sokufumana sigweba i-logic state “0” okanye “1” ngokuthelekisa umahluko phakathi kwee-voltages ezimbini. Izibini zemikhondo ethwele imiqondiso eyahlukileyo ibizwa ngokuba yimizila eyahlukileyo.

Xa kuthelekiswa nezalathisi eziqhelekileyo ezinesiphelo esinye, imiqondiso eyahlukileyo inezona nzuzo zicacileyo kule miba mithathu ilandelayo:

a. Ikhono elinamandla lokuchasana nokuphazamiseka, kuba ukudibanisa phakathi kweendlela ezimbini ezihlukeneyo kukuhle kakhulu. Xa kukho ukuphazamiseka kwengxolo evela ngaphandle, baphantse badityaniswe kwimigca emibini ngaxeshanye, kwaye isiphelo sokufumana sikhathalele kuphela umahluko phakathi kwemiqondiso emibini. Ngoko ke, ingxolo yemowudi eqhelekileyo yangaphandle inokurhoxiswa ngokupheleleyo. b. Inokucinezela ngempumelelo i-EMI. Ngesizathu esifanayo, ngenxa ye-polarity echaseneyo yemiqondiso emibini, imimandla ye-electromagnetic ekhutshwe ngabo inokucima enye kwenye. Okukhona umanyano luqina, kokukhona kuncipha amandla ombane wombane angena kwihlabathi langaphandle. c. Ukubekwa kwexesha kuchanekile. Ngenxa yokuba utshintsho lokutshintsha komqondiso wokwahlukana lubekwe ekudibaneni kweempawu ezimbini, ngokungafaniyo nomqondiso oqhelekileyo owodwa, oxhomekeke kumandla aphezulu kunye nomgangatho ophantsi wokumisela, awuchatshazelwa kancinci yinkqubo kunye nobushushu, obunokuthi ukunciphisa imposiso kwixesha. , Kodwa kwakhona kufanelekile ngakumbi kwiisekethe zesignali ezisezantsi-amplitude. I-LVDS yangoku edumileyo (i-lowvoltagedifferentialsignaling) ibhekisa kobu buchwephesha besignali ye-amplitude encinci.

Kwiinjineli ze-PCB, eyona nto ixhalabisayo yindlela yokuqinisekisa ukuba ezi nzuzo zokwahlukana kweengcingo zingasetyenziswa ngokupheleleyo kwiintambo zokwenyani. Mhlawumbi nabani na oye wadibana ne-Layout uya kuqonda iimfuno eziqhelekileyo ze-wiring yokwahlukana, oko kukuthi, “ubude obulinganayo kunye nomgama olinganayo”. Ubude obulinganayo kukuqinisekisa ukuba izibonakaliso ezimbini ezihlukeneyo zigcina i-polarity ezichaseneyo ngamaxesha onke kwaye zinciphisa icandelo lemowudi eqhelekileyo; umgama olinganayo ubukhulu becala kukuqinisekisa ukuba i-impedances yokwahlukana kwezi zimbini zihambelana kwaye zinciphisa ukubonakaliswa. “Ngokusondeleyo kangangoko kunokwenzeka” ngamanye amaxesha enye yeemfuno ze-wiring yokwahlukana. Kodwa yonke le migaqo ayisetyenziswanga ukuba isebenze ngoomatshini, kwaye iinjineli ezininzi zibonakala ngathi azikayiqondi eyona njongo yokuhanjiswa komqondiso wesantya esiphezulu.

Oku kulandelayo kugxininise ekungaqondani okuqhelekileyo kuyilo lophawu lomahluko wePCB.

