Ahoana ny fomba hisorohana ny vokan’ny tsipika fampitana ao haingam-pandeha PCB famolavolana

1. Fomba entina manakana ny fanelingelenana elektromagnetika

Ny vahaolana tsara amin’ny olan’ny tsy fivadihana famantarana dia hanatsara ny fifandraisan’ny electromagnetic (EMC) amin’ny tabilao PCB. Ny iray amin’ireo zava-dehibe indrindra dia ny fiantohana ny fikajiana ny PCB board. Ny sosona famantarana misy sosona amin’ny tany dia fomba tena mahomby amin’ny famolavolana sarotra. Ho fanampin’izany, ny fanamafisana ny hakitroky ny signal an’ny sosona ivelany indrindra amin’ny fantsom-pifandraisana dia fomba tsara ihany koa hampihenana ny taratra elektromagnetika. Ity fomba ity dia azo tanterahina amin’ny alàlan’ny fampiasana ny haitao PCB “build-up” teknolojia “build-up” PCB. Ny sosona amin’ny velarana dia tratra amin’ny alàlan’ny fampifangaroana ireo sosona insulate manify sy micropores ampiasaina mba hidirana amin’ireo sosona ireo amin’ny PCB amin’ny ankapobeny. Ny fanoherana sy ny capacitance dia azo halevina ao ambanin’ny tany, ary ny hakitroky ny tsipika isaky ny faritra iray dia saika avo roa heny, ka mampihena ny fatran’ny PCB. Ny fihenan’ny faritra PCB dia misy fiatraikany lehibe amin’ny topolojia ny fitaterana, izay midika fa mihena ny tadim-poitra ankehitriny, mihena ny halavan’ny làlan’ny sampana, ary ny taratra elektromagnetika dia mitovy amin’ny faritry ny loop ankehitriny; 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. Ny tahan’ny famantaranandro faratampon’ny finday izay ampiasaina matetika ankehitriny dia mbola olana kokoa. Misy fitsipika fototra hamahana an’ity olana ity: raha CMOS na TTL boribory no ampiasaina amin’ny famolavolana, ny faharetan’ny asa dia ambany noho ny 10MHz, ary ny halavan’ny tariby dia tsy tokony ho lehibe mihoatra ny 7 santimetatra. 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. Ny halavan’ny tariby ambony indrindra ho an’ny chipAgasy dia tokony ho 0.3 santimetatra. Raha mihoatra izany dia misy olana amin’ny zotra fampitana.

3. Alamino tsara ny topolojia misy ny cabling

Fomba iray hafa hamahana ny vokan’ny tsipika fandefasana ny fisafidianana ny làlam-pandeha marina sy ny topolojia terminal. Ny topology momba ny cabling dia manondro ny filaharana sy ny rafitry ny tariby tambajotra. Rehefa ampiasaina ny fitaovana lojika haingam-pandeha, ny famantarana miaraka amin’ny sisiny miova haingana dia hodiovin’ny sampan’ny vatan’ny signal raha tsy hoe fohy ny halavan’ny sampana. Amin’ny ankapobeny, ny fitetezana PCB dia mandray topolojia roa fototra, dia ny fizarana Daisy Chain ary ny fizarana Star.

Ho an’ny tariby daisy-rojo dia manomboka amin’ny tariby mpamily ny tariby ary tonga isaky ny fiafarany. Raha resistor andian-dahatsoratra ampiasaina hanovana ny toetra mampiavaka ny famantarana, ny toerana misy ny resistor andian-dahatsoratra dia tokony ho akaikin’ny fiafaran’ny fiara. Ny kofehy Daisy rojo no tsara indrindra amin’ny fifehezana ny fitsabahan’ny harmonika avo lenta amin’ny cabling. Na izany aza, ity karazana tariby ity dia manana ny tahan’ny fandefasana ambany indrindra ary tsy mora ny mandalo 100%. Amin’ny famolavolana tena izy dia tianay ny hametahana ny halavan’ny sampana amin’ny tariby Daisy rojovy fohy araka izay azo atao, ary ny sandan’ny halavany azo antoka dia tokony: Stub Delay < = Trt * 0.1.

