Ungawuthintela njani umphumo wokuhambisa umgca kwi Isantya esiphezulu sePCB uyilo

1. Iindlela zokucinezela ukuphazamiseka kwombane

Isisombululo esifanelekileyo kwingxaki yemfezeko yomqondiso siya kuphucula ukungqinelana kombane (EMC) webhodi yePCB. Enye yezona zibalulekileyo kukuqinisekisa ukuba ibhodi PCB has isiseko elungileyo. Uluhlu lwesiginali kunye nogaleko lomhlaba yeyona ndlela isebenzayo yoyilo oluntsonkothileyo. Ukongeza, ukunciphisa uxinano lomqondiso wolwelwangaphandle kwibhodi yesekethe ikwayindlela elungileyo yokunciphisa imitha yombane. Le ndlela inokufezekiswa ngokusebenzisa ubuchwephesha bokwakha “indawo yokwakha” itekhnoloji ye-PCB. Umaleko wommandla womphezulu ufezekiswa ngokudibanisa indibaniselwano yolwembu lobushushu kunye nee-micropores ezisetyenziselwa ukungena kwezi zahlulo kwi-PCB yenkqubo ngokubanzi. Ukuxhathisa kunye namandla okusebenza kungangcwatywa ngaphantsi komphezulu womhlaba, kwaye uxinano lomgama kwiyunithi nganye iphantse iphindwe kabini, oko ke kunciphisa umthamo wePCB. Ukuncitshiswa kwendawo ye-PCB kunefuthe elikhulu kubuchwephesha bendlela, oko kuthetha ukuba iluphu yangoku iyancitshiswa, ubude bendlela yesebe buyancitshiswa, kwaye imitha ye-electromagnetic imalunga ngokulinganayo nendawo yeluphu yangoku; At the same time, the small size characteristics mean that high-density pin packages can be used, which in turn reduces the length of the wire, thus reducing the current loop and improving emc characteristics.

2. Strictly control the cable lengths of key network cables

If the design has a high speed jump edge, the transmission line effect on the PCB must be considered. Ixabiso eliphezulu leewotshi zesekethe ezihlanganisiweyo eziqhelekileyo ezisetyenziswa namhlanje zinengxaki nangakumbi. Kukho imigaqo-siseko esisiseko yokusombulula le ngxaki: ukuba iisekthi ze-CMOS okanye ze-TTL zisetyenziselwa uyilo, ukusebenza rhoqo kungaphantsi kwe-10MHz, kwaye ubude beentambo akufuneki bube ngaphezulu kweesentimitha ezi-7. If the operating frequency is 50MHz, the cable length should not be greater than 1.5 inches. Wiring length should be 1 inch if operating frequency reaches or exceeds 75MHz. Ubuninzi bobude beentambo zeetshipsi zeGaAs kufuneka zibe zii-intshi ezingama-0.3. Ukuba oku kugqithisiwe, kukho ingxaki yomgca wokuhambisa.

3. Cwangcisa ngokufanelekileyo ithopholoji yeekhabhi

Another way to solve the transmission line effect is to choose the correct routing path and terminal topology. I-topology ye-cabling ibhekisa kulandelelwano lwekhabhathi kunye nolwakhiwo lwentambo yenethiwekhi. Xa kusetyenziswa izixhobo ezinesantya esiphezulu, uphawu olunemiphetho etshintsha ngokukhawuleza luya kugqwethwa ngamasebe esiqu somqondiso ngaphandle kokuba ubude besebe bugcinwa bufutshane kakhulu. Ngokubanzi, umzila we-PCB wamkela i-topologies ezimbini ezisisiseko, ezizezi yi-Daisy Chain routing kunye ne-Star distribution.

Ngocingo lwe-daisy-chain, i-wiring iqala esiphelweni somqhubi kwaye ifikelele kwisiphelo ngasinye sokufumana ngokulandelelana. If a series resistor is used to change the signal characteristics, the position of the series resistor should be close to the driving end. I-daisy chain cabling yeyona ilungileyo ekulawuleni ukuphazamiseka okuphezulu kwekhabhathi. Nangona kunjalo, olu hlobo lweentambo luneqondo lokuhambisa elisezantsi kwaye akukho lula ukudlula kwi-100%. Kuyilo lokwenyani, sifuna ukwenza ubude besebe kwintambo yeDaisy yocingo lube mfutshane ngokusemandleni, kwaye ubude bexabiso elikhuselekileyo kufanele ukuba: = I-Trt * 0.1.

Umzekelo, isebe liphela ngesantya esiphezulu seesekethe ze-TTL kufuneka libe ngaphantsi kwe-1.5 ye-intshi ubude. Esi sifundo siphezulu sithatha indawo encinci ye-wiring kwaye sinokuyekiswa kukudibana okukodwa. Nangona kunjalo, olu lwakhiwo lweentambo lwenza ukuba isiginali ifumane kumamkeli wesiginali eyahlukileyo ayingqinelani.

