In the EMC design of PCB, ukukhathazeka kokuqala ukusethwa kwesendlalelo; Izendlalelo zebhodi zakhiwa ukunikezwa kwamandla, ungqimba lomhlabathi nesendlalelo sesiginali. Ekuklanyeni kwemikhiqizo ye-EMC, ngaphandle kokukhethwa kwezinto nokwakhiwa kwesekethe, ukwakheka okuhle kwe-PCB nakho kuyinto ebaluleke kakhulu.

Ukhiye ekwakhiweni kwe-EMC kwe-PCB ukunciphisa indawo yokubuyela emuva futhi wenze ukugeleza kwendlela yokubuyela emuva kulapho esiklame khona. The layer design is the basis of PCB, how to do a good job of PCB layer design to make the EMC effect of PCB optimal?

Design ideas of PCB layer:

Umnyombo wokuhlelwa nokuklanywa kwe-EMC i-PCB elaminethiwe ukuhlela kahle indlela yokuphindela emuva kwesiginali ukunciphisa indawo yokubuyela emuva kwesiginali kusuka kusendlalelo sesibuko sebhodi, ukuze kuqedwe noma kuncishiswe ukuhamba ngamandla kazibuthe.

1. Board mirroring layer

Isendlalelo sesibuko ungqimba oluphelele lwensimbi yendiza efakwe ithusi (ungqimba lokuphakelwa kwamandla, ungqimba lokumisa phansi) eduze kwesendlalelo sesiginali ngaphakathi kwe-PCB. Imisebenzi esemqoka imi kanje:

(1) Nciphisa umsindo we-backflow: ungqimba lwesibuko lunganikeza indlela ye-impedance ephansi yokugeleza kwesendlalelo sesiginali, ikakhulukazi uma kunokugeleza okukhulu kwamanje ohlelweni lokusabalalisa amandla, indima yesendlalelo sesibuko isobala kakhulu.

(2) Ukuncishiswa kwe-EMI: ubukhona besendlalelo sesibuko kunciphisa indawo yeluphu evaliwe eyakhiwe yisiginali ne-reflux futhi inciphisa i-EMI;

(3) ukunciphisa i-crosstalk: ukusiza ukulawula inkinga ye-crosstalk phakathi kwemigqa yesiginali ngejubane ledijithali, shintsha ukuphakama kolayini wesiginali kusuka kusendlalelo sesibuko, ungalawula i-crosstalk phakathi kolayini besiginali, okuncane ukuphakama, okuncane i-crosstalk;

(4) Ukulawulwa kwe-impedance ukuvimbela ukubonakaliswa kwesiginali.

Ukukhethwa kwesendlalelo sesibuko

(1) Kokubili ukunikezwa kwamandla nendiza yasemhlabeni kungasetshenziswa njengebhanoyi yendiza, futhi kube nomphumela othile wokuvikela ezintanjeni zangaphakathi;

(2) Ngokukhulumayo, indiza yamandla ine-impedance ephezulu yezici, futhi kunomehluko omkhulu ongaba khona ngezinga lesethenjwa, nokuphazamiseka kwemvamisa ephezulu endizeni yamandla kukhulu ngokuqhathaniswa;

(3) Ngokombono wokuvikela, indiza yasemhlabeni ivamise ukubekwa phansi futhi isetshenziswe njengendawo okuyireferensi yezinga lesethenjwa, futhi umphumela wayo wokuvikela ungcono kakhulu kunowo wendiza yamandla;

(4) When selecting the reference plane, the ground plane should be preferred, and the power plane should be selected second.

Magnetic flux cancellation principle:

According to Maxwell’s equations, all electrical and magnetic action between separate charged bodies or currents is transmitted through the intermediate region between them, whether it be a vacuum or solid matter. Ku-PCB, ukugeleza kuhlala kusakazwa kulayini wokudlulisa. Uma indlela ye-rf backflow ifana nendlela yesiginali ehambisanayo, ukugeleza kwendlela yokubuyela emuva kuqonde kolunye uhlangothi kulowo osendleleni yesiginali, khona-ke zibekwa komunye nomunye, futhi umphumela wokukhanselwa kwe-flux utholakala.

