Sida looga fogaado saamaynta khadka gudbinta gudaha PCB-xawaaraha sare design

1. Hababka lagu xakameeyo faragelinta elektromagnetka

Xalka wanaagsan ee dhibaatada sharafta signalada ayaa wanaajin doonta iswaafajinta elektromagnetiga (EMC) ee guddiga PCB. Mid ka mid ah kuwa ugu muhiimsan ayaa ah in la hubiyo in guddiga PCB uu leeyahay saldhig wanaagsan. Lakabka signal oo leh lakab dhulka ah ayaa ah hab aad wax ku ool u ah naqshadaynta adag. Intaa waxaa dheer, yaraynta cufnaanta calaamadda ee lakabka ugu sarreeya ee guddiga wareegga sidoo kale waa hab wanaagsan oo lagu yareeyo shucaaca elektromagnetigga. Habkan waxaa lagu gaari karaa iyadoo la adeegsanayo tiknoolajiyadda “aagga dushiisa” “dhisidda” naqshadda PCB. Lakabka dhulka dushiisa waxaa lagu gaaraa iyada oo lagu daro isku-darka lakabyo dahaarka khafiifka ah iyo makarafoorro loo isticmaalo in lagu dhex maro lakabyada PCB-ga guud-socodka. Iska caabbinta iyo kartida ayaa lagu duugi karaa dusha sare, iyo cufnaanta toosan ee aagga unug kasta ayaa ku dhowaad labanlaabantay, sidaasna lagu yareynayaa mugga PCB. Yaraynta aagga PCB waxay saamayn weyn ku leedahay topology of routing, taas oo macnaheedu yahay in loop -ka hadda jira la yareeyo, dhererka dariiqa laanta ayaa la dhimay, iyo shucaaca elektromagnetic -ku wuxuu u dhigmaa qiyaasta aagga loop -ka hadda; 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. Heerka sare ee saacadaha isku -dhafan ee isku -dhafan ee isku -dhafan oo caadi ahaan maanta la isticmaalo ayaa xitaa dhib badan. Waxaa jira mabaadi’da aasaasiga ah ee lagu xallinayo dhibaatadan: haddii wareegyada CMOS ama TTL loo adeegsado naqshadeynta, inta jeer ee hawlgalka ay ka yar tahay 10MHz, dhererka xariguna uusan ka weynaan 7 inji. 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. Dhererka ugu sarreeya ee fiilooyinka GaAs chips waa inuu ahaadaa 0.3 inji. Haddii tan la dhaafo, waxaa jira dhibaato khadka gudbinta.

3. Si habboon u qorshee dhul -beereedka cabbitaanka

Hab kale oo lagu xaliyo saamaynta khadka gudbinta ayaa ah in la doorto dariiqa saxda ah ee marin -habaabinta iyo topology -ga ugu dambeeya. Dhul -gariirka cabling wuxuu loola jeedaa isku xigxiga xarigga iyo qaab -dhismeedka fiilada shabakadda. Marka la adeegsado aaladaha macquulka ah ee xawaaraha sare leh, signalka leh geesaha si dhaqso leh isu beddelaya waxaa qalloocin doona laamaha jirridda signal haddii dhererka laanta aan aad loo gaabin. Guud ahaan, waddada PCB -du waxay qaadataa laba meelood oo aasaasi ah, kuwaas oo kala ah Daisy Chain routing iyo qaybinta Xiddiga.

Si loogu xiro silsiladda daisy-silsiladda, xariggu wuxuu ka bilaabmaa darawalka darafkiisa wuxuuna gaaraa dhammaadka helitaankiisa markiisa. Haddii resistor taxane ah loo isticmaalo in lagu beddelo astaamaha signalada, booska resistor -ka taxanaha ahi waa inuu ku dhowaadaa dhammaadka wadista. Xadhigga silsiladda Daisy ayaa ugu fiican xakamaynta faragelinta iswaafaqsan ee xadhigga. Si kastaba ha ahaatee, fiilooyinka noocan ahi waxay leeyihiin heerka gudbinta ugu hooseeya mana fududa in la dhaafo 100%. Naqshadda dhabta ah, waxaan rabnaa inaan dhererka laanta ka dhigno xarigga silsiladda Daisy sida ugu gaaban ee suurtogalka ah, iyo qiimaha dhererka nabdoon waa inuu ahaado: Dib -u -dhac Stub < = Trt * 0.1.

