Ingabe kufanele kuhlukaniswe izingqimba zomhlabathi ze-AGND ne-DGND?
Impendulo elula iwukuthi kuya ngesimo, futhi impendulo enemininingwane ukuthi ngokuvamile abahlukani.Ngoba ezimweni eziningi, ukuhlukanisa ungqimba lomhlabathi kuzokwandisa kuphela i-inductance ye-return current, okuletha umonakalo omkhulu kunokuhle.Ifomula V = L(di/dt) ikhombisa ukuthi njengoba i-inductance ikhula, umsindo we-voltage uyanda.Futhi njengoba ukushintshwa kwamanje kukhuphuka (ngoba izinga lesampula lesiguquli liyakhula), umsindo we-voltage nawo uzokhula.Ngakho-ke, izingqimba zomhlabathi kufanele zixhunywe ndawonye.
Isibonelo siwukuthi kwezinye izinhlelo zokusebenza, ukuze kuhambisane nezidingo zomklamo wendabuko, amandla ebhasi angcolile noma i-digital circuitry kufanele ibekwe ezindaweni ezithile, kodwa futhi ngezingqinamba zosayizi, okwenza ibhodi lingakwazi ukufeza ukwahlukanisa okuhle kwesakhiwo, kulokhu. icala, isendlalelo esiphansi esihlukile siyisihluthulelo sokufeza ukusebenza okuhle.Kodwa-ke, ukuze umklamo jikelele uphumelele, lezi zingqimba zomhlabathi kufanele zixhunywe ndawonye endaweni ethile ebhodini ngebhuloho noma indawo yokuxhuma.Ngakho-ke, amaphuzu okuxhumana kufanele asatshalaliswe ngokulinganayo kuzo zonke izingqimba ezihlukanisiwe zaphansi.Ekugcineni, kuvame ukuba nendawo yokuxhuma ku-PCB eba indawo engcono kakhulu yokubuyisela okwamanje ukuze kudlule ngaphandle kokubangela ukuwohloka ekusebenzeni.Leli phuzu lokuxhuma ngokuvamile litholakala eduze noma ngaphansi kwesiguquli.
Lapho uklama izendlalelo zokunikezwa kwamandla, sebenzisa yonke imikhondo yethusi etholakalayo yalezi zendlalelo.Uma kungenzeka, ungavumeli lezi zendlalelo ukuthi zabelane ngokuqondanisa, njengoba ukuqondanisa okwengeziwe kanye ne-vias kungalimaza ngokushesha isendlalelo sokuhlinzeka amandla ngokusihlukanisa sibe izingcezu ezincane.Isendlalelo samandla agqagqene esiwumphumela singaminyanisa izindlela zamanje lapho zidingeka khona kakhulu, okuyizikhonkwane zamandla zesiguquli.Ukucindezela i-current phakathi kwe-vias nokuqondanisa kuphakamisa ukumelana, okubangela ukwehla kwe-voltage kancane ezikhonweni zamandla zesiguquli.
Okokugcina, ukubekwa kwesendlalelo sokuhlinzekwa kwamandla kubalulekile.Ungalokothi ubeke isendlalelo samandla edijithali esinomsindo phezu kwesendlalelo samandla we-analog, noma lezi ezimbili zisengase zibhangqe nakuba zikuzendlalelo ezihlukene.Ukuze unciphise ubungozi bokuwohloka kokusebenza kwesistimu, idizayini kufanele ihlukanise lezi zinhlobo zezendlalelo kunokuba zinqwabelane ndawonye noma nini lapho kunokwenzeka.
Ingabe idizayini ye-PCB's power delivery system (PDS) ingashaywa indiva?
Umgomo wokuklama we-PDS ukunciphisa i-voltage ripple ekhiqizwa ukuphendula isidingo samanje sokuphakelwa kwamandla.Wonke amasekhethi adinga amanje, amanye anesidingo esikhulu kanti amanye adinga ukuthi isimanje sihlinzekwe ngenani elisheshayo.Ukusebenzisa amandla okuvimbeleka aphansi ahlukaniswe ngokugcwele noma ungqimba lomhlabathi kanye ne-PCB lamination enhle kunciphisa i-voltage ripple ngenxa yesidingo samanje sesekhethi.Isibonelo, uma idizayini yakhelwe ukushintshwa kwamanje kwe-1A futhi i-impedance ye-PDS ingu-10mΩ, ubuningi be-voltage ripple ngu-10mV.
Okokuqala, isakhiwo sesitaki se-PCB kufanele sakhelwe ukusekela izendlalelo ezinkulu zamandla.Isibonelo, isitaki esinezendlalelo eziyisithupha singaqukatha isendlalelo sesignali esiphezulu, isendlalelo esingaphansi sokuqala, isendlalelo samandla sokuqala, isendlalelo samandla sesibili, isendlalelo sesibili somhlaba, kanye nesiginali engezansi.Isendlalelo sokuqala somhlaba kanye nosendlalelo sokuqala sokuphakelwa kwamandla kunikezwa ukuze kusondelene esakhiweni esistakiwe, futhi lezi zendlalelo ezimbili zihlukaniswe ngamamitha angu-2 ukuya kwangu-3 ukuze zakhe amandla ongqimba angaphakathi.Inzuzo enkulu yale capacitor ukuthi imahhala futhi idinga ukucaciswa kuphela kumanothi okukhiqiza we-PCB.Uma ungqimba lokunikezela kwamandla kumele luhlukaniswe futhi kukhona amareyili kagesi e-VDD amaningi kusendlalelo esifanayo, kufanele kusetshenziswe isendlalelo esikhulu kunazo zonke sokuphakelwa kwamandla.Ungashiyi izimbobo ezingenalutho, kodwa futhi unake izifunda ezibucayi.Lokhu kuzokhulisa amandla aleso sendlalelo se-VDD.Uma umklamo uvumela ukuba khona kwezingqimba ezengeziwe, izingqimba ezimbili ezengeziwe zokubeka phansi kufanele zibekwe phakathi kwezingqimba zokuqala zokunikezwa kwamandla kagesi.Endabeni yesikhala esifanayo esiyinhloko sama-2 kuya ku-3 mils, amandla emvelo wesakhiwo esine-laminated sizophindwa kabili ngalesi sikhathi.
Ukuze uthole i-PCB lamination ekahle, ama-decoupling capacitor kufanele asetshenziswe lapho kuqalwa khona ungqimba lokuphakela amandla kanye naseduze kwe-DUT, okuzoqinisekisa ukuthi i-PDS impedance iphansi kulo lonke uhla lwamafrikhwensi.Ukusebenzisa inombolo yama-capacitor angu-0.001µF kuya ku-100µF kuzosiza ukumboza lobu bubanzi.Akudingekile ukuba nama-capacitor yonke indawo;ukufaka ama-capacitor e-docking ngqo ngokumelene ne-DUT kuzophula yonke imithetho yokukhiqiza.Uma izinyathelo ezinzima kangaka zidingeka, isifunda sinezinye izinkinga.
Ukubaluleka Kwamaphedi Aveziwe (E-Pad)
Lesi isici esilula ukunganakwa, kodwa sibalulekile ukuze kuzuzwe ukusebenza okungcono kakhulu nokunqanyulwa kokushisa komklamo we-PCB.
Iphedi eveziwe (Iphinikhodi 0) ibhekisela kuphedi engaphansi kwama-IC amaningi esimanje anesivinini esiphezulu, futhi iwuxhumano olubalulekile lapho konke ukusekela phansi kwangaphakathi kwe-chip kuxhunywe endaweni emaphakathi ngaphansi kwedivayisi.Ukuba khona kwephedi eveziwe kuvumela abaguquli abaningi nama-amplifiers ukuqeda isidingo sephini lomhlaba.Isihluthulelo siwukwenza uxhumano lukagesi oluzinzile noluthembekile kanye noxhumano olushisayo lapho unamathisela leli phedi ku-PCB, ngaphandle kwalokho isistimu ingalimala kakhulu.
Izixhumi ezisebenza kahle zikagesi nezishisayo zamaphedi avuliwe zingazuzwa ngokulandela izinyathelo ezintathu.Okokuqala, lapho kungenzeka khona, amaphedi adaluliwe kufanele aphindaphindwe kusendlalelo ngasinye se-PCB, esizohlinzeka ngoxhumano olushubile olushisayo kuwo wonke umhlaba futhi ngaleyo ndlela kuqedwe ukushisa ngokushesha, okubaluleke kakhulu kumadivayisi anamandla aphezulu.Ohlangothini lukagesi, lokhu kuzohlinzeka ngoxhumano oluhle lwe-equipotential kuzo zonke izingqimba zomhlabathi.Uma uphindaphinda amaphedi avele onqenqemeni olungezansi, angasetshenziswa njengendawo yokuhlukanisa umhlaba kanye nendawo yokufaka osinki bokushisa.
Okulandelayo, hlukanisa amaphedi adaluliwe abe yizigaba eziningi ezifanayo.Umumo webhodi lokuhlola ungcono kakhulu futhi ungafinyelelwa ngamagridi awela isikrini noma imaski ye-solder.Ngesikhathi sokuhlanganiswa kwe-reflow, akunakwenzeka ukucacisa ukuthi i-solder paste igeleza kanjani ukuze kutholakale uxhumano phakathi kwedivayisi ne-PCB, ngakho-ke uxhumano lungase lube khona kodwa lusatshalaliswe ngokungalingani, noma okubi nakakhulu, uxhumano luncane futhi lutholakala ekhoneni.Ukuhlukanisa iphedi eliveziwe libe izingxenye ezincane kuvumela indawo ngayinye ukuthi ibe nendawo yokuxhuma, ngaleyo ndlela kuqinisekisa ukwethembeka, ukuxhumana okulinganayo phakathi kwedivayisi ne-PCB.
Okokugcina, kufanele kuqinisekiswe ukuthi isigaba ngasinye sinokuxhuma kwe-over-hole emhlabathini.Izindawo ngokuvamile zinkulu ngokwanele ukubamba ama-via amaningi.Ngaphambi kokuhlanganisa, qiniseka ukuthi ugcwalisa i-vias ngayinye nge-solder paste noma i-epoxy.Lesi sinyathelo sibalulekile ukuze uqinisekise ukuthi unamathisele we-pad solder oveziwe awugelezi ubuyele emigodini ye-vias, okunganciphisa amathuba okuxhumana okufanele.
Inkinga yokuxhumanisa phakathi kwezingqimba ze-PCB
Ekwakhiweni kwe-PCB, izintambo zesakhiwo kwezinye iziguquli ezinesivinini esikhulu nakanjani zizoba nosendlalelo esisodwa sesekethe esihlanganiswe nesinye.Kwezinye izimo, isendlalelo se-analogi esibucayi (amandla, umhlabathi, noma isignali) singase sibe ngaphezu ngokuqondile kwesendlalelo sedijithali esinomsindo omkhulu.Abaklami abaningi bacabanga ukuthi lokhu akunamsebenzi ngoba lezi zendlalelo zitholakala kuzindlalelo ezihlukene.Ingabe kunjalo?Ake sibheke ukuhlolwa okulula.
Khetha eyodwa yezendlalelo eziseduze bese ujova isignali kulelo zinga, bese, uxhuma izendlalelo eziphambanayo kumshini wokuhlaziya we-spectrum.Njengoba ubona, kunezimpawu eziningi kakhulu ezihlanganiswe nongqimba oluseduze.Noma kunesikhala se-40 mils, kunomuzwa wokuthi izingqimba eziseduze zisakha amandla, ukuze kwezinye imvamisa isignali isazohlanganiswa ukusuka kungqimba olulodwa kuya kwesinye.
Uma kucatshangwa ukuthi ingxenye yedijithali enomsindo ophezulu kusendlalelo inesiginali engu-1V evela kuswishi yesivinini esikhulu, isendlalelo esingashayelwanga sizobona isignali engu-1mV ehlanganiswe nesendlalelo esishayelwayo lapho ukuhlukaniswa phakathi kwezingqimba kungu-60dB.Ku-12-bit analog-to-digital converter (ADC) ene-2Vp-p esilinganisweni esigcwele, lokhu kusho 2LSB (okungenani ibhithi elibalulekile) lokuhlangana.Ohlelweni olunikeziwe, lokhu kungase kungabi inkinga, kodwa kufanele kuqashelwe ukuthi uma ukulungiswa kunyuswa kusuka ku-12 kuya ku-14 bits, ukuzwela kukhula nge-factor of four futhi ngaleyo ndlela iphutha likhuphukela ku-8LSB.
Ukuziba ukuhlangana kwendiza/ungqimba oluphambanayo kungase kubangele ukwakheka kwesistimu ukuthi kuhluleke, noma kwenze umklamo ube buthaka, kodwa umuntu kufanele ahlale eqaphile, njengoba kungase kube nokuhlangana okwengeziwe phakathi kwezingqimba ezimbili kunalokho umuntu angase akulindele.
Lokhu kufanele kuqashelwe lapho ukuhlangana komsindo okungamanga kutholakala ngaphakathi kwe-spectrum eqondiwe.Ngezinye izikhathi izintambo zesakhiwo zingaholela kumasignali angahlosiwe noma ungqimba oluphambanayo kuzendlalelo ezahlukene.Gcina lokhu engqondweni lapho ususa iphutha kumasistimu azwelayo: inkinga ingase ilele kusendlalelo esingezansi.
Isihloko sithathwe kunethiwekhi, uma kukhona ukwephulwa komthetho, sicela uthinte ukuze ususe, ngiyabonga!
Isikhathi sokuthumela: Apr-27-2022