Ingqikithi yokukhanselwa kokuhamba kungukulawulwa kwendlela yokubuyela emuva kwesiginali, njengoba kukhonjisiwe kumdwebo olandelayo:

Ungawusebenzisa kanjani umthetho wesandla sokudla ukuchaza umphumela wokukhansela i-magnetic flux lapho ungqimba lwesiginali luseduze nohlaka luchazwa ngale ndlela elandelayo:

(1) Lapho ukugeleza kwamanje ocingweni, kuzokhiqizwa uzibuthe ozungeze ucingo, futhi ukuqondiswa kukazibuthe kunqunywa umthetho wesandla sokudla.

(2) lapho kunezimbili eziseduze komunye nomunye futhi ezihambisana nentambo, njengoba kukhonjisiwe esithombeni esingezansi, omunye wabaqhubi bokukhipha ugesi, omunye umqhubi kagesi ogeleza, uma amandla kagesi egeleza i-wire ingeyamanje nesiginali yayo yokubuyisa yamanje, khona-ke izinkomba ezimbili eziphikisanayo zamanje ziyalingana, ngakho-ke amandla kazibuthe ayalingana, kepha isiqondiso siphambene,Ngakho-ke bayakhansela.

Six layer board design example

1. For six-layer plates, scheme 3 is preferred;

Ukuhlaziywa:

(1) Njengoba ungqimba lwesiginali luseduze nendiza yesithenjwa, futhi i-S1, S2 ne-S3 ziseduze nendiza yomhlaba, umphumela omuhle kakhulu wokukhansela i-magnetic flux uyatholakala. Ngakho-ke, i-S2 ungqimba lomzila olukhethwayo, olulandelwa i-S3 ne-S1.

(2) Indiza yamandla iseduze kwendiza ye-GND, ibanga eliphakathi kwezindiza lincane kakhulu, futhi inomphumela omuhle kakhulu wokukhansela i-magnetic flux kanye ne-impedance yendiza yamandla aphansi.

(3) Amandla kagesi amakhulu kanye nendwangu yawo ehambelana nendawo atholakala kusendlalelo 4 no-5. Lapho kusethwe ukushuba kwesendlalelo, isikhala phakathi kwe-S2-P kufanele sikhuliswe futhi isikhala phakathi kwe-P-G2 sinciphiswe (isikhala phakathi kongqimba I-G1-S2 kufanele incishiswe ngokufanayo), ukuze kuncishiswe ukuvinjelwa kwendiza yamandla nomthelela wamandla ku-S2.

2. When the cost is high, scheme 1 can be adopted;

Ukuhlaziywa:

(1) Because the signal layer is adjacent to the reflow reference plane and S1 and S2 are adjacent to the ground plane, this structure has the best magnetic flux cancellation effect;

(2) Due to the poor magnetic flux cancellation effect and high power plane impedance from the power plane to the GND plane through S3 and S2;

(3) Preferred wiring layer S1 and S2, followed by S3 and S4.

3. For six-layer plates, option 4

Ukuhlaziywa:

Isikimu 4 silunge ngaphezu kweSikimu 3 sendawo, isibalo esincane sezimfuneko zesiginali, esinganikeza ungqimba lwezintambo oluhle kakhulu i-S2.

4. Worst EMC effect, Scheme,Ukuhlaziywa:

In this structure, S1 and S2 are adjacent, S3 and S4 are adjacent, and S3 and S4 are not adjacent to the ground plane, so the magnetic flux cancellation effect is poor.

Cukukhishwa

Izimiso ezithile ze-PCB design design:

(1) Kukhona indiza yomhlaba ephelele (isihlangu) ngaphansi kwendawo yengxenye nobuso bensimbi;

(2) Zama ukugwema okuqondana ngqo nezendlalelo ezimbili zamasignali;

(3) Zonke izingqimba zesiginali ziseduze nendiza yasemhlabeni ngangokunokwenzeka;

(4) Isendlalelo sentambo semvamisa ephezulu, isivinini esikhulu, iwashi namanye amasiginali asemqoka kufanele abe nendiza yomhlaba eseduze.