Inani labaqulunqi bedijithali kunye neengcali zoyilo lwebhodi yesekethe yedijithali kwicandelo lobunjineli lihlala lisanda, elibonisa indlela yophuhliso lweshishini. Nangona ugxininiso kuyilo lwedijithali luzise uphuhliso olukhulu kwiimveliso ze-elektroniki, lusekho, kwaye kuya kuhlala kukho uyilo oluthile lwesekethe olujongana ne-analog okanye iimeko zokwenyani. Izicwangciso zocingo kwiinkalo ze-analog kunye nedijithali zinezinye izinto ezifanayo, kodwa xa ufuna ukufumana iziphumo ezingcono, ngenxa yezicwangciso zabo ezahlukeneyo zocingo, ukucwangciswa kwe-wiring yesekethe elula akusekho isisombululo esifanelekileyo.

Eli nqaku lixubusha ukufana okusisiseko kunye nokwahlukana phakathi kwe-analog kunye ne-digital wiring ngokubhekiselele kwi-bypass capacitors, ukunikezelwa kwamandla, ukuyila komhlaba, iimpazamo zombane, kunye nokuphazamiseka kwe-electromagnetic interference (EMI) okubangelwa i-PCB wiring.

Inani labaqulunqi bedijithali kunye neengcali zoyilo lwebhodi yesekethe yedijithali kwicandelo lobunjineli lihlala lisanda, elibonisa indlela yophuhliso lweshishini. Nangona ugxininiso kuyilo lwedijithali luzise uphuhliso olukhulu kwiimveliso ze-elektroniki, lusekho, kwaye kuya kuhlala kukho uyilo oluthile lwesekethe olujongana ne-analog okanye iimeko zokwenyani. Izicwangciso zocingo kwiinkalo ze-analog kunye nedijithali zinezinye izinto ezifanayo, kodwa xa ufuna ukufumana iziphumo ezingcono, ngenxa yezicwangciso zabo ezahlukeneyo zocingo, ukucwangciswa kwe-wiring yesekethe elula akusekho isisombululo esifanelekileyo.

Eli nqaku lixubusha ukufana okusisiseko kunye nokwahlukana phakathi kwe-analog kunye ne-digital wiring ngokubhekiselele kwi-bypass capacitors, ukunikezelwa kwamandla, ukuyila komhlaba, iimpazamo zombane, kunye nokuphazamiseka kwe-electromagnetic interference (EMI) okubangelwa i-PCB wiring.

Ukongeza i-bypass okanye i-decoupling capacitors kwibhodi yesiphaluka kunye nendawo yala ma-capacitors ebhodini yingqiqo eqhelekileyo yoyilo lwedijithali kunye ne-analog. Kodwa okubangel’ umdla kukuba, izizathu zahlukile.

Kuyilo lwe-analog wiring, i-bypass capacitors idla ngokusetyenziselwa ukugqitha imiqondiso ye-frequency ephezulu kunikezelo lwamandla. Ukuba i-bypass capacitors ayidityaniswanga, ezi zibonakaliso ze-frequency ephezulu zinokungena kwiitshiphu ze-analog ezibuthathaka ngokusebenzisa izikhonkwane zonikezelo lwamandla. Ngokuqhelekileyo, ukuphindaphinda kwezi zibonakaliso ze-frequency ephezulu kudlula amandla ezixhobo ze-analog ukucinezela izibonakaliso eziphezulu. Ukuba i-bypass capacitor ayisetyenziswanga kwisekethe ye-analog, ingxolo inokwaziswa kwindlela yomqondiso, kwaye kwiimeko ezinzulu kakhulu, inokubangela ukungcangcazela.

Kuyilo lwe-analog kunye nedijithali yePCB, i-bypass okanye i-decoupling capacitors (0.1uF) kufuneka ibekwe kufutshane nesixhobo kangangoko kunokwenzeka. I-capacitor yokuqhawula umbane (10uF) kufuneka ibekwe kwindawo yokungena yombane webhodi yesekethe. Kuzo zonke iimeko, izikhonkwane zala ma-capacitors kufuneka zibe zifutshane.

