PCB Uyilo lwesekethe yophawu oluxubileyo lunzima kakhulu. Uyilo kunye nocingo lwamacandelo kunye nokusetyenzwa kokunikezelwa kwamandla kunye nocingo lomhlaba kuya kuchaphazela ngokuthe ngqo ukusebenza kwesekethe kunye nokusebenza kokuhambelana kwe-electromagnetic. Uyilo lokwahlula komhlaba kunye nonikezelo lwamandla olufakwe kweli phepha lunokwandisa ukusebenza kweesekethe ezixubileyo zesignali.

Indlela yokunciphisa ukuphazamiseka phakathi kwedijithali kunye neempawu ze-analog? Imigaqo emibini esisiseko yokuhambelana kwe-electromagnetic (EMC) kufuneka iqondwe ngaphambi koyilo: umgaqo wokuqala kukunciphisa indawo ye-loop yangoku; Umgaqo wesibini kukuba inkqubo isebenzisa inqwelomoya enye kuphela. Ngokuchasene noko, ukuba inkqubo ineendiza ezimbini zokubhekisela, kunokwenzeka ukwenza i-antenna ye-dipole (qaphela: i-radiation ye-antenna encinci ye-dipole ilingana nobude bomgca, ubungakanani bokuhamba ngoku, kunye nokuphindaphinda). Ukuba umqondiso awubuyi ngeyona loop incinci kunokwenzeka, i-eriyali enkulu ejikelezayo inokwakheka. Ziphephe zombini kuyilo lwakho kangangoko kunokwenzeka.

Kuye kwacetyiswa ukuba uhlukanise umhlaba wedijithali kunye nomhlaba we-analog kwibhodi yesekethe ye-mix-signal ukuphumeza ukuhlukaniswa phakathi komhlaba wedijithali kunye nomhlaba we-analog. Nangona le ndlela inokwenzeka, ineengxaki ezininzi ezinokubakho, ngakumbi kwiinkqubo ezinkulu nezintsonkothileyo. Eyona ngxaki ibaluleke kakhulu kukungaweli i-wiring ye-gap, xa sele uwele i-wiring ye-gap, i-electromagnetic radiation kunye ne-signal crosstalk iya kwanda kakhulu. Eyona ngxaki ixhaphakileyo kuyilo lwe-PCB yingxaki ye-EMI ebangelwa ngumgca womqondiso owela umhlaba okanye unikezelo lwamandla.

Njengoko kuboniswe kwi-Figure 1, sisebenzisa indlela yokwahlula ngasentla, kwaye umgca wesignali ubeka i-gap phakathi kweendawo ezimbini zomhlaba, yintoni indlela yokubuya yesignali yangoku? Masithi imihlaba emibini eyohluliweyo idityaniswe kwinqanaba elithile (ngokuqhelekileyo inqaku elinye kwindawo enye), apho imeko yomhlaba iya kwenza i-loop enkulu. Umbane ophezulu ojikelezayo kwi-loop enkulu uya kuvelisa i-radiation kunye ne-inductance ephezulu. Ukuba inqanaba eliphantsi le-analog yangoku elihamba nge-loop enkulu kulula ukuphazanyiswa yimiqondiso yangaphandle. Eyona nto imbi kakhulu kukuba xa amacandelo edityaniswe kunye kumthombo wamandla, i-loop yangoku enkulu kakhulu yenziwa. Ukongezelela, i-analog kunye nomhlaba wedijithali oxhunywe ngocingo olude lwakha i-antenna ye-dipole.

Ukuqonda indlela kunye nendlela yokubuyela umva ngoku ukuya emhlabeni ngundoqo wokuphucula ibhodi yebhodi yesekethe edibeneyo. Iinjineli ezininzi zokuyila ziqwalasela kuphela apho umqondiso wangoku uhamba khona, ungayihoyi indlela ethile yangoku. Ukuba umaleko womhlaba kufuneka uhlukaniswe kwaye kufuneka uhanjiswe kwi-gap phakathi kwezahlulo, uxhulumaniso lwendawo enye lunokwenziwa phakathi kwendawo edibeneyo ukuze yenze ibhuloho yokudibanisa phakathi kwemigangatho emibini yomhlaba kwaye emva koko iqhutywe kwibhuloho yokudibanisa. Ngale ndlela, indlela yokubuyisela umva ngoku ngokuthe ngqo inokubonelelwa ngaphantsi komgca wesignali ngamnye, okukhokelela kwindawo encinci ye-loop.

Izixhobo zokujonga zodwa okanye iziguquli zingasetyenziselwa ukuqonda umqondiso wokuwela isithuba secandelo. Kweyangaphambili, sisignali ye-optical eyenza i-gap ye-segmentation. Kwimeko ye-transformer, yintsimi yamagnetic edibanisa i-gap yokwahlula. Izibonakaliso ezihlukeneyo nazo zinokwenzeka: iimpawu zihamba ukusuka kumgca omnye kwaye zibuye zivela kwelinye, apho zisetyenziswa njengeendlela zokubuyela umva ngokungeyomfuneko.