Ohatra, ny sampana dia mifarana amin’ny haingam-pandeha TTL haingam-pandeha dia tokony ho latsaky ny 1.5 santimetatra ny halavany. Ity topolojia ity dia mandray toerana kely kokoa amin’ny tariby ary azo esorina amin’ny alàlan’ny resistor tokana. Na izany aza, ity firafitry ny tariby ity dia mahatonga ny fambara fandraisana amin’ny mpandray fambara tsy mitovy.

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. Ny fampiasana cabler mandeha ho azy no fomba tsara indrindra hamitana ny cabling kintana. A terminal resistor is required on each branch. The value of the terminal resistance should match the characteristic impedance of the wire. Izy io dia azo atao amin’ny tanana na amin’ny alàlan’ny fitaovana CAD mba hikajiana ny soatoavin’ny impedance sy ny sandan’ny fanoherana mifanaraka amin’ny terminal.

While simple terminal resistors are used in the two examples above, a more complex matching terminal is optional in practice. Ny safidy voalohany dia ny terminal match RC. Ny terminal mifampitohy RC dia afaka mampihena ny fanjifana herinaratra, saingy azo ampiasaina ihany rehefa miorina tsara ny fiasan’ny signal. Ity fomba ity dia mety indrindra amin’ny fanodinana fampitoviana tsipika famantaranandro. Ny fatiantoka dia ny capacitance ao amin’ny terminal mifanandrify RC mety hisy fiatraikany amin’ny endrika sy ny hafainganam-pandehan’ny fambara.

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. Ny terminal fanoherana mifanohitra amin’ny andian-dahatsoratra dia manana tombony ihany koa amin’ny fampihenana ny isan’ny fitaovana ampiasaina amin’ny solaitrabe sy ny hakitroky ny fifandraisana.

The final method is to separate the matching terminal, in which the matching element needs to be placed near the receiving end. Ny tombony dia ny tsy hanongotany ny signal, ary mety ho tena tsara hisorohana ny tabataba. Ampiasaina matetika ho an’ny signal input TTL (ACT, 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.

Amin’ny maodely fitobiana mitsangana, ny fanoherana dia manana pin matevina fohy, izay mampihena ny fanoherana hafanana eo anelanelan’ny fanoherana sy ny tabilao mihodina ary mahatonga ny hafanan’ny fanoherana mora kokoa hamoaka amin’ny rivotra. Fa ny fametrahana mitsangana lava kokoa dia hampitombo ny fidiran’ny resistor. Ny fametrahana marindrano dia misy inductance ambany noho ny fametrahana ambany kokoa. 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. Teknolojia hafa azo ampiharina

Mba hampihenana ny fihoaram-pefy mandritra ny fotoana fohy amin’ny famatsiana herinaratra IC, tokony ampiana capacitor decoupling amin’ny puce IC. Io dia manala amin’ny fomba mahomby ny fiantraikan’ny burrs amin’ny famatsian-jiro ary mampihena ny taratra avy amin’ny tadin’ny herinaratra eo amin’ny solaitrabe vita pirinty.

Ny effet burr smoothing dia tsara indrindra raha ny capacitor decoupling dia ampifandraisina mivantana amin’ilay tongotra manome tsiranoka amin’ny circuit miharo fa tsy amin’ny elatra famatsiana herinaratra. Izany no mahatonga ny fitaovana sasany hanana decoupling capacitors ao amin’ny faladiany, fa ny sasany kosa mitaky ny elanelana misy eo amin’ny capacitor decoupling sy ny fitaovana ho ampy kely.

Ny fitaovana haingam-pandeha haingam-pandeha sy haingam-pandeha dia tokony hapetraka arak’izay tratra mba hampihenana ny fanodinkodinan’ny herinaratra mandritra ny fotoana fohy.

Raha tsy misy sosona herinaratra, ny tadin’ny herinaratra lava dia mamorona tadivavarana eo anelanelan’ny signal sy ny loop, izay loharanom-taratra sy tariby inductive.

Ny cabling mamorona loop izay tsy mandalo tariby tambajotra na cabling hafa dia antsoina hoe loop open. Raha toa ka mamakivaky tariby tambajotra iray ihany ny tadiavina, dia misy loop hafa mihidy. Amin’ireo tranga roa ireo dia mety hitranga ny vokatra antena (antena tsipika sy antena peratra).