Kwibhodi yesiphaluka kwi-Figure 2, iindlela ezahlukeneyo zisetyenziselwa ukuhambisa amandla kunye neengcingo zomhlaba. Ngenxa yale ntsebenziswano ingafanelekanga, amacandelo e-elektroniki kunye neesekethe kwibhodi yesekethe kunokwenzeka ukuba zibe phantsi kokuphazamiseka kombane.

Kwiphaneli enye yoMfanekiso 3, amandla kunye neengcingo zomhlaba kumacandelo ebhodini leesekethe zisondele omnye komnye. Umlinganiselo ohambelanayo womgca wamandla kunye nomgca womhlaba kule bhodi yesekethe ufanelekile njengoko kuboniswe kuMfanekiso 2. Amathuba amacandelo e-elektroniki kunye neesekethe kwibhodi yesekethe ephantsi kokuphazamiseka kwe-electromagnetic interference (EMI) iyancipha ngamaxesha angama-679 / 12.8 okanye malunga namaxesha angama-54.
　　
Kwizixhobo zedijithali ezifana nabalawuli kunye neeprosesa, i-decoupling capacitors nayo iyafuneka, kodwa ngenxa yezizathu ezahlukeneyo. Omnye umsebenzi wezi capacitors kukusebenza njengebhanki yentlawulo "encinci".

Kwiisekethe zedijithali, inani elikhulu langoku lidla ngokufunwa ukwenza ukutshintshwa kombuso wesango. Ekubeni ukutshintshwa kwee-current currents ziveliswa kwi-chip ngexesha lokutshintsha kunye nokuhamba ngebhodi yesiphaluka, kunenzuzo ukuba neentlawulo ezongezelelweyo "ze-spare". Ukuba akukho ntlawulo yaneleyo xa usenza isenzo sokutshintsha, i-voltage yombane iya kutshintsha kakhulu. Ukutshintsha kwamandla ombane amaninzi kakhulu kuya kubangela inqanaba lophawu lwedijithali ukuba lingene kwimeko yokungaqiniseki, kwaye kunokubangela ukuba umatshini welizwe okwisixhobo sedijithali usebenze ngokungalunganga.

Ukutshintshwa kwangoku ojikelezayo kwi-trace yebhodi yesiphaluka kuya kubangela ukuba i-voltage itshintshe, kwaye ibhodi yebhodi yesiphaluka ilandelelanisa i-parasitic inductance. Le fomula ilandelayo ingasetyenziselwa ukubala utshintsho lombane: V = LdI/dt. Phakathi kwazo: V = utshintsho lwe-voltage, L = ibhodi yesiphaluka i-trace inductance, dI = utshintsho lwangoku ngokulandela umkhondo, dt = ixesha lokutshintsha kwangoku.
　　
Ngoko ke, ngenxa yezizathu ezininzi, kungcono ukusebenzisa i-bypass (okanye i-decoupling) i-capacitors kunikezelo lwamandla okanye kwizikhonkwane zombane zezixhobo ezisebenzayo.

Intambo yamandla kunye nocingo oluphantsi kufuneka luhanjiswe kunye

Indawo yentambo yamandla kunye nocingo olusemhlabeni luhambelana kakuhle ukuze kuncitshiswe uphazamiseko lwe-electromagnetic. Ukuba intambo yamandla kunye nomgca osezantsi azihambelani ngokufanelekileyo, iluphu yenkqubo iya kuyilwa kwaye ingxolo iya kuveliswa.

Umzekelo woyilo lwePCB apho intambo yombane kunye nomgca osezantsi zingahambelani ngokufanelekileyo ubonisiwe kuMfanekiso 2. Kule bhodi yesekethe, indawo eyilo eyilophu yi-697cm². Ukusebenzisa indlela eboniswe kwi-Figure 3, ukuba nokwenzeka kwengxolo ye-radiated okanye ngaphandle kwebhodi yesekethe yokunyusa i-voltage kwi-loop inokunciphisa kakhulu.

Umahluko phakathi kwe-analog kunye nezicwangciso ze-wiring zedijithali

▍Inqwelo-moya ephantsi yingxaki

Ulwazi olusisiseko lwe-wiring yebhodi yesekethe lusebenza kuzo zombini iisekethe ze-analog kunye nedijithali. Umgaqo osisiseko wobhontsi kukusebenzisa inqwelomoya ephantsi engaphazanyiswa. Le ngqiqo inciphisa i-dI / dt (utshintsho lwangoku kunye nexesha) kwiisekethe zedijithali, ezitshintsha amandla omhlaba kwaye zibangele ingxolo yokungena kwiisekethe ze-analog.