Ukungaqondi kakuhle i-1: Kukholelwa ukuba isignali yokwahlukana ayifuni inqwelomoya ephantsi njengendlela yokubuya, okanye ukuba iindlela ezihlukeneyo zibonelela ngendlela yokubuyela komnye nomnye. Isizathu salokhu kungaqondi kakuhle kukuba badideke ngeziganeko ezingaphezulu, okanye indlela yokuhanjiswa kwesignali yesantya esiphezulu ayinzulu ngokwaneleyo. Inokubonwa kwisakhiwo sokufumana isiphelo soMfanekiso 1-8-15 ukuba imisinga emitter ye-transistors Q3 kunye ne-Q4 iyalingana kwaye ichasene, kwaye imisinga yazo emhlabeni irhoxisa ngokuthe ngqo (I1 = 0), ngoko ke isekethe yokwahluka yi-bounces efanayo kunye nezinye iimpawu zengxolo ezinokubakho kumandla kunye neenqwelomoya zomhlaba azinamvakalelo. Ukucinywa kokubuyiswa kwenxalenye yendiza yomhlaba akuthethi ukuba isiphaluka esahlukileyo asisebenzisi indiza yereferensi njengendlela yokubuyisela umqondiso. Enyanisweni, kuhlalutyo lokubuyiswa komqondiso, indlela yokudibanisa i-wiring kunye ne-wiring eqhelekileyo i-single-end iyafana, oko kukuthi, izibonakaliso eziphezulu ze-frequency zihlala zi-Reflow kunye ne-loop kunye neyona inductance encinci, umahluko omkhulu kukuba ngaphezu koko. ukudibanisa emhlabeni, umgca wokwahlukana nawo unokudibanisa. Luluphi uhlobo lokudibanisa olomeleleyo, leliphi eliba yindlela ephambili yokubuya. Umzobo we-1-8-16 ngumzobo we-schematic we-geomagnetic field distribution of signing single-end kunye neempawu ezahlukileyo.

Kuyilo lwesekethe ye-PCB, ukudityaniswa phakathi komkhondo wokwahlukana kuncinci, ngokufuthi kubalwa kuphela kwi-10 ukuya kwi-20% yedigri yokudibanisa, kwaye ngaphezulu kukudityaniswa komhlaba, ngoko ke eyona ndlela iphambili yokubuya komkhondo wokwahlukana isekhona emhlabeni. inqwelomoya . Xa i-plane yomhlaba inqanyuliwe, ukudibanisa phakathi kweendlela ezihlukeneyo kuya kunika indlela ephambili yokubuyela kwindawo ngaphandle kwendiza yokubhekisela, njengoko kuboniswe kuMfanekiso 1-8-17. Nangona impembelelo yokungaqhubeki kwinqwelo-moya yesalathiso kwi-trace eyahlulayo ayinzima njengaleyo yomzila oqhelekileyo ogqityiweyo, iya kunciphisa umgangatho wesignali yokwahlukana kunye nokwandisa i-EMI, ekufuneka igwenywe kangangoko kunokwenzeka. . Abanye abaqulunqi bakholelwa ukuba inqwelomoya yesalathiso phantsi komkhondo ohlukeneyo inokususwa ukucinezela imiqondiso ethile yemowudi eqhelekileyo ekuhanjisweni okwahlukileyo. Nangona kunjalo, le ndlela ayinqweneleki kwithiyori. Indlela yokulawula i-impedance? Ukungaboneleli ngeluphu yothintelo lomhlaba kwisignali yendlela eqhelekileyo ngokuqinisekileyo kuya kubangela imitha ye-EMI. Le ndlela yenza umonakalo omkhulu kunokulunga.

Ukungaqondi kakuhle 2: Kukholelwa ukuba ukugcina izithuba ezilinganayo kubaluleke kakhulu kunokuthelekisa ubude bomgca. Kuyilo lwePCB olululo, kaninzi akunakwenzeka ukuhlangabezana neemfuno zoyilo lolwahlulo ngaxeshanye. Ngenxa yobukho bosasazo lwephini, i-vias, kunye nesithuba sokuvala iintambo, injongo yokulinganisa ubude bomgca kufuneka iphunyezwe ngokujija ngokufanelekileyo, kodwa isiphumo kufuneka sibe kukuba ezinye iindawo zesibini sokwahluka azikwazi ukunxulunyaniswa. Yintoni esifanele siyenze ngeli xesha? Loluphi ukhetho? Ngaphambi kokuthatha izigqibo, makhe sijonge ezi ziphumo zilandelayo zokulinganisa.

