Nthawi zambiri, PCB Kulumikizana kudutsa m’mabowo, mapadi oyeserera, zingwe zazifupi, ndi zina zambiri, zomwe zimakhala ndi parasitic capacitance, zomwe zimakhudza chizindikirocho. Mphamvu ya capacitance pachizindikiro iyenera kusanthulidwa kuchokera kumapeto ndikufika kumapeto, ndipo imakhudza poyambira komanso kumapeto.

Choyamba dinani kuti muwone momwe zingakhudzire wotumizira. Chizindikiro chokwera mofulumira chikamafika pa capacitor, capacitor imalipidwa mwachangu. Kutsitsa kwapano kumakhudzana ndi kuthamanga kwamphamvu kwamagetsi. Njira yoyikira pakali pano ndi: I = C * dV / dt. Kutalika kwa capacitance, kukweza kwamphamvu kwamakono, kuthamanga kwanthawi yayitali kwazizindikiro, ndi dt yaying’ono, kumathandizanso kuti pakhale chiwongolero chamakono.

Tikudziwa kuti kuwunika kwa siginecha kumakhudzana ndikusintha kwakanthawi komwe chizindikirocho chimazindikira, kotero kuti tiwunikenso, tiyeni tiwone kusintha kwakanthawi komwe mphamvu yamphamvu imayambitsa. Pachiyambi choyamba cha kukweza kwa capacitor, impedance imafotokozedwa ngati:

Apa, dV kwenikweni ndi kusintha kwamphamvu kwamagetsi panjira, dt ndiye nthawi yakukwera kwa siginolo, ndipo chilinganizo cha impedance ya capacitance chimakhala:

Kuchokera pa njirayi, titha kupeza chidziwitso chofunikira kwambiri, pomwe chizindikirocho chimagwiritsidwa ntchito koyambirira kumapeto onse a capacitor, impedance ya capacitor imakhudzana ndi nthawi yakukwera kwachizindikiro ndi kuthekera kwake.

Kawirikawiri pa gawo loyambirira la kukweza kwa capacitor, impedance imakhala yaying’ono kwambiri, yocheperako poyerekeza ndi mawonekedwe amagetsi. Kuwonetsa kolakwika kwa chizindikirocho kumachitika pa capacitor, ndipo siginidwe yoyipa yamagetsi imakwezedwa ndi siginecha yoyambirira, zomwe zimapangitsa kutsika kwa chizindikirocho pa transmitter komanso chosagwirizana ndi chizindikirocho pa transmitter.

Pakumapeto kolandila, chizindikirocho chitafika pakulandila, kuwunika koyenera kumachitika, chizindikirocho chimawonekera pa capacitor, mawonekedwe amtunduwu amachitika, ndipo magetsi osinkhasinkha amawonanso kumapeto kuti alandire amachititsanso chizindikirocho kulandira end kuti apange kutsika.

Kuti phokoso lowonetsedwa likhale lochepera 5% yamagetsi oyenda, omwe amalekerera chizindikirocho, kusintha kwa impedance kuyenera kukhala kochepera 10%. Ndiye kodi capacitorance impedance iyenera kukhala yotani? Capacitance impedance ndi impedance yofananira, ndipo titha kugwiritsa ntchito njira yofananira ya impedance ndikuwonetsa chilinganizo chokwanira pozindikira kukula kwake. Chifukwa cha impedance yofananayo, tikufuna kuti capacitance impedance ikhale yayikulu momwe ingathere. Kungoganiza kuti capacitance impedance ndi K nthawi ya PCB wiring yodziwika bwino ya impedance, impedance yomwe imamvekedwa ndi chizindikiritso cha capacitor itha kupezeka molingana ndi njira yofananira ya impedance:

Ndiye kuti, malinga ndi kuwerengera koyenera kumeneku, kutayika kwa capacitor kuyenera kukhala kasanu ndi kawiri kupindika kwa PCB. M’malo mwake, momwe ma capacitor amalipiritsidwira, kutsekemera kwa capacitor kumawonjezeka ndipo sikumangokhala impedance yotsika kwambiri nthawi zonse. Kuphatikiza apo, chida chilichonse chimatha kukhala ndi vuto loyambitsa matendawa, lomwe limakulitsa kuyimitsidwa. Chifukwa chake malire okwanira asanu ndi anayiwa amatha kumasuka. Pokambirana zotsatirazi, ganizirani kuti malirewo ndi kasanu.

Ndi chizindikiritso cha impedance, titha kudziwa kuchuluka kwa ma capacitance omwe angalekerere. Makonda a 50 ohms pa board board ndiofala kwambiri, kotero ndimagwiritsa ntchito 50 ohms kuti ndiwerenge.

Zatsimikizika kuti:

Poterepa, ngati nthawi yakukwera ndi 1ns, capacitance imakhala yochepera ma 4 picograms. Mofananamo, ngati capacitance ndi ma 4 picograms, nthawi yokwera ndi 1ns yabwino kwambiri. Ngati nthawi yakukwera ndi ma 0.5ns, makanema 4 awa amatha kubweretsa mavuto.

Kuwerengetsa pano ndikungofotokozera zakukhudzidwa kwa ma capacitance, dera lenileni ndilovuta kwambiri, palinso zifukwa zina zofunika kuziganizira, ngati kuwerengera kumeneku sikolondola sikothandiza kwenikweni. Chofunikira ndikumvetsetsa momwe capacitance imakhudzira chizindikirochi powerengera. Tikamvetsetsa za momwe zinthu zimakhudzira gulu la dera, titha kupereka chitsogozo pakupanga ndikudziwa momwe tingawunikire mavuto akachitika. Kulingalira kolondola kumafuna kutsanzira mapulogalamu.

Kutsiliza:

1. Katundu wa capacitive panthawi ya PCB routing amachititsa kuti ma sign a kumapeto kwa transmitter apange kutulutsa, ndipo chizindikiritso cha wolandila chimatulutsanso kutsika.

2. kulolerana kwa capacitance kumakhudzana ndi nthawi yakukwera kwachizindikiro, kuthamanga kwa nthawi yayitali, kuchepa kwa kulolera.