Tusaale ahaan, laantu waxay ku dhammaataa wareegyada TTL ee xawaaraha sare leh waa inay ka yaraato 1.5 inji. Topology -gaani wuxuu qaadanayaa meel fiilo oo yar waxaana lagu joojin karaa hal resistor oo u dhigma. Si kastaba ha ahaatee, qaab -dhismeedka xarigani wuxuu ka dhigayaa in signal -ka qaataha qaataha signal -ka ee kala duwan uusan ahayn mid isku mid ah.

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. Isticmaalka cabler otomaatig ah ayaa ah habka ugu fiican ee lagu dhammaystiro xarigga xiddigta. A terminal resistor is required on each branch. The value of the terminal resistance should match the characteristic impedance of the wire. Tan waxaa lagu samayn karaa gacanta ama iyada oo loo marayo aaladaha CAD si loo xisaabiyo qiyamka impedance dabeecadda iyo qiyamka iska -caabbinta ee u dhigma.

While simple terminal resistors are used in the two examples above, a more complex matching terminal is optional in practice. Ikhtiyaarka koowaad waa terminal -ka ciyaarta RC. Tilmaamaha iswaafajinta RC waxay yarayn karaan isticmaalka korontada, laakiin waxaa la isticmaali karaa oo keliya marka hawlgalka signaalku uu yara deggan yahay. Habkani wuxuu aad ugu habboon yahay ka shaqaynta isbarbar dhigga signaalka saacadda. Faa’iido darradu waxay tahay in awoodda ku jirta gantaalka RC ee u dhiganta ay saamayn ku yeelan karto qaabka iyo xawaaraha faafinta calaamadda.

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. Terminalka isbarbar dhigga taxanaha ayaa sidoo kale leh faa iido yaraynta tirada aaladaha loo isticmaalo sabuuradda iyo cufnaanta isku xirnaanta.

The final method is to separate the matching terminal, in which the matching element needs to be placed near the receiving end. Faa’iidadeedu waxay tahay in aysan hoos u riixin signalada, oo aad bay u fiicnaan kartaa in laga fogaado buuqa. Caadi ahaan waxaa loo adeegsadaa calaamadaha 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.

Qaabka kor u qaadista tooska ah, iska -caabbintu waxay leedahay biin dhejis gaaban, taas oo yareynaysa iska -caabbinta kuleylka ee u dhexeeya iska -caabbinta iyo guddiga wareegga oo ka dhigaysa kuleylka iska -caabbinta mid si sahlan hawada loogu sii daayo. Laakiin rakibidda tooska ah ee dheeraadka ah waxay kordhin doontaa inductance of resistor. Rakibaadda Horizontal waxay leedahay hoos -u -dhac hooseeya sababtoo ah rakibidda hoose. 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. Farsamooyin kale oo lagu dabaqi karo

Si loo yareeyo korantada ku -meelgaarka ah ee korantada korantada IC, waa in lagu daraa qalabka korantada ee IC. Tani waxay si wax ku ool ah uga saareysaa saamaynta burrs -ku ku leeyihiin korontada waxayna yareyneysaa shucaaca ka soo baxa wareegga korontada ee sabuuradda daabacan.

Saamaynta jilcinta burr ayaa ugu fiican marka koronto -hayaha kala -goynta uu si toos ah ugu xiran yahay lugta korontada ee wareegga isku -dhafan halkii uu ka ahaan lahaa lakabka korontada. Tani waa sababta aaladdaha qaarkood ay ku leeyihiin koronto -dejiyayaasha godadkooda godadka, halka kuwa kalena ay u baahan yihiin masaafada u dhexeysa koronto -gooyaha iyo aaladda inay yaraato.

Xawaare kasta oo sarreeya iyo aaladaha isticmaalka korontada sare waa in la wada dhigaa intii suurtogal ah si loo yareeyo kororka ku -meelgaarka ah ee korantada korontada.

Lakabka korontada la’aanteed, khadadka korontada dhaadheer ayaa sameeya loop u dhexeeya signalada iyo loop -ka, oo u adeega ilaha shucaaca iyo wareegga inductive.

Kaxaynta samaynta loop oo aan soo marin isla fiilada shabakadda ama xarig kale ayaa loo yaqaan loop furan. Haddii loopku ka gudbo isla fiilada shabakadda, waddooyin kale ayaa sameeya loop xiran. Labada xaaladoodba, saamaynta anteenada (anteenada xariiqa iyo anteenada giraantu) way dhici kartaa.