Ukuphonononga ukuphazamiseka kwesignali yedijithali kwisignali ye-analog, kufuneka siqale siqonde iimpawu ze-high frequency yangoku. I-high-frequency current isoloko ikhetha indlela ene-impedance ephantsi kakhulu (i-inductance) ngokuthe ngqo ngaphantsi kwesignali, ngoko ke umbane obuyayo uya kuhamba ngomgca wesiphaluka osondeleyo, kungakhathaliseki ukuba umgca osondeleyo ngumaleko ombane okanye umgangatho womhlaba.

Ngokwesiqhelo, kukhethwa ngokubanzi ukusebenzisa isahlulelo sePCB esifanayo sibe ngamacandelo e-analog kunye nedijithali. Iimpawu ze-analog zihanjiswa kwingingqi ye-analog yazo zonke iileya zebhodi, ngelixa iimpawu zedijithali zihanjiswa kwingingqi yesekethe yedijithali. Kule meko, i-digital signal return current ayihambi emhlabeni wesignali ye-analog.

Ukuphazamiseka kwimiqondiso yedijithali ukuya kwiimpawu ze-analog kwenzeka kuphela xa iimpawu zedijithali zihanjiswa ngaphaya okanye iimpawu ze-analog zihanjiswa kwiindawo zedijithali zebhodi yesekethe. Le ngxaki ayikho ngenxa yokungabikho kokwahlula, isizathu sokwenene yi-wiring engafanelekanga yeempawu zedijithali.

Uyilo lwePCB lusebenzisa umanyano, ngokusebenzisa isekethe yedijithali kunye nesahlulelo sesekethe ye-analog kunye nocingo olufanelekileyo lweempawu, ngokuqhelekileyo lunokusombulula ezinye zeendlela ezinzima ngakumbi kunye neengxaki zocingo, kodwa kwakhona ayinayo ingxaki enokubakho ebangelwa kukwahlulwa komhlaba. Kule meko, ukucwangciswa kunye nokwahlula kwamacandelo kuba yinto ebalulekileyo ekunqumeni umgangatho woyilo. Ukuba ibekwe ngokufanelekileyo, i-digital ground current iya kulinganiselwa kwi-digital part yebhodi kwaye ayiyi kuphazamisa isignali ye-analog. I-wiring enjalo kufuneka ihlolwe ngokucophelela kwaye ihlolwe ukuze kuqinisekiswe ukuthotyelwa kwe-100% kunye nemithetho yocingo. Ngaphandle koko, umgca wesignali ongafanelekanga uya kutshabalalisa ngokupheleleyo ibhodi yesiphaluka esihle kakhulu.

Xa udibanisa i-analog kunye nezikhonkwane zomhlaba wedijithali ze-A/D converters kunye, uninzi lwabavelisi be-A/D converter bancomela ukudibanisa i-AGND kunye ne-DGND izikhonkwane kumhlaba ofanayo ophantsi-impedance usebenzisa ezona ndlela zimfutshane (Qaphela: Ngenxa yokuba uninzi lweetshiphusi ze-A/D zoguqulo zingadibanisi i-analog kunye nomhlaba wedijithali kunye ngaphakathi, i-analog kunye nomhlaba wedijithali kufuneka ziqhagamshelwe ngezikhonkwane zangaphandle), nayiphi na i-impedance yangaphandle eqhagamshelwe kwi-DGND iya kudibanisa ingxolo yedijithali ngakumbi kwisekethe ye-analog ngaphakathi kwe-IC nge-parasitic. amandla. Ukulandela le ngcebiso, zombini i-A / D converter AGND kunye ne-DGND izikhonkwane kufuneka zixhunywe kumhlaba we-analog, kodwa le ndlela iphakamisa imibuzo efana nokuba isiphelo somhlaba we-digital signal decoupling capacitor kufuneka ixhunywe kwi-analog okanye umhlaba wedijithali.

Ukuba inkqubo inomguquli omnye kuphela we-A/D, le ngxaki ingasentla ingasonjululwa ngokulula. Njengoko kuboniswe kwi-Figure 3, umhlaba uhlukaniswe kwaye i-analog kunye ne-digital ground amacandelo axhunyiwe kunye phantsi kwe-A / D converter. Xa le ndlela yamkelwa, kuyimfuneko ukuqinisekisa ukuba ububanzi bebhulorho phakathi kweziza ezimbini bulingana nobubanzi be-IC, kwaye akukho mgca wesignali unokuwela i-gap yokwahlula.

Ukuba inkqubo inabaninzi abaguquli be-A/D, umzekelo, abaguquli be-10 A/D indlela yokudibanisa? Ukuba i-analog kunye nomhlaba wedijithali zidibaniswe phantsi kwe-converter nganye ye-A / D, i-multipoint connection iya kubangela, kwaye ukuhlukaniswa phakathi kwe-analog kunye nomhlaba wedijithali kuya kuba ngenanto. Ukuba akunjalo, waphula iimfuno zomenzi.

