Isibalo sabaklami bedijithali kanye nochwepheshe bokuklama ibhodi lesifunda sedijithali emkhakheni wobunjiniyela sikhula njalo, okubonisa ukuthuthuka komkhakha. Nakuba ukugcizelelwa komklamo wedijithali kulethe intuthuko enkulu emikhiqizweni ye-elekthronikhi, isekhona, futhi kuyohlale kunemiklamo ethile yesekethe esebenzisana ne-analog noma indawo yangempela. Amasu okufaka izintambo emkhakheni we-analog kanye nedijithali anokufana okuthile, kodwa uma ufuna ukuthola imiphumela engcono, ngenxa yamasu awo okufaka izintambo ahlukene, ukwakheka kwezintambo zesifunda esilula akusesona isisombululo esifanele.

Lesi sihloko sidingida ukufana okuyisisekelo nomehluko phakathi kwezintambo ze-analog nedijithali mayelana nama-bypass capacitor, izinto zikagesi, ukwakheka komhlabathi, amaphutha kagesi, nokuphazanyiswa kukagesi kagesi (EMI) okubangelwa izintambo ze-PCB.

Isibalo sabaklami bedijithali kanye nochwepheshe bokuklama ibhodi lesifunda sedijithali emkhakheni wobunjiniyela sikhula njalo, okubonisa ukuthuthuka komkhakha. Nakuba ukugcizelelwa komklamo wedijithali kulethe intuthuko enkulu emikhiqizweni ye-elekthronikhi, isekhona, futhi kuyohlale kunemiklamo ethile yesekethe esebenzisana ne-analog noma indawo yangempela. Amasu okufaka izintambo emkhakheni we-analog kanye nedijithali anokufana okuthile, kodwa uma ufuna ukuthola imiphumela engcono, ngenxa yamasu awo okufaka izintambo ahlukene, ukwakheka kwezintambo zesifunda esilula akusesona isisombululo esifanele.

Lesi sihloko sidingida ukufana okuyisisekelo nomehluko phakathi kwezintambo ze-analog nedijithali mayelana nama-bypass capacitor, izinto zikagesi, ukwakheka komhlabathi, amaphutha kagesi, nokuphazanyiswa kukagesi kagesi (EMI) okubangelwa izintambo ze-PCB.

Ukwengeza ama-bypass noma ama-decoupling capacitor ebhodini lesifunda kanye nendawo yalawa ma-capacitor ebhodini kuwumqondo ojwayelekile wemiklamo yedijithali neye-analog. Kodwa ngokuthakazelisayo, izizathu zihlukile.

Ekwakhiweni kwezintambo ze-analog, ama-bypass capacitor ngokuvamile asetshenziselwa ukudlula amasignali amafrikhwensi aphezulu ekunikezeni amandla. Uma ama-bypass capacitor engangeziwe, lezi zimpawu zemvamisa ephezulu zingase zifake ama-analog chips azwelayo ngezikhonkwane zokuphakela amandla. Ngokuvamile, imvamisa yalezi zimpawu zefrikhwensi ephezulu idlula ikhono lemishini ye-analog ukucindezela amasignali amaza aphezulu. Uma i-bypass capacitor ingasetshenziswa kumjikelezo we-analog, umsindo ungasethulwa endleleni yesignali, futhi ezimweni ezimbi kakhulu, ungase ubangele ngisho nokudlidliza.

Ekwakhiweni kwe-analog nedijithali ye-PCB, ama-bypass noma ama-decoupling capacitor (0.1uF) kufanele abekwe eduze kwedivayisi ngangokunokwenzeka. I-capacitor yokukhipha amandla kagesi (10uF) kufanele ibekwe emnyango wentambo yamandla webhodi lesekethe. Kuzo zonke izimo, izikhonkwane zalawa ma-capacitor kufanele zibe mfushane.

Ebhodini lesifunda kuMfanekiso 2, imizila ehlukene isetshenziselwa ukuhambisa amandla nezintambo eziphansi. Ngenxa yalokhu kubambisana okungalungile, izingxenye ze-elekthronikhi namasekethe ebhodi lesifunda maningi amathuba okuba zibe ngaphansi kokuphazamiseka kazibuthe kagesi.

