Hauv PCB tsim, electromagnetic compatibility (EMC) thiab cov cuam tshuam electromagnetic cuam tshuam (EMI) ib txwm muaj ob qho kev mob taub hau loj rau cov engineers, tshwj xeeb tshaj yog nyob rau niaj hnub Circuit Board tsim thiab cov khoom siv txuas ntxiv mus, OEMs xav tau cov tshuab ceev dua.Hauv tsab xov xwm no, kuv yuav qhia txog yuav ua li cas kom tsis txhob muaj teeb meem electromagnetic hauv PCB tsim.
1. Crosstalk thiab kev sib dhos yog qhov ua kom pom tseeb
Alignment yog ib qho tseem ceeb tshwj xeeb los xyuas kom meej qhov zoo ntawm qhov tam sim no.Yog tias qhov tam sim no los ntawm lub oscillator lossis lwm yam khoom siv zoo sib xws, nws yog ib qho tseem ceeb tshwj xeeb uas yuav tsum ua kom cov tam sim no sib cais los ntawm cov txheej hauv av, los yog kom cov tam sim no tsis txhob khiav mus rau qhov sib npaug nrog lwm qhov kev sib dhos.Ob lub teeb liab siab ceev hauv qhov sib npaug tuaj yeem tsim EMC thiab EMI, tshwj xeeb tshaj yog crosstalk.Nws yog ib qho tseem ceeb uas yuav tsum ua kom lub resistor txoj kev luv li sai tau thiab rov qab txoj kev tam sim no kom luv li sai tau.Qhov ntev ntawm txoj kev rov qab yuav tsum yog tib yam li qhov ntev ntawm txoj kev xa mus.
Rau EMI, ib txoj hauv kev hu ua "kev ua txhaum cai" thiab lwm qhov yog "kev raug tsim txom".Inductive thiab capacitive coupling cuam tshuam rau "tus neeg raug tsim txom" txoj hauv kev vim muaj cov khoom siv hluav taws xob, yog li tsim cov dej ntws mus rau pem hauv ntej thiab thim rov qab ntawm "kev raug tsim txom".Nyob rau hauv txoj kev no, ripple yog generated nyob rau hauv ib tug ruaj khov ib puag ncig qhov twg cov kis tau tus mob thiab tau txais lengths ntawm lub teeb liab yuav luag sib npaug.
Nyob rau hauv ib qho chaw zoo sib npaug nrog cov kev sib dhos ruaj khov, cov kev cuam tshuam cuam tshuam yuav tsum thim tawm ib leeg, yog li tshem tawm cov lus sib tham.Txawm li cas los xij, peb nyob hauv lub ntiaj teb uas tsis zoo tag nrho uas tsis muaj qhov zoo li no tshwm sim.Yog li ntawd, peb lub hom phiaj yog tias crosstalk yuav tsum tau khaws cia kom tsawg kawg nkaus rau txhua qhov kev sib tw.Cov nyhuv ntawm crosstalk tuaj yeem txo qis yog tias qhov dav ntawm cov kab sib txuas yog ob npaug ntawm qhov dav ntawm kab.Piv txwv li, yog tias txoj kab dav yog 5 mils, qhov tsawg kawg nkaus ntawm ob kab sib txuas yuav tsum yog 10 mils lossis ntau dua.
Raws li cov ntaub ntawv tshiab thiab cov khoom siv txