Abstract: Uyilo lwesekethe ye-mix-signal circuit PCB inzima kakhulu. Uyilo kunye nocingo lwamacandelo kunye nokusetyenzwa kokunikezelwa kwamandla kunye nocingo lomhlaba kuya kuchaphazela ngokuthe ngqo ukusebenza kwesekethe kunye nokusebenza kokuhambelana kwe-electromagnetic. Uyilo lwesahlulelo somhlaba kunye namandla afakwe kweli nqaku lunokwandisa ukusebenza kweesekethe ezixubileyo zesignali.

Ukunciphisa njani ukuphazamiseka phakathi komqondiso wedijithali kunye nomqondiso we-analog? Ngaphambi kokuyila, kufuneka siqonde imigaqo emibini esisiseko yokuhambelana kwe-electromagnetic (EMC): Umgaqo wokuqala kukunciphisa indawo yelophu yangoku; umgaqo wesibini kukuba inkqubo isebenzisa indawo enye kuphela yereferensi. Ngokuchasene noko, ukuba inkqubo ineendiza ezimbini zokubhekisela, kunokwenzeka ukwenza i-antenna ye-dipole (Qaphela: ubungakanani bemitha ye-antenna encinci ye-dipole ilingana nobude bomgca, ubungakanani bokuhamba ngoku kunye nokuphindaphinda); kwaye ukuba isignali ayinakudlula kangangoko kunokwenzeka Ukubuya kweluphu encinci kunokwenza i-eriyali yelophu enkulu (Qaphela: ubungakanani bemitha ye-eriyali encinci yeluphu bulungelelaniswa nendawo yeluphu, yangoku equkuqela kwiluphu, kunye nesikwere. yefrikhwensi). Gwema ezi meko zimbini kangangoko kunokwenzeka kuyilo.

Kucetyiswa ukuba uhlukanise umhlaba wedijithali kunye nomhlaba we-analog kwibhodi yesekethe edibeneyo, ukwenzela ukuba ukuhlukaniswa phakathi komhlaba wedijithali kunye nomhlaba we-analog kunokufezekiswa. Nangona le ndlela inokwenzeka, zininzi iingxaki ezinokubakho, ngakumbi kwiinkqubo ezinkulu ezintsonkothileyo. Eyona ngxaki ibaluleke kakhulu kukuba ayinakugqithiswa kwisithuba sokwahlulahlula. Nje ukuba umsantsa wokwahlula udluliselwe, imitha ye-electromagnetic kunye ne-signal crosstalk iya kwanda kakhulu. Eyona ngxaki ixhaphakileyo kuyilo lwePCB kukuba umgca wesignali uwela umhlaba owahluliweyo okanye unikezelo lwamandla kwaye luvelise iingxaki ze-EMI.

Ulufumana njani ulwahlulo loyilo lwe-PCB exubeneyo

Njengoko kuboniswe kwi-Figure 1, sisebenzisa indlela yokwahlula ekhankanywe ngasentla, kwaye umgca wesignali uwela i-gap phakathi kwezizathu ezimbini. Ithini indlela yokubuya yesignali yangoku? Ukucinga ukuba izizathu ezibini ezihlulwe zidibene kunye kwindawo ethile (ngokuqhelekileyo uxhulumaniso lwenqaku elilodwa kwindawo ethile), kulo mzekelo, umhlaba okhoyo uya kwenza i-loop enkulu. I-high-frequency current equkuqela kwi-loop enkulu yenza i-radiation kunye ne-inductance yomhlaba ophezulu. Ukuba i-analog yangoku yezinga eliphantsi lihamba nge-loop enkulu, i-current iphazamiseka lula ngezibonakaliso zangaphandle. Eyona nto imbi kakhulu kukuba xa imihlaba eyahluliweyo idityaniswe ndawonye kunikezelo lwamandla, i-loop yangoku enkulu kakhulu iya kwenziwa. Ukongezelela, umhlaba we-analog kunye nomhlaba wedijithali uxhunywe ngocingo olude ukwenza i-antenna ye-dipole.

Ukuqonda indlela kunye nendlela yokubuyela ngoku emhlabeni ngundoqo wokuphucula ibhodi yebhodi yesekethe edibeneyo. Iinjineli ezininzi zokuyila ziqwalasela kuphela apho umqondiso wangoku uhamba khona, kwaye ungayihoyi indlela ethile yangoku. Ukuba umaleko womhlaba kufuneka uhlukaniswe, kwaye i-wiring kufuneka ihanjiswe kwi-gap phakathi kwezahlulo, uxhulumaniso lwendawo enye lunokwenziwa phakathi kwezizathu ezahlulahlulayo ukwenza ibhuloho yokudibanisa phakathi kweendawo ezimbini, kwaye emva koko i-wiring ngokusebenzisa ibhuloho yokudibanisa. . Ngale ndlela, indlela yokubuyisela ngoku ngokuthe ngqo inokubonelelwa phantsi komgca wesignali ngamnye, ukwenzela ukuba indawo ye-loop yenziwe incinci.

Ukusetyenziswa kwezixhobo zokuhlukanisa i-optical isolation okanye i-transformers inokuphinda ifezekise isignali kwi-gap ye-segmentation. Ngowokuqala, ngumqondiso we-optical owela i-gap ye-segmentation; kwimeko ye-transformer, yintsimi yamagnetic ewela i-gap ye-segmentation. Enye indlela enokwenzeka kukusebenzisa imiqondiso eyahlukileyo: isiginali ingena isuka komnye umgca kwaye ibuya isuka komnye umgca wesignali. Kule meko, umhlaba awufunwa njengendlela yokubuya.

Ukuphonononga ngokunzulu ukuphazamiseka kweempawu zedijithali kwiimpawu ze-analog, kufuneka siqale siqonde iimpawu ze-high-frequency currents. Kwimisinga ye-high-frequency currents, soloko ukhetha umendo kunye ne-impedance encinci (i-inductance ephantsi) kwaye ngokuthe ngqo ngaphantsi kwesignali, ngoko i-return current iya kuhamba ngomgca wesiphaluka osondeleyo, kungakhathaliseki ukuba umgca osondeleyo ngumaleko wamandla okanye umgangatho womhlaba. .

Kumsebenzi wokwenyani, kudla ngokutyekela ekusebenziseni umhlaba odityanisiweyo, kunye nokwahlulahlula iPCB kwinxalenye ye-analog kunye nenxalenye yedijithali. Isiginali ye-analog ihanjiswa kwindawo ye-analog yazo zonke iileyiti zebhodi yesekethe, kwaye isiginali yedijithali ihanjiswa kwindawo yesekethe yedijithali. Kule meko, i-digital signal return current ayizukungena kumhlaba wesignali ye-analog.

Kuphela xa isignali yedijithali ifakwe kwi-analog inxalenye yebhodi yesiphaluka okanye isignali ye-analog ifakwe kwi-digital inxalenye yebhodi yesekethe, ukuphazamiseka kwesignali yedijithali kwi-analog signal kuya kubonakala. Olu hlobo lwengxaki alwenzeki ngenxa yokuba akukho mhlaba owahluliweyo, isizathu sokwenene yi-wiring engafanelekanga yesiginali yedijithali.

Uyilo lwe-PCB lwamkela umhlaba odibeneyo, ngokusebenzisa isekethe yedijithali kunye nokwahlulahlula kwesekethe ye-analog kunye nocingo olufanelekileyo lomqondiso, ngokuqhelekileyo lunokusombulula ezinye iingxaki ezinzima zokubeka kunye neengcingo, kwaye kwangaxeshanye, aziyi kubangela iingxaki ezinokuthi zibangelwa kukwahlulwa komhlaba. Kule meko, ukucwangciswa kunye nokwahlula kwamacandelo kuba ngundoqo ekunqumeni i-pros and cons of the design. Ukuba i-layout inengqiqo, i-digital ground current iya kunqunyulwa kwi-digital part yebhodi yesiphaluka kwaye ayiyi kuphazamisa isignali ye-analog. I-wiring enjalo kufuneka ihlolwe ngokucophelela kwaye iqinisekiswe ukuqinisekisa ukuba imithetho yocingo ithotyelwe nge-100%. Ngaphandle koko, umzila ongafanelekanga womgca wesignali uya kutshabalalisa ngokupheleleyo ibhodi yesekethe elunge kakhulu.

Xa udibanisa umhlaba we-analog kunye nezikhonkwane zomhlaba zedijithali ze-A / D converter kunye, abaninzi abavelisi be-A / D abaguquli bangacebisa: Xhuma i-AGND kunye ne-DGND izikhonkwane kumhlaba ofanayo ophantsi we-impedance ngokusebenzisa isikhokelo esifutshane. (Qaphela: Ngenxa yokuba i-chips ezininzi ze-A / D ze-converter azixhumi umhlaba we-analog kunye nomhlaba wedijithali kunye, i-analog kunye nomhlaba wedijithali kufuneka udibaniswe ngokusebenzisa izikhonkwane zangaphandle.) Nayiphi na i-impedance yangaphandle exhunywe kwi-DGND iya kudlula i-parasitic capacitance. Ingxolo eyongezelelekileyo yedijithali idityaniswe kwiisekethe ze-analog ngaphakathi kwe-IC. Ngokwale ngcebiso, kufuneka udibanise i-AGND kunye ne-DGND izikhonkwane ze-A / D converter kumhlaba we-analog, kodwa le ndlela iya kubangela iingxaki ezifana nokuba i-terminal yomhlaba ye-digital signal decoupling capacitor kufuneka idibaniswe kumhlaba we-analog. okanye umhlaba wedijithali.

Ulufumana njani ulwahlulo loyilo lwe-PCB exubeneyo

Ukuba inkqubo inomguquli omnye kuphela we-A/D, ezi ngxaki zingasentla zinokusonjululwa ngokulula. Njengoko kuboniswe kwi-Figure 3, yahlula umhlaba, kwaye udibanise umhlaba we-analog kunye nomhlaba wedijithali kunye phantsi kwe-A / D converter. Xa wamkela le ndlela, kuyimfuneko ukuqinisekisa ukuba ububanzi bebhuloho yokudibanisa phakathi kwezizathu ezimbini bufana nobubanzi be-IC, kwaye nawuphi na umgca wesignali awukwazi ukuwela i-gap yokwahlula.

Ukuba kukho abaguquleli abaninzi be-A/D kwinkqubo, umzekelo, indlela yokudibanisa i-10 A/D converters? Ukuba umhlaba we-analog kunye nomhlaba wedijithali udibene kunye phantsi kwe-converter nganye ye-A / D, uxhulumaniso lwamanqaku amaninzi luyenziwa, kwaye ukuhlukaniswa phakathi komhlaba we-analog kunye nomhlaba wedijithali akukho nto. Ukuba awudibanisi ngale ndlela, iphula iimfuno zomenzi.