Ephaneli elilodwa loMfanekiso 3, izintambo zamandla kanye nephansi ezingxenyeni ebhodini lesifunda ziseduze komunye nomunye. Isilinganiso esifanayo sentambo yamandla kanye nentambo yaphansi kuleli bhodi lesifunda kufanelekile njengoba kukhonjisiwe kuMfanekiso 2. Amathuba ezingxenye ze-elekthronikhi namasekhethi ebhodini lesifunda angaphansi kokuphazanyiswa yi-electromagnetic interference (EMI) ancishiswa izikhathi ezingu-679/12.8 noma izikhathi ezingaba ngu-54.
　　
Kumadivayisi edijithali afana nezilawuli namaphrosesa, ama-decoupling capacitor nawo ayadingeka, kodwa ngezizathu ezahlukene. Umsebenzi owodwa walawa ma-capacitor ukusebenza njengebhange lokushaja “elincane”.

Kumasekhethi edijithali, inani elikhulu lamanje liyadingeka ukwenza ukushintsha kwesimo sesango. Njengoba ukushintsha imisinga yesikhashana kukhiqizwa ku-chip ngesikhathi sokushintsha nokugeleza ebhodini lesifunda, kunenzuzo ukuba nezindleko ezengeziwe "zesipele". Uma kungekho ukushaja okwanele lapho wenza isenzo sokushintsha, i-voltage yokunikezwa kwamandla izoshintsha kakhulu. Ukushintsha kwamandla kagesi amaningi kakhulu kuzobangela izinga lesignali yedijithali ukuthi lingene esimweni esingaqinisekile, futhi kungase kubangele umshini wombuso kudivayisi yedijithali ukuthi isebenze ngokungalungile.

I-switching current egeleza ngomkhondo webhodi lesifunda izobangela ukuthi i-voltage ishintshe, futhi umkhondo webhodi lesifunda une-parasitic inductance. Ifomula elandelayo ingasetshenziswa ukubala ukushintsha kwamandla kagesi: V = LdI/dt. Phakathi kwazo: V = ushintsho lwe-voltage, L = ibhodi lesifunda lokulandelela inductance, dI = ushintsho lwamanje ngokusebenzisa umkhondo, dt = isikhathi sokushintsha samanje.
　　
Ngakho-ke, ngenxa yezizathu eziningi, kungcono ukusebenzisa i-bypass (noma i-decoupling) capacitor ekunikezeni amandla noma izikhonkwane zokunikezwa kwamandla zamadivayisi asebenzayo.

Intambo yamandla nentambo yaphansi kufanele kuhanjiswe ndawonye

Ukuma kwentambo yamandla kanye nentambo yaphansi kuhambisana kahle ukuze kuncishiswe ukuthikamezeka kwe-electromagnetic. Uma intambo yamandla kanye nentambo yaphansi kungafaniswa kahle, iluphu yesistimu izoklanywa futhi nomsindo uzokwenziwa.

Isibonelo sedizayini ye-PCB lapho intambo yamandla nentambo yaphansi ingafaniswa kahle iboniswa kuMdwebo 2. Kuleli bhodi lesekhethi, indawo yeluphu eklanyelwe ingu-697cm². Ngokusebenzisa indlela ekhonjiswe kuMfanekiso 3, amathuba okuba nomsindo okhipha imisebe ebhodini lesifunda noma avale i-voltage eheha iluphu kungancishiswa kakhulu.

Umehluko phakathi kwamasu ezintambo ze-analog nedijithali

▍Indiza ephansi iyinkinga

Ulwazi oluyisisekelo lwezintambo zebhodi lesifunda lusebenza kuzo zombili izifunda ze-analog nedijithali. Umthetho oyisisekelo uwukusebenzisa indiza yaphansi engaphazamiseki. Lo mqondo ojwayelekile wehlisa umphumela we-dI/dt (ushintsho lwamanje nesikhathi) kumasekhethi edijithali, okushintsha amandla aphansi futhi abangele umsindo ukungena kumasekhethi e-analog.

Izindlela zokufaka izintambo zamasekhethi edijithali nawe-analog ziyafana, ngaphandle kokukodwa. Kumasekhethi e-analog, kunelinye iphuzu okufanele uliqaphele, okungukuthi, gcina imigqa yesignali yedijithali kanye nezihibe endizeni yaphansi kude kakhulu neziyingi ze-analog ngangokunokwenzeka. Lokhu kungafinyelelwa ngokuxhuma indiza ye-analog yomhlabathi ekuxhumaneni komhlabathi wesistimu ngokwehlukana, noma ukubeka isifunda se-analog ekugcineni kwebhodi lesifunda, okuwukuphela komugqa. Lokhu kwenzelwa ukugcina ukuphazamiseka kwangaphandle endleleni yesignali kube kuncane.

Asikho isidingo sokwenza lokhu kumasekhethi edijithali, akwazi ukubekezelela umsindo omningi endizeni yaphansi ngaphandle kwezinkinga.

Umfanekiso wesi-4 (kwesokunxele) uhlukanisa isenzo sokushintshwa kwedijithali kumjikelezo we-analogi futhi uhlukanise izingxenye zedijithali neze-analog zesekhethi. (Kwesokudla) I-frequency ephezulu kanye nefrikhwensi ephansi kufanele ihlukaniswe ngangokunokwenzeka, futhi izingxenye zemvamisa ephezulu kufanele zibe seduze nezixhumi zebhodi lesifunda.

Umfanekiso 5 Isakhiwo sokulandela okubili okusondele ku-PCB, kulula ukwakha amandla e-parasitic. Ngenxa yobukhona balolu hlobo lwamandla, ukuguqulwa kwe-voltage okusheshayo kumkhondo owodwa kungakhiqiza isignali yamanje komunye umkhondo.

Umfanekiso 6 Uma unganaki ukubekwa kwemikhondo, imikhondo ku-PCB ingase ikhiqize inductance yomugqa kanye ne-mutual inductance. Le inductance ye-parasitic iyingozi kakhulu ekusebenzeni kwamasekhethi kufaka phakathi amasekhethi okushintsha idijithali.

▍Indawo yengxenye

Njengoba kushiwo ngenhla, kumklamo ngamunye we-PCB, ingxenye yomsindo wesifunda kanye nengxenye “ethule” (ingxenye engeyona yomsindo) kufanele ihlukaniswe. Ngokuvamile, amasekhethi edijithali “acebile” ngomsindo futhi awawuzweli umsindo (ngoba amasekhethi edijithali anokubekezelela okukhulu komsindo kagesi); ngokuphambene nalokho, ukubekezelelana komsindo we-voltage wamasekhethi e-analog kuncane kakhulu.

Kulawa amabili, amasekhethi e-analog azwela kakhulu ekushintsheni umsindo. Kuzintambo zesistimu yesignali exubile, lezi zifunda ezimbili kufanele zihlukaniswe, njengoba kuboniswe kuMfanekiso 4.
　　
▍Izingxenye zeParasitic ezikhiqizwe idizayini ye-PCB

Izinto ezimbili eziyisisekelo ze-parasitic ezingase zidale izinkinga zakheka kalula ekwakhiweni kwe-PCB: i-parasitic capacitance kanye ne-parasitic inductance.

