Chii chinonzi impedance control uye maitiro ekuita impedance control paPCBs

Mukugadzirwa kwemidziyo yemagetsi yemazuva ano, maPCB anoita basa rakakosha. Kushanda kwemaPCB kunokanganisa zvakananga kugadzikana, kuvimbika uye kushanda zvakanaka kwesystem yese yemagetsi. Pakati pazvo, kutonga kweimpedance chikamu chakakosha chekugadzirwa kwePCB. Sezvo maseketi edhijitari emazuva ano aine nguva pfupi yekutumira masaini uye mwero wewachi wakakwira, maPCB trace haasisiri nyore kubatanidza, asi mitsetse yekutumira zvinoenderana. Kudzora kweimpedance yePCB kunoreva kudzora kumhanya kwekutumira uye kuenderana kweimpedance kwezviratidzo paPCB kuti ive nechokwadi chekuti kutumira masaini kwakanaka uye kwakasimba.

Muzviitiko zvinoshanda, zvinodikanwa kudzora trace impedance kana digital marginal velocity yakakwira kupfuura 1ns kana analog frequency ichipfuura 300MHz. Chimwe chezvinhu zvakakosha zvePCB trace imusiyano wayo (kureva chiyero chevoltage kune current kana wave ichitumirwa pamwe chete nesignal transmission line). Hunhu hwemusiyano wewaya paPCB chiratidzo chakakosha chePCB design. Kunyanya mu high frequency PCB design, zvinodikanwa kufunga kana hunhu hwemusiyano wewaya huchienderana kana hunoenderana nehunhu hunodiwa hwemudziyo kana chiratidzo. Izvi zvinosanganisira pfungwa mbiri: impedance control uye impedance matching. Chinyorwa chino chinotarisa panyaya dzemusiyano control uye stack design.

Kune zviratidzo zvakasiyana-siyana zvinotumirwa mumakondirakita ePCB. Kuti kuvandudza mwero wekutumirwa kwayo, frequency yayo inofanira kuwedzerwa. Kukosha kweimpedance yedunhu pachayo kunosiyana nekuda kwezvinhu zvakaita sekuchekwa, ukobvu hwelayer uye hupamhi hwewaya, nezvimwewo, zvichikonzera kukanganisa kwechiratidzo. Nokudaro, kukosha kweimpedance kwemakondirakita pamaPCB anomhanya zvakanyanya kunofanirwa kudzorwa mukati meimwe nzvimbo, inonzi "impedance control".

Kuvharirwa kwePCB traces kunobva pakupinza kwavo kweinductive ne capacitive, resistance uye coefficient yekufambisa. Zvinhu zvinokanganisa kuvharirwa kwePCB wiring zvinonyanya kusanganisira hupamhi nekukora kwewaya yemhangura, dielectric constant nekukora kwemedium, ukobvu hwesolder pad, nzira yewaya yepasi, uye waya yakatenderedza waya, nezvimwewo. Huwandu hwePCB impedance huri pakati pe25 ne120 ohms.

Mukuita, mitsetse yekutumira yePCB inowanzo kuve newaya trace, imwe kana akawanda mareferensi layers, uye zvinhu zvinodzivirira. Trace nelayer zvinoumba control impedance. PCB dzinowanzo tora ma multi-layer structures, uye impedance control inogonawo kuvakwa nenzira dzakasiyana-siyana. Zvisinei, pasinei nenzira inoshandiswa, impedance value ichatemerwa ne physical structure yayo uye electronic properties yezvinhu zvinodzivirira:

Microstrip itambo yewaya inoreva tambo yekufambisa ine divi rimwe chete rine reference plane. Pamusoro nepamativi zvinoratidzwa mhepo (kana kuti zvinoputirwa) uye zviri pamusoro pe insulation constant Er PCB, ine simba kana ground layer sereference. Sezvakaratidzwa mumufananidzo unotevera:

Cherechedza: Mukugadzirwa kwePCB chaiko, fekitori yePCB inowanzo fukidza inki yegirini pamusoro pePCB. Saka, mukuverenga kweimpedance chaiko, modhi inoratidzwa mumufananidzo unotevera inowanzo shandiswa pamitsetse ye microstrip yepamusoro.

Mutsetse wetambo mutsetse wewaya wakaiswa pakati pemapurani maviri ereferensi, sezvakaratidzwa mumufananidzo unotevera. Zvimisikidzo zve dielectric zve dielectric zvinomiririrwa neH1 neH2 zvinogona kusiyana.

Zviitiko zviviri zviri pamusoro apa zvinongoratidzawo microstrip ne striplines, zvinowanzo shandiswa pakudzidza hardware yeIoT intelligent nedzimwe nzira. Kune mhando dzakawanda dze microstrip ne striplines, dzakadai se coated microstrip, dzine chekuita nechimiro che stacking structure chePCBs.