Ubuchwephesha bocingo lwedijithali kunye neesekethe ze-analog ziyafana ngokusisiseko, ngaphandle kokunye. Kwiisekethe ze-analog, kukho enye ingongoma ekufuneka uyiqaphele, oko kukuthi, gcina imigca yesignali yedijithali kunye ne-loops kwi-plane yomhlaba kude kude kwiisekethe ze-analog ngokunokwenzeka. Oku kunokufezekiswa ngokudibanisa i-analog yendiza yomhlaba kwi-system uxhulumaniso lomhlaba ngokwahlukileyo, okanye ukubeka isiphaluka se-analog ekupheleni kwebhodi yesekethe, ekupheleni komgca. Oku kwenziwa ukugcina uphazamiseko lwangaphandle kwindlela yomqondiso ubuncinane.

Akukho mfuneko yokwenza oku kwiisekethe zedijithali, ezinokunyamezela ingxolo eninzi kwi-plane yomhlaba ngaphandle kweengxaki.

Umzobo we-4 (ngasekhohlo) uhlukanisa isenzo sokutshintsha kwedijithali ukusuka kwisiphaluka se-analog kwaye sahlula iinxalenye zedijithali kunye ne-analog yesiphaluka. (Ekunene) I-frequency ephezulu kunye ne-frequency ephantsi kufuneka ihlulwe ngokusemandleni, kwaye amacandelo aphezulu kufuneka abe kufuphi nezixhumi zebhodi yesekethe.

Umzobo 5 Ukuseta imikhondo emibini ekufutshane kwi-PCB, kulula ukwenza i-parasitic capacitance. Ngenxa yobukho bolu hlobo lwe-capacitance, utshintsho olukhawulezayo lombane kumkhondo omnye lunokuvelisa uphawu lwangoku komnye umkhondo.

Umzobo 6 Ukuba awuhoyi ngqalelo ekubekweni kwemikhondo, imikhondo kwi-PCB inokuvelisa i-line inductance kunye ne-mutual inductance. Le inductance parasitic iyingozi kakhulu ekusebenzeni kweesekethe ezibandakanya iisekethe zokutshintsha idijithali.

▍Indawo yecandelo

Njengoko kukhankanyiwe ngasentla, kwi-design ye-PCB nganye, inxalenye yengxolo yesiphaluka kunye nenxalenye "ezolileyo" (inxalenye engeyiyo ingxolo) kufuneka ihlulwe. Ngokuqhelekileyo, iisekethe zedijithali "zityebile" kwingxolo kwaye azinamvakalelo kwingxolo (kuba iisekethe zedijithali zinonyamezelo olukhulu lwengxolo yombane); ngokuchaseneyo, ukunyamezela ingxolo yombane kwiisekethe ze-analog kuncinci kakhulu.

Kwezi zimbini, iisekethe ze-analog zezona zinovakalelo kwingxolo yokutshintsha. Kwi-wiring ye-system-signal system, ezi zijikelezo ezimbini kufuneka zihlulwe, njengoko kuboniswe kuMzobo 4.
　　
▍Amalungu eParasitic aveliswa luyilo lwePCB

Izinto ezimbini ezisisiseko se-parasitic ezinokubangela iingxaki zenziwe ngokulula kuyilo lwe-PCB: i-parasitic capacitance kunye ne-parasitic inductance.

Xa uyila ibhodi yesiphaluka, ukubeka imikhondo emibini ngokusondeleyo komnye kuya kuvelisa i-parasitic capacitance. Unokwenza oku: Kwimigangatho emibini eyahlukeneyo, beka umkhondo omnye phezu komnye; okanye kuluhlu olufanayo, beka umkhondo omnye ecaleni komnye, njengoko kubonisiwe kumfanekiso wesi-5.
　　
Kolu lungelelwaniso lokulandela umkhondo kubini, utshintsho kumbane ekuhambeni kwexesha (dV/dt) kumkhondo omnye kunokubangela ukuba kubekho okwangoku komnye umkhondo. Ukuba enye i-trace i-impedance ephezulu, yangoku eyenziwa yintsimi yombane iya kuguqulwa ibe yi-voltage.
　　
Ukutshintsha kombane okhawulezayo kaninzi kwenzeka kwicala ledijithali loyilo lophawu lwe-analog. Ukuba ulandelelwano olune-voltage transients olukhawulezayo lusondele kwi-high-impedance traces ye-analog, le mpazamo iya kuchaphazela kakhulu ukuchaneka kwesekethe ye-analog. Kule meko, iisekethe ze-analog zineengxaki ezimbini: ukunyamezela kwabo ingxolo kuphantsi kakhulu kuneesekethe zedijithali; kwaye imikhondo ephezulu ye-impedance ixhaphake kakhulu.
　　
Ukusebenzisa enye yezi ndlela zimbini zilandelayo kunokunciphisa le nto. Eyona ndlela isetyenziswa ngokuqhelekileyo kukutshintsha ubungakanani phakathi kweetrayisi ngokwecapacitance equation. Obona bukhulu busebenzayo bokutshintsha ngumgama phakathi kwemikhondo emibini. Kufuneka kuqatshelwe ukuba i-variable d ikwidinomineyitha ye-capacitance equation. Njengoko i-d inyuka, i-capacitive reactance iya kuncipha. Olunye uguquko olunokutshintshwa bubude bemikhondo emibini. Kule meko, ubude be-L buyancipha, kwaye ukusabela kwe-capacitive phakathi kweendlela ezimbini kuya kuncipha.
　　
Obunye ubuchule kukufaka ucingo olusemhlabeni phakathi kwale mikhondo mibini. Ucingo oluphantsi lune-impedance ephantsi, kwaye ukongeza omnye umkhondo onje kuya kwenza buthathaka intsimi yombane yokuphazamiseka, njengoko kubonisiwe kuMfanekiso 5.
　　
Umgaqo we-parasitic inductance kwibhodi yesiphaluka ufana ne-parasitic capacitance. Kukwandlala imikhondo emibini. Kwimigangatho emibini eyahlukeneyo, beka umkhondo omnye phezu komnye; okanye kuluhlu olufanayo, beka umkhondo omnye ecaleni komnye, njengoko kubonisiwe kuMfanekiso 6.

Kule mibini mibini yokucwangciswa kwee-wiring, utshintsho lwangoku (dI/dt) lomkhondo kunye nexesha, ngenxa ye-inductance yalo mkhondo, luya kuvelisa i-voltage kumkhondo ofanayo; kwaye ngenxa yobukho be-mutual inductance, iya kuba I-proportional current iveliswa komnye umkhondo. Ukuba utshintsho lwe-voltage kumkhondo wokuqala lukhulu ngokwaneleyo, ukuphazamiseka kunokunciphisa ukunyamezela kombane wesekethe yedijithali kwaye kubangele iimpazamo. Esi siganeko asenzeki kuphela kwiisekethe zedijithali, kodwa le nto ixhaphake kakhulu kwiisekethe zedijithali ngenxa yeendlela ezinkulu zokutshintsha ngokukhawuleza kwiisekethe zedijithali.
　　
Ukuphelisa ingxolo enokubakho kwimithombo yokuphazamiseka kwe-electromagnetic, kungcono ukwahlula imigca ye-analog "ezolileyo" kumazibuko e-I/O anomsindo. Ukuzama ukufezekisa umbane ophantsi kwe-impedance kunye nenethiwekhi yomhlaba, i-inductance yeentambo zeesekethe zedijithali kufuneka zincitshiswe, kwaye ukudibanisa i-capacitive yeesekethe ze-analog kufuneka kuncitshiswe.
　　
03

Ukuqukumbela

Emva kokuba uluhlu lwedijithali kunye ne-analog lumisiwe, ukuhambisa ngononophelo kubalulekile kwi-PCB eyimpumelelo. Isicwangciso se-Wiring sivame ukwaziswa kuwo wonke umntu njengomgaqo wesithupha, kuba kunzima ukuvavanya impumelelo yokugqibela yemveliso kwindawo yebhubhoratri. Ngoko ke, nangona ukufana kwezicwangciso zocingo zedijithali kunye neesekethe ze-analog, ukuhlukana kwezicwangciso zabo zocingo kufuneka kuqatshelwe kwaye kuthathwe ngokungathí sina.