The star topology can effectively avoid the problem of clock signal synchronization, but it is very difficult to finish the wiring manually on the PCB with high density. Sebenzisa ikhebula oluzenzekelayo yeyona ndlela yokugqibezela ukufakela iinkwenkwezi. A terminal resistor is required on each branch. The value of the terminal resistance should match the characteristic impedance of the wire. Oku kunokwenziwa ngesandla okanye ngezixhobo ze-CAD ukubala amaxabiso e-impedance kunye namaxabiso okuchasana nesiphelo.

While simple terminal resistors are used in the two examples above, a more complex matching terminal is optional in practice. Inketho yokuqala yitheminali yomdlalo weRC. Ii-terminals ze-RC ezifanayo zinokunciphisa ukusetyenziswa kwamandla, kodwa zinokusetyenziswa kuphela xa ukusebenza komqondiso kuzinzile. Le ndlela ilunge kakhulu kulungelelwaniso lomqondiso wewotshi. Ukungancedi kukuba ukubanakho kwisiphelo sendlela ye-RC kunokuchaphazela ubume kunye nokusasazeka kwesantya somqondiso.

The series resistor matching terminal incurs no additional power consumption, but slows down signal transmission. This approach is used in bus-driven circuits where time delays are not significant. Isiphelo sesixokelelwano sokumelana nesiphelo sinesibonelelo sokunciphisa inani lezixhobo ezisetyenziswa ebhodini kunye noxinano lonxibelelwano.

The final method is to separate the matching terminal, in which the matching element needs to be placed near the receiving end. Uncedo lwayo kukuba ayizukuwudiliza umqondiso, kwaye kunokuba kuhle kakhulu ukunqanda ingxolo. Ngokwesiqhelo isetyenziselwa imiqondiso yokufaka yeTTL (UMTHETHO, HCT, FAST).

In addition, the package type and installation type of the terminal matching resistor must be considered. SMD surface mount resistors generally have lower inductance than through-hole components, so SMD package components are preferred. There are also two installation modes for ordinary straight plug resistors: vertical and horizontal.

Kwimowudi yokuma nkqo, ukumelana kunesikhonkwane esifutshane sokunyusa, esinciphisa ukumelana nobushushu phakathi kokumelana kunye nebhodi yesekethe kwaye yenza ubushushu bokumelana ngokulula bukhutshwe emoyeni. Kodwa ukufakwa okude nkqo kuya kunyusa ukunganyanzeleki kwesixhathisi. Horizontal installation has lower inductance due to lower installation. However, the overheated resistance will drift, and in the worst case, the resistance will become open, resulting in PCB wiring termination matching failure, becoming a potential failure factor.

4. Obunye ubuchwepheshe obusebenzayo

Ukuze kuncitshiswe ukugqithisa kwamandla ombane okwethutyana kunikezelo lwamandla e-IC, ukucoca amandla okugaya kufuneka kongezwe kwi-chip ye-IC. Oku kususa ngokufanelekileyo ifuthe le-burrs kunikezelo lwamandla kwaye kunciphisa ukusasazeka kwemitha kwilogo yamandla kwibhodi eprintiweyo.

Isiphumo sokurholisa i-burr sesona silungileyo xa i-decoupling capacitor iqhagamshelwe ngokuthe ngqo kumlenze wonikezelo lwamandla wesekethe edityanisiweyo kunaleyo yokuhambisa umbane. Kungenxa yoko le nto ezinye izixhobo zine-decoupling capacitors kwiziseko zazo, ngelixa ezinye zifuna umgama phakathi kwe-decoupling capacitor kunye nesixhobo ukuba sincinci ngokwaneleyo.

Nasiphi na isantya esiphezulu kunye nezixhobo zokusebenzisa amandla kufuneka zibekwe ndawonye kangangoko ukunciphisa ugqithiso lwexeshana lokuhambisa umbane.

Ngaphandle kongqimba lwamandla, iilayini zamandla amade zenza iluphu phakathi komqondiso kunye neluphu, esebenza njengomthombo wemitha kunye nesekethe eqhubayo.

I-Cabling eyenza iluphu engadluliyo kwintambo yenethiwekhi efanayo okanye enye ikhabhathi ibizwa ngokuba yi-open loop. Ukuba iluphu idlula kwintambo yenethiwekhi efanayo, ezinye iindlela zenza iluphu evaliweyo. Kuzo zombini ezi meko, iimpembelelo ze-eriyali (i-eriyali yomgca kunye ne-eriyali yomsesane) zinokwenzeka.