Ukususela kwezi ziphumo zokulinganisa zingentla, kunokubonwa ukuba iifom zamaza zeSkimu 1 kunye neSikimu sesi-2 ziphantse zifane, oko kukuthi, impembelelo ebangelwa ukungalingani kwesithuba esincinci. Xa kuthelekiswa, iimpembelelo zobude obungahambelaniyo bomgca kwixesha elide kakhulu. (Isicwangciso sesi-3). Ukususela kuhlalutyo lwethiyori, nangona isithuba esingahambelaniyo siya kubangela ukuba ukuchaphazeleka okungafaniyo kutshintshe, kuba ukudibanisa phakathi kwesibini esahlukileyo ngokwaso akubalulekanga, uluhlu lotshintsho lwe-impedance luncinci kakhulu, ngokuqhelekileyo ngaphakathi kwe-10%, elilingana kuphela nokupasa omnye. . Ukubonakaliswa okubangelwa ngumngxuma akuyi kuba nempembelelo ebalulekileyo ekuhanjisweni komqondiso. Emva kokuba ubude bomgca abuhambelani, ukongeza kwi-offset yexesha, amacandelo emowudi eqhelekileyo angeniswa kwisignali yokwahlukana, okunciphisa umgangatho wesignali kunye nokwandisa i-EMI.

Kunokuthiwa owona mgaqo ubalulekileyo kuyilo lwe-PCB yokwahlukana kweempawu ubude bomgca ohambelanayo, kunye neminye imithetho inokuphathwa ngokuguquguqukayo ngokweemfuno zoyilo kunye nezicelo eziphathekayo.

Ukungaqondi kakuhle 3: Cinga ukuba i-wiring yokwahlukana kufuneka isondele kakhulu. Ukugcina umkhondo wokwahlula ukufutshane akukho nto ingaphaya kokuphucula ukudityaniswa kwawo, okunokuthi kungaphuculi kuphela ukungakhuseleki kwingxolo, kodwa nokusebenzisa ngokupheleleyo i-polarity echasene nemagnethi ukuphelisa ukuphazamiseka kwe-electromagnetic kwihlabathi langaphandle. Nangona le ndlela iluncedo kakhulu kwiimeko ezininzi, ayiphelelanga. Ukuba sinokuqinisekisa ukuba zikhuseleke ngokupheleleyo ekuphazamisekeni kwangaphandle, ngoko akufuneki ukuba sisebenzise ukudibanisa okuqinileyo ukufezekisa ukuchasana nokuphazamiseka. Kwaye injongo yokucinezela i-EMI. Singenza njani ukuze siqinisekise ukwahlulwa okufanelekileyo kunye nokukhuselwa kwemikhondo eyahlukileyo? Ukwandisa izithuba kunye nezinye iimpawu zesignali yenye yezona ndlela zisisiseko. I-electromagnetic field energy iyancipha ngesikwere somgama. Ngokuqhelekileyo, xa isithuba somgca sidlula amaxesha ama-4 ububanzi bomgca, ukuphazamiseka phakathi kwabo kubuthathaka kakhulu. Inokungahoywa. Ukongeza, ukuhlukaniswa ngenqwelomoya ephantsi kunokudlala indima entle yokukhusela. Esi sakhiwo sisoloko sisetyenziswa kwi-high-frequency (ngaphezulu kwe-10G) i-IC iphakheji yoyilo lwe-PCB. Ibizwa ngokuba sisakhiwo se-CPW, esinokuqinisekisa ukungafani okungqongqo. Ulawulo (2Z0), njengoko kuboniswe kuMfanekiso 1-8-19.

Umkhondo ohlukeneyo unokusebenza kwiimpawu ezahlukeneyo, kodwa le ndlela ayikhuthazwa ngokubanzi, kuba iyantlukwano kwi-impedance kunye ne-vias eveliswa ngamaleko ahlukeneyo iya kutshabalalisa isiphumo sothumelo lwemo yokwahlukana kwaye yazise ingxolo yemowudi eqhelekileyo. Ukongeza, ukuba iileya ezimbini ezikufutshane azidityaniswanga ngokuqinileyo, oko kuya kunciphisa amandla okulandela umkhondo wokuxhathisa ingxolo, kodwa ukuba unokugcina umgama ofanelekileyo ukusuka kwimizila ejikelezileyo, i-crosstalk ayiyongxaki. Kwiifrikhwensi ngokubanzi (ngezantsi kwe-GHz), i-EMI ayiyi kuba yingxaki enkulu. Iimvavanyo zibonise ukuba ukuthotywa kwamandla ombane kumgama we-500 mils ukusuka kumkhondo ohlukeneyo kuye kwafikelela kwi-60 dB kumgama weemitha ezi-3, okwaneleyo ukuhlangabezana nomgangatho wemitha ye-electromagnetic yeFCC, ngoko ke uMyili akanaxhala naye. kakhulu malunga nokungahambelani kwe-electromagnetic okubangelwa kukungonelanga kokudibanisa umgca womahluko.

3. Umgca wenyoka

Umgca wenyoka luhlobo lwendlela yomzila ehlala isetyenziswa kuLuhlulo. Eyona njongo yayo kukulungelelanisa ukulibaziseka ukuhlangabezana neemfuno zoyilo lwexesha lenkqubo. Umyili kufuneka aqale abe nale ngqiqo: umgca wenyoka uya kutshabalalisa umgangatho wesignali, utshintshe ukulibaziseka kokuhanjiswa, kwaye uzame ukuphepha ukuyisebenzisa xa udibanisa. Nangona kunjalo, kuyilo lwangempela, ukuze kuqinisekiswe ukuba umqondiso unexesha elaneleyo lokubamba, okanye ukunciphisa ixesha lokunciphisa phakathi kweqela elifanayo leempawu, kudla ngokuyimfuneko ukuvuthuza ngamabomu ucingo.

Ke, ithini ifuthe lentambo yenyoka ekugqithiseni umqondiso? Yintoni endimele ndiyinikele ingqalelo xa i-wiring? Iiparamitha ezimbini ezibaluleke kakhulu ubude bokudibanisa (Lp) kunye nomgama wokudibanisa (S), njengoko kubonisiwe kuMfanekiso 1-8-21. Ngokucacileyo, xa umqondiso uhanjiswa kumkhondo wenyoka, iisegmenti zomgca ohambelanayo ziya kudibaniswa kwimodi yokwahlula. Incinci i-S kunye ne-Lp enkulu, inkulu iqondo lokudibanisa. Inokubangela ukuba ukulibaziseka kokudluliselwa kuncitshiswe, kwaye umgangatho wesignali uyancipha kakhulu ngenxa ye-crosstalk. Isixhobo singabhekisa kuhlalutyo lwemowudi eqhelekileyo kunye nemo yokwahlula-hlula i-crosstalk kwiSahluko sesi-3.

Ezi zilandelayo zezinye iingcebiso zeenjineli zeLayout xa zisebenza ngemigca yenyoka:

1. Zama ukwandisa umgama (S) wamacandelo omgca ohambelanayo, ubuncinane obukhulu kune-3H, i-H ibhekisela kumgama osuka kumkhondo wesignali ukuya kwinqwelo-moya. Ngokwabantu abaqhelekileyo, kukujikeleza igophe elikhulu. Logama nje i-S inkulu ngokwaneleyo, isiphumo sokudityaniswa kwe-mutual coupling siphantse saphetshwa ngokupheleleyo. 2. Nciphisa ubude bokudibanisa Lp. Xa ukulibaziseka kwe-Lp kabini kusondela okanye kudlula ixesha lokunyuka kwesignali, i-crosstalk eyenziwe iya kufikelela kwi-saturation. 3. Ukulibaziseka kokuhanjiswa kwesignali okubangelwa ngumgca wenyoka we-Strip-Line okanye i-Embedded Micro-strip ingaphantsi kwe-Micro-strip. Kwithiyori, i-stripline ayiyi kuchaphazela ireyithi yothumelo ngenxa yendlela yokwahlukana kwe-crosstalk. 4. Kwimigca yomqondiso wesantya esiphezulu kunye nezo zineemfuno ezingqongqo zexesha, zama ukungasebenzisi imigca yenyoka, ngakumbi kwiindawo ezincinci. 5. Ungahlala usebenzisa i-serpentine traces nakweyiphi na i-angle, njengesakhiwo se-C kwi-Figure 1-8-20, enokunciphisa ngokufanelekileyo ukudibanisa ngokubambisana. 6. Kwi-PCB yoyilo lwe-high-speed, umgca wenyoka awunayo into ebizwa ngokuba yi-filtering okanye i-anti-interference, kwaye inokunciphisa kuphela umgangatho wesignali, ngoko isetyenziselwa ukulinganisa ixesha kwaye ayikho enye injongo. 7. Ngamanye amaxesha ungacinga ngokujija ngendlela ejikelezayo. Ukulinganisa kubonisa ukuba umphumo wayo ungcono kunendlela eqhelekileyo yenyoka.