Eyona ndlela ilungileyo kukuqala ngeyunifomu. Njengoko kuboniswe kwi-Figure 4, umhlaba uhlukaniswe ngokulinganayo kwiingxenye ze-analog kunye nedijithali. Olu cwangciso aluhlangabezani kuphela neemfuno zabavelisi besixhobo se-IC kuxhulumaniso oluphantsi lwe-impedance ye-analog kunye nezikhonkwane zomhlaba wedijithali, kodwa zithintela iingxaki ze-EMC ezibangelwa yi-antenna ye-loop okanye i-antenna ye-dipole.

Ukuba unamathandabuzo malunga nendlela edityanisiweyo yoyilo lwePCB edityanisiweyo, ungasebenzisa indlela yokwahlulahlula umaleko womhlaba ukubeka kunye nendlela yonke ibhodi yesekethe. Kuyilo, ingqalelo kufuneka ihlawulwe ukwenza ibhodi yesekethe lula ukudibanisa kunye jumpers okanye 0 ohm resistors isithuba esingaphantsi kwe-1/2 intshi ngaphandle kumfuniselo kamva. Nika ingqalelo kwizowuni kunye neengcingo zokuqinisekisa ukuba akukho migca yesiginali yedijithali ingaphezulu kwecandelo le-analog kuzo zonke iileya kwaye akukho migca yesiginali ye-analog ingaphezulu kwecandelo ledijithali. Ngaphezu koko, akukho mgca wesignali kufuneka unqumle umsantsa osemhlabeni okanye wahlule umsantsa phakathi kwemithombo yamandla. Ukuvavanya umsebenzi webhodi kunye nokusebenza kwe-EMC, phinda uvavanye umsebenzi webhodi kunye nokusebenza kwe-EMC ngokudibanisa imigangatho emibini kunye nge-0 ohm resistor okanye jumper. Ukuthelekisa iziphumo zovavanyo, kwafunyaniswa ukuba phantse kuzo zonke iimeko, isisombululo esimanyeneyo sasiphezulu ngokumalunga nokusebenza kunye nokusebenza kwe-EMC xa kuthelekiswa nesisombululo sokwahlula.

Ngaba indlela yokwahlulwa komhlaba isasebenza?

Le ndlela ingasetyenziswa kwiimeko ezintathu: ezinye izixhobo zonyango zifuna ukuvuza okuphantsi kakhulu kwangoku phakathi kweesekethe kunye neenkqubo ezixhunyiwe kwisigulane; Imveliso yezinye izixhobo zokulawula inkqubo yoshishino inokudityaniswa kwizixhobo ezinomsindo kunye nezixhobo eziphezulu ze-electromechanical; Enye imeko kuxa UKUBEKWA kwe-PCB kuxhomekeke kwizithintelo ezithile.

Ngokuqhelekileyo kukho unikezelo lwamandla edijithali kunye ne-analog kwibhodi ye-PCB exubeneyo enokuthi kwaye kufuneka ibe nobuso bobonelelo lwamandla. Nangona kunjalo, imigca yesignali esecaleni komgangatho wokunikezelwa kwamandla ayikwazi ukuwela umsantsa phakathi kwezixhobo zombane, kwaye yonke imigca yesignali ewela i-gap kufuneka ibekwe kwinqanaba lesekethe elikufutshane nommandla omkhulu. Kwezinye iimeko, unikezelo lwamandla e-analog lunokuyilwa kunye noqhagamshelo lwePCB kunobuso obunye ukunqanda ukwahlulwa kobuso bamandla.

Uyilo lokwahlulo lwePCB yomqondiso oxutyiweyo

Uyilo oluxubeneyo lwePCB yinkqubo entsonkothileyo, inkqubo yoyilo kufuneka ithathele ingqalelo la manqaku alandelayo:

1. Yahlula i-PCB ibe ngamacandelo e-analog kunye nedijithali.

2. Uyilo lwecandelo elifanelekileyo.

3. Isiguquli se-A/D sibekwe kuzo zonke izahlulo.

4 Musa ukwahlula umhlaba. Inxalenye ye-analog kunye nenxalenye yedijithali yebhodi yesekethe ibekwe ngokufanayo.

5. Kuzo zonke iileyile zebhodi, isignali yedijithali ingahanjiswa kuphela kwindawo yedijithali yebhodi.

6. Kuzo zonke iileyile zebhodi, iimpawu ze-analog zinokuhanjiswa kuphela kwindawo ye-analog yebhodi.

7. I-analog kunye nokwahlukana kwamandla edijithali.

8. Iingcingo azifuneki zivule isithuba phakathi kweendawo zonikezelo lwamandla olwahlulwahlulwayo.

9. Imigca yomqondiso ekufuneka ivule i-gap phakathi kokunikezelwa kwamandla okuqhekeka kufuneka ibekwe kwi-wiring layer ejongene nommandla omkhulu.

10. Hlalutya eyona ndlela kunye nendlela yokuhamba komhlaba ngoku.

11. Sebenzisa imigaqo yocingo echanekileyo.