In PCB mai sauri ƙira, aikace-aikacen siginar bambance-bambance (Siginar DIFferential) yana ƙara ƙaruwa, kuma mafi mahimmancin sigina a cikin kewayawa sau da yawa ana tsara shi tare da tsari mai ban sha’awa. Me yasa haka? Idan aka kwatanta da na yau da kullun na sigina mai ƙarewa guda ɗaya, sigina daban-daban suna da fa’idodin ƙarfin hana tsangwama, tasiri mai tasiri na EMI, da daidaitaccen matsayi na lokaci.

Bukatun wayoyi na PCB na sigina daban

A kan allon kewayawa, alamun bambance-bambancen dole ne su kasance layi biyu masu tsayi daidai, daidai da faɗi, kusanci, kuma a kan matakin ɗaya.

1. Tsawon daidai: Tsawon daidaici yana nufin cewa tsawon layin biyu ya kamata ya kasance gwargwadon iko, don tabbatar da cewa siginar banbance-banbance guda biyu suna kiyaye kishiyar polarities koyaushe. Rage abubuwan gama gari gama gari.

2. Daidaitaccen faɗi da nisa: Daidaitaccen faɗi yana nufin cewa faɗin alamun sigina biyu yana buƙatar kiyaye shi daidai, kuma daidaitaccen tazarar yana nufin a kiyaye tazarar da ke tsakanin wayoyi biyu kuma a daidaita.

3. Canjin ƙaƙƙarfan rashin ƙarfi: Lokacin zayyana PCB tare da sigina daban-daban, ɗayan mahimman abubuwan shine gano maƙasudin maƙasudin aikace-aikacen, sannan shirya nau’ikan nau’ikan daban-daban daidai. Bugu da ƙari, ci gaba da canza impedance a matsayin ƙarami kamar yadda zai yiwu. Matsakaicin layin banbanta ya dogara da abubuwa kamar nisa alama, haɗaɗɗun alama, kaurin jan ƙarfe, da kayan PCB da tari. Lokacin da kuke ƙoƙarin guje wa duk wani abu da ke canza impedance na nau’i-nau’i daban-daban, la’akari da kowannensu.

Rashin fahimtar juna na gama gari a ƙirar siginar bambancin PCB

Rashin fahimta 1: An yi imanin cewa siginar banbanta ba ya buƙatar jirgin sama a matsayin hanyar dawowa, ko kuma cewa bambance-bambancen suna ba da hanyar dawowa ga juna.

Dalilin wannan rashin fahimta shi ne, an ruɗe su da abubuwan da ba a sani ba, ko kuma tsarin watsa sigina mai sauri bai isa ba. Daban-daban da’irori ba su da hankali ga irin wannan bounces na ƙasa da sauran siginonin amo waɗanda za su iya kasancewa a kan wutar lantarki da jiragen ƙasa. Sake dawo da wani ɓangare na jirgin ƙasa baya nufin cewa bambancin kewayawa baya amfani da jirgin sama azaman hanyar dawowar sigina. A haƙiƙa, a cikin binciken dawo da siginar, tsarin na’ura mai ba da hanya tsakanin hanyoyin sadarwa da na’urorin sadarwa na yau da kullun iri ɗaya ne, wato, sigina masu tsayi koyaushe suna Reflow tare da madauki tare da ƙaramin inductance. Babban bambanci shi ne, ban da haɗin kai zuwa ƙasa, layin bambancin kuma yana da haɗin gwiwar juna. Wanne nau’in haɗin gwiwa ne mai ƙarfi, kuma wanne ne ya zama babbar hanyar dawowa.

A cikin ƙirar da’irar PCB, haɗin kai tsakanin alamun bambance-bambancen gabaɗaya kaɗan ne, galibi kawai ana lissafin 10-20% na digiri na haɗin gwiwa, kuma ƙari shine haɗakarwa zuwa ƙasa, don haka babban hanyar dawowar alamar bambancin har yanzu tana nan akan ƙasa. jirgin sama . Lokacin da aka samu dakatarwa a cikin jirgin sama, haɗin kai tsakanin nau’o’in bambance-bambancen da ke cikin yankin ba tare da jirgin sama ba zai ba da babbar hanyar dawowa, ko da yake katsewar jirgin sama ba shi da tasiri a kan bambance-bambance a kan talakawa guda ɗaya. burbushi Yana da mahimmanci, amma har yanzu zai rage ingancin siginar banbanta da ƙara EMI, wanda yakamata a kauce masa gwargwadon yiwuwa.

Bugu da kari, wasu masu zanen kaya sun yi imanin cewa za a iya cire jirgin da ke karkashin sawun bambance-bambancen don murkushe wani bangare na siginar yanayin gama gari a cikin watsa banbanci. Duk da haka, wannan hanya ba a so a ka’idar. Yadda za a sarrafa impedance? Rashin samar da madauki na ƙasa don siginar yanayin gama gari ba makawa zai haifar da radiation na EMI. Wannan hanya tana da cutarwa fiye da kyau.

Rashin fahimta 2: An yi imani cewa kiyaye tazarar daidai ya fi mahimmanci fiye da daidaita tsayin layi.

A cikin ainihin shimfidar PCB, sau da yawa ba zai yiwu a cika buƙatun ƙirar ƙira a lokaci guda ba. Saboda kasancewar abubuwa kamar rarraba fil, vias, da sararin wayoyi, dole ne a cimma manufar daidaita tsayin layin ta hanyar iskar da ta dace, amma sakamakon dole ne ya zama cewa wasu wuraren banbancen biyu ba za su iya zama daidai ba. Mafi mahimmancin doka a cikin ƙira na alamun bambancin PCB shine tsayin layin da ya dace. Wasu dokoki za a iya sarrafa su cikin sassauƙa bisa ga buƙatun ƙira da ainihin aikace-aikace.

Rashin fahimta 3: Yi tunanin cewa bambancin wayoyi dole ne ya kasance kusa sosai.

Tsayawa bambance-bambancen burbushi kusa ba komai bane illa haɓaka haɗin gwiwar su, wanda ba wai kawai inganta rigakafi ga hayaniya ba ne, amma kuma yin cikakken amfani da akasin polarity na filin maganadisu don kashe kutse na lantarki zuwa duniyar waje. Kodayake wannan hanyar tana da fa’ida sosai a mafi yawan lokuta, ba cikakke ba ce. Idan za mu iya tabbatar da cewa an kare su gaba ɗaya daga tsoma baki na waje, to ba ma buƙatar yin amfani da haɗin gwiwa mai ƙarfi don cimma nasarar tsangwama. Da kuma manufar danne EMI.

Ta yaya za mu iya tabbatar da keɓantawa mai kyau da garkuwar alamomi daban? Ƙara tazara tare da sauran alamun sigina yana ɗaya daga cikin manyan hanyoyin. Ƙarfin filin lantarki yana raguwa tare da murabba’in nisa. Gabaɗaya, lokacin da tazarar layin ya wuce faɗin layin sau 4, tsangwama a tsakanin su yana da rauni sosai. Ana iya yin watsi da su.