In PCB Ukubamba iintambo, kuhlala kwenzeka ukuba umgca osondeleyo kufuneka usetyenziselwe ukugqitha kwindawo apho kukho isithuba sokubophelela, kwaye umgca ubuyiselwe kububanzi bayo bokuqala. Utshintsho kububanzi bomgca luya kubangela utshintsho kwimpedance, eya kuthi ikhokelele ekuboniseni kwaye ichaphazele uphawu. Ke singayihoya nini le mpembelelo, kwaye kufuneka siqwalasele nini umphumo wayo?

Izinto ezintathu zinxulumene nesi siphumo: ubukhulu benguquko yempedance, ixesha lokunyuka komqondiso, kunye nokulibaziseka komqondiso kumgca omxinwa.

Okokuqala, ubungakanani botshintsho lwe-impedance buxoxwa. Uyilo lweesekethe ezininzi ludinga ukuba ingxolo ebonisiweyo ibe ngaphantsi kwe-5% ye-voltage swing (ehambelana nohlahlo-lwabiwo mali lwengxolo kumqondiso), ngokomgaqo wefomyula eyoneleyo:

Ixabiso lokutshintsha kwe-impedance linokubalwa njenge-/ Z / Z1 ≤ 10%. Njengoko uyazi, isalathi esiqhelekileyo sokungxamiseki kwibhodi ngu +/- 10%, kwaye sisona sizathu sengcambu.

Ukuba utshintsho lwe-impedance lwenzeka kube kanye kuphela, njengaxa ububanzi bomgca butshintsha ukusuka kwi-8mil ukuya kwi-6mil kwaye buhlala bu-6mil, utshintsho lwe-impedance kufuneka lube ngaphantsi kwe-10% ukuze kufikelelwe kwimfuno yohlahlo-lwabiwo mali yengxolo yokuba umqondiso ubonakalise ingxolo kutshintsho olukhawulezileyo ungadluli kwi-5% yamandla ombane ojingayo. Ngamanye amaxesha kunzima ukwenza. Thatha imeko yemigca ye-microstrip kwiipleyiti ze-FR4 njengomzekelo. Masibale. Ukuba ububanzi bomgca buyi-8mil, ubukhulu phakathi komgca kunye nenqwelomoya yenqwelomoya yi-4mil kunye ne-impedance yempawu eyi-46.5 ohms. Xa ububanzi bomgca butshintsha bube yi-6mil, impedance yesimo iba yi-54.2 ohm, kwaye i-impedance change rate ifikelela kuma-20%. Ukuphakama kwesiginali ebonakalisiweyo kufuneka kudlule kumgangatho. Malunga nefuthe elingakanani kwisignali, kodwa kunye nexesha lokunyuka komqondiso kunye nokulibaziseka kwexesha ukusuka kumqhubi ukuya kumqondiso wenqaku elibonisayo. Kodwa ubuncinci inokuba yingxaki. Ngethamsanqa, unokuyicombulula ingxaki ngeeterminal ezifanayo.

Ukuba utshintsho lwe-impedance lwenzeka kabini, umzekelo, ububanzi bomgca butshintsha ukusuka kwi-8mil ukuya kwi-6mil, kwaye emva koko utshintshe ubuyele kwi-8mil emva kokukhupha i-2cm. Ke kwi-2cm ubude be-6mil ububanzi kumacala omabini okubonisa, enye ye-impedance iba nkulu, ibonakalise okuhle, kwaye ke i-impedance iba ncinane, ibonakalise ukungalunganga. Ukuba ixesha eliphakathi kokuboniswa lifutshane ngokwaneleyo, oku kubonakalisa kunokucima omnye komnye, kunciphise ukusebenza. Ukuthatha ukuba isiginali yokudlulisela yi-1V, i-0.2V ibonakalisiwe kwisibonakaliso sokuqala esihle, i-1.2V idluliselwe phambili, kwaye -0.2 * 1.2 = 0.24V ibonakalisiwe emva kwisibonakaliso sesibini. Ukuthatha ukuba ubude bomgca we-6mil bufutshane kakhulu kwaye ukubonakaliswa kokubini kwenzeka phantse ngaxeshanye, itotali ebonisiweyo iyonke yi-0.04V kuphela, ingaphantsi kwemfuneko yohlahlo-lwabiwo mali lwe-5%. Ke ngoko, nokuba kwaye kungakanani kwaye oku kubonakalisa kuchaphazela njani umqondiso kuxhomekeke kulibaziseko lwexesha kutshintsho lwempedance kunye nexesha lokunyuka komqondiso. Izifundo kunye novavanyo lubonisa ukuba okoko nje ukulibaziseka kutshintsho lwe-impedance kungaphantsi kwe-20% yexesha lokunyuka komqondiso, uphawu olubonakalisiweyo aluyi kubangela ngxaki. Ukuba ixesha lokunyuka komqondiso li-1ns, ukulibaziseka kotshintsho lwe-impedance kungaphantsi kwe-0.2ns ehambelana nee-intshi ze-1.2, kwaye ukubonakaliswa akuyongxaki. Ngamanye amagama, kule meko, ubude be-6mil ebanzi yocingo engaphantsi kwe-3cm akufuneki ibe yingxaki.

Xa ububanzi bokubumba kweengcingo ze-PCB, kufanele ukuba buhlalutywe ngononophelo kwimeko eyiyo ukubona ukuba akukho mpembelelo. Zintathu iiparameter ekufuneka uzixhalabisile malunga nokuba ingakanani i-impedance etshintsha, ixesha elingakanani lokunyuka komqondiso, kunye nokuba lide kangakanani ixesha elinjengentamo elinjengobubanzi bolayini obuguqukayo. Yenza uqikelelo olunzima ngokusekwe kule ndlela ingentla kwaye ushiye umda othile ngokufanelekileyo. Ukuba kunokwenzeka, zama ukunciphisa ubude bentamo.

Kufuneka ibonakaliswe ukuba kulwenziwo lwePCB uqobo, iiparameter azinakuba zichanekile njengezo zikwithiyori. Ithiyori inokunika isikhokelo kuyilo lwethu, kodwa ayinakukopishwa okanye iqinisekiswe. Emva kwayo yonke loo nto yisayensi esebenzayo. Ixabiso eliqikelelweyo kufuneka lihlaziyiwe ngokweyona meko, emva koko lisetyenziswe kuyilo. Ukuba uziva ungenamava, zigcine kwaye uhlengahlengise kwiindleko zokwenza.