Equation inoshandiswa kuverenga characteristic impedance inoda masvomhu akaomarara, kazhinji uchishandisa nzira dzekugadzirisa munda, kusanganisira ongororo yezvikamu zvemuganhu. Saka, nekushandisa software yekuverenga impedance yakasarudzika SI9000, chatinongoda kuita chete kudzora maparamita echaracteristic impedance:

Iyo dielectric constant Er ye insulation layer, wiring wiring upamhi W1 na W2 (trapezoidal), wiring thickness T, uye insulation layer thickness H.

W - upamhi hwemutsetse hwakagadzirwa

Kurasikirwa kweA - etch (ona tafura iri pamusoro)

Chikonzero chekusawirirana kwehupamhi pakati pepamusoro nepasi pemutsetse ndechekuti panguva yekugadzira maPCB, ngura inoitika kubva kumusoro kusvika pasi, zvichikonzera chimiro chetrapezoidal chemutsetse une ngura.

Pane hukama hunoenderana pakati peukobvu hwemutsara T nehukobvu hwemhangura hwechikamu ichi, seizvi:

* Nekuda kwehukobvu hudiki hwemasiki e solder pa impedance, inofungidzirwa kuti kukosha kwayo kunogara kuri 0.5mil.

Tinogona kuwana simba rekutonga impedance nekudzora ma parameter aya. Tichitora PCB yepasi yaAnwei semuenzaniso, tichatsanangura matanho ekudzora impedance nekushandiswa kweSI9000:

Chikamu chechipiri ipasi, chikamu chechishanu ipasi, uye chikamu chasara ipasi.

Tsananguro: Dielectric iri pakati pezvikamu zvepakati iFR-4, ine dielectric constant ye4.2; Zvikamu zvepamusoro nepazasi zvikamu zvisina chinhu zvinosangana zvakananga nemhepo, uye dielectric constant yemhepo i1.

Vagadziri vePCB vanogona kushandisa zvizere chimiro chehierarchical chePCBs kuti vawane impedance control. Nekuisa masaini akasiyana munzvimbo dzakasiyana dze layer, interlayer capacitance uye inductance zvinogona kudzorwa zvinobudirira. Kazhinji, interlayer inoshandisa high impedance materials uye outer layer inoshandisa low impedance materials kuderedza simba re reflection uye crosstalk.

Mitsetse yekutumira masaini akasiyana inogona kupa kugona kuri nani kwekudzivirira kukanganiswa uye kuderedza njodzi yekutaura. Mitsetse yekutumira masaini akasiyana iwaya mbiri dzakafanana dzine voltage dzakapesana asi saizi dzakaenzana, izvo zvinogona kupa hunhu huri nani hwechiratidzo uye kugona kwekudzivirira kukanganiswa. Kuvharirwa kwemitsara yekutumira masaini akasiyana kunowanzo dzorwa nekusarudza nzvimbo yemutsara, upamhi uye plane yepasi.

Zvimiro zvejometri zvakaita sehupamhi hwemutsetse wePCB, nzvimbo uye marongerwo zvinogonawo kushandiswa kudzora impedance. Kune mitsetse ye microstrip yakajairika, upamhi hwemutsara wakakora uye nzvimbo yakakura zvinogona kuderedza impedance. Kune mitsetse ye coaxial, dhayamita diki dzemukati uye radii hombe yekunze zvinogona kuwedzera impedance. Kusarudzwa kwegeometry ye wiring kunoda kugadziriswa zvichibva pane zvinodiwa zve impedance uye frequency yesignal.

Kugara kwe dielectric kwezvinhu zvePCB kunokanganisawo impedance. Kusarudza zvinhu zvine hunhu hwakagadzikana hwe dielectric chikamu chekudzora impedance. Mukushandiswa kwema frequency akakwira uye nekukurumidza, zvinhu zvinoshandiswa kazhinji zvinosanganisira FR-4 (girazi fiber reinforced board), PTFE (polytetrafluoroethylene), uye RF (radio frequency) laminates.

Kusati kwagadzirwa PCB, kushandisa maturusi ekufananidzira nekugadzira kunogona kubatsira vagadziri nekukurumidza uye nemazvo kusimbisa nekunatsiridza impedance. Maturusi aya anogona kutevedzera maitiro ecircuit, kurasikirwa kwekutumira masaini uye kutaurirana kwemagetsi kuti aone maparameter ekugadzira PCB akakodzera. Mamwe maturusi ekufananidzira akajairika anosanganisira CST Studio Suite, HyperLynx neADS.

Kudzora impedance yePCB kunoita basa rakakosha mumatanho edhijitari uye analog anomhanyisa. Kuburikidza nekugadzira kwakaringana kwehierarchical, kushandiswa kwemitsetse yekutumira masaini akasiyana, kudzora wiring geometry, kusarudzwa kwezvinhu zvakakodzera zvePCB, uye kushandiswa kwezvishandiso zvekufananidzira nekugadzira, kutonga kwakaringana kwempedance kunogona kuitwa, nokudaro zvichivandudza mashandiro edunhu uye kusimba kwechiratidzo.