Lapho uklama ibhodi lesifunda, ukubeka imikhondo emibili eduze komunye nomunye kuzokhiqiza amandla e-parasitic. Ungenza lokhu: Ezingqimbeni ezimbili ezihlukene, beka umkhondo owodwa phezu komunye; noma kungqimba olufanayo, beka umkhondo owodwa eduze komunye, njengoba kuboniswe kuMfanekiso 5.
　　
Kulokhu kulungiselelwa okubili kokulandela umkhondo, izinguquko ku-voltage ngokuhamba kwesikhathi (dV/dt) kumkhondo owodwa zingase zibangele amandla kwenye ithrekhi. Uma enye i-trace i-impedance ephezulu, yamanje ekhiqizwa inkambu kagesi izoguqulwa ibe yi-voltage.
　　
Ama-voltage asheshayo adlulayo avame ukwenzeka ngasohlangothini lwedijithali lomklamo wesignali ye-analog. Uma ukulandelelwa okunama-voltage asheshayo adlulayo kuseduze nokulandelelwa kwe-analogi ephezulu, leli phutha lizophazamisa kakhulu ukunemba kwesekethe ye-analog. Kule ndawo, izifunda ze-analog zinezinkinga ezimbili: ukubekezelelana kwabo komsindo kuphansi kakhulu kunamasekhethi edijithali; futhi iminonjana ephezulu ye-impedance ivame kakhulu.
　　
Ukusebenzisa enye yalezi zindlela ezimbili ezilandelayo kunganciphisa lesi simo. Indlela esetshenziswa kakhulu ukushintsha usayizi phakathi kokulandelelwa ngokuya ngesibalo se-capacitance. Usayizi osebenza kahle kakhulu ongashintshwa yibanga phakathi kwemikhondo emibili. Kufanele kuqashelwe ukuthi okuguquguqukayo okungu-d kuyidinominayitha yesibalo somthamo. Njengoba i-d ikhula, ukusabela kwe-capacitive kuzokwehla. Okunye okuguquguqukayo okungashintshwa ubude bemigqa emibili. Kulokhu, ubude L buyancipha, futhi ukusabela kwe-capacitive phakathi kwamathrekhi amabili nakho kuzokwehla.
　　
Enye indlela ukubeka ucingo oluphansi phakathi kwalezi zindlela ezimbili. Intambo yaphansi inamandla aphansi, futhi ukwengeza omunye umkhondo ofana nalona kuzowenza buthaka indawo kagesi yokuphazamiseka, njengoba kuboniswe kuMfanekiso 5.
　　
Umgomo we-parasitic inductance ebhodini lesifunda ufana ne-parasitic capacitance. Kuphinde futhi kubekwe imikhondo emibili. Ezingqimbeni ezimbili ezihlukene, beka umkhondo owodwa phezu komunye; noma kungqimba olufanayo, beka umkhondo owodwa eduze komunye, njengoba kuboniswe kuMfanekiso 6.

Kulokhu kulungiselelwa kwezintambo ezimbili, ushintsho lwamanje (dI/dt) lomkhondo ngokuhamba kwesikhathi, ngenxa yokungena kwalo mkhondo, luzokhiqiza i-voltage ngomkhondo ofanayo; futhi ngenxa yobukhona be-mutual inductance, izoba I-proportional current ikhiqizwa ngakolunye umkhondo. Uma ushintsho lwe-voltage kumkhondo wokuqala lukhulu ngokwanele, ukuphazamiseka kungase kunciphise ukubekezelela i-voltage yesifunda sedijithali futhi kubangele amaphutha. Lesi simo asenzeki kuphela kumasekhethi edijithali, kodwa lesi simo sivame kakhulu kumasekhethi edijithali ngenxa yokushintshashintsha kwemisinga emikhulu esheshayo kumasekhethi edijithali.
　　
Ukuze uqede umsindo ongaba khona emithonjeni yokuphazamiseka kazibuthe, kungcono ukuhlukanisa imigqa ye-analogi “ethule” nezimbobo ze-I/O ezinomsindo. Ukuze uzame ukufeza amandla aphansi-impedance kanye nenethiwekhi yomhlabathi, ukungeniswa kwezintambo ze-digital circuit kufanele kuncishiswe, futhi ukuhlanganisa i-capacitive yama-analog circuits kufanele kuncishiswe.
　　
03

Isiphetho

Ngemva kokunqunywa kwebanga ledijithali nele-analogi, ukuqondiswa ngokucophelela kubalulekile ku-PCB ephumelelayo. Isu lezintambo ngokuvamile lethulwa kuwo wonke umuntu njengomthetho wesithupha, ngoba kunzima ukuhlola impumelelo yokugcina yomkhiqizo endaweni yaselabhorethri. Ngakho-ke, naphezu kokufana kwamasu okufaka izintambo esekethe yedijithali ne-analog, umehluko kumasu abo okufaka izintambo kufanele uqashelwe futhi uthathwe ngokungathí sina.