Kunyezimira kwa siginecha kungayambitse kulira. Kulira kwachizindikiro kukuwonetsedwa mu Chithunzi 1.

Ndiye kodi kulira kwa siginecha kumachitika bwanji?

Monga tanenera kale, ngati kusintha kwa impedance kumamveka panthawi yotumiza chizindikiro, kuwunikira kwa chizindikiro kudzachitika. Chizindikiro ichi chikhoza kukhala chizindikiro chotumizidwa ndi dalaivala, kapena chikhoza kukhala chizindikiro chowonekera kuchokera kumapeto. Malinga ndi chiwonetsero cha coefficient formula, chizindikiro chikawona kuti cholepheretsacho chikhala chocheperako, mawonekedwe oyipa amachitika, ndipo mphamvu yowoneka bwino imapangitsa kuti siginecha idutse. Chizindikirocho chimawonetsedwa kangapo pakati pa dalaivala ndi katundu wakutali, ndipo zotsatira zake ndi kulira kwa chizindikiro. Kutulutsa kwa tchipisi zambiri ndikotsika kwambiri. Ngati linanena bungwe impedance ndi zochepa kuposa khalidwe impedance wa PCB kutsatira, kulira kwa siginecha kudzachitika ngati palibe kutha kwa gwero.

Njira yoyimba siginecha imatha kufotokozedwa momveka bwino ndi chithunzi cha bounce. Kungoganiza kuti kutsekeka kwa kutha kwa ma drive ndi 10 ohms, ndipo mawonekedwe a PCB trace ndi 50 ohms (atha kusinthidwa ndikusintha m’lifupi mwa trace ya PCB, makulidwe a dielectric pakati pa PCB trace ndi mbiri yamkati. ndege), kuti zitheke kusanthula, tiyerekeze kuti malekezero akutali ndi otseguka , Ndiko kuti, kutsekeka kwakutali kuli kopanda malire. Kumapeto kwa galimoto kumatumiza chizindikiro cha 3.3V. Tiyeni titsatire chizindikiro ndikudutsa mumsewu wotumizira kamodzi kuti tiwone zomwe zidachitika. Kuti zikhale zosavuta kusanthula, chikoka cha parasitic capacitance ndi parasitic inductance ya mzere wopatsirana sichimaganiziridwa, ndipo katundu wotsutsa yekha amaganiziridwa. Chithunzi 2 ndi chithunzi chowonetsera.

Chiwonetsero choyamba: chizindikirocho chimatumizidwa kuchokera ku chip, pambuyo pa 10 ohm kutulutsa mphamvu ndi 50 ohm PCB khalidwe lachidziwitso, chizindikiro chomwe chinawonjezeredwa ku PCB trace ndi mphamvu yamagetsi pa A 3.3 * 50 / (10 + 50) = 2.75 V. Kutumiza kumalo akutali B, chifukwa mfundo B ndi yotseguka, kutsekereza kulibe malire, ndipo chigawo chowonetsera ndi 1, ndiko kuti, zizindikiro zonse zikuwonetsedwa, ndipo chizindikiro chowonetseranso ndi 2.75V. Panthawiyi, mphamvu yoyezera pamalo B ndi 2.75 + 2.75 = 5.5V.

Kusinkhasinkha kwachiwiri: 2.75V yowonetsera magetsi imabwerera ku point A, kulepheretsa kumasintha kuchoka pa 50 ohms kupita ku 10 ohms, kusinkhasinkha koyipa kumachitika, voteji yomwe imawonekera pamalo A ndi -1.83V, voteji imafika pamalo B, ndipo kuwunikira kumachitikanso, ndipo magetsi owonetseredwa ndi -1.83 V. Panthawiyi, mphamvu yowonongeka pamtunda B ndi 5.5-1.83-1.83 = 1.84V.

Kuwunikira kwachitatu: Mphamvu ya -1.83V yowonetsedwa kuchokera pamalo B imafika pamalo A, ndipo mawonekedwe oyipa amabweranso, ndipo mphamvu yowonetsera ndi 1.22V. Mphamvu yamagetsi ikafika pamalo B, kuwunikira pafupipafupi kumachitikanso, ndipo mphamvu yowonekera ndi 1.22V. Panthawiyi, mphamvu yoyezera pamalo B ndi 1.84 + 1.22 + 1.22 = 4.28V.

Pakuzungulira uku, magetsi owoneka bwino amabwerera mmbuyo ndi mtsogolo pakati pa point A ndi point B, zomwe zimapangitsa kuti voteji pamalo B kukhala osakhazikika. Yang’anirani voteji pamalo B: 5.5V-> 1.84V-> 4.28V->……, zitha kuwoneka kuti voteji pamalo B amasinthasintha m’mwamba ndi pansi, komwe kuli kulira kwa siginecha.

Kodi kulira kwa siginecha mu dera la PCB kumachitika bwanji?

Chomwe chimayambitsa kulira kwazizindikiro kumayambitsidwa ndi kusinkhasinkha koyipa, ndipo wolakwira akadali kusintha kwa impedance, komwe kumakhalanso impedance! Mukamawerenga nkhani za kukhulupirika kwa ma sign, nthawi zonse samalani ndi zovuta za impedance.

Kulira kwa chizindikiro kumapeto kwa katundu kudzasokoneza kwambiri kulandila kwa chizindikiro ndikuyambitsa zolakwika zamalingaliro, zomwe ziyenera kuchepetsedwa kapena kuchotsedwa. Chifukwa chake, kuyimitsa kofananira kwa impedance kuyenera kuchitidwa pamizere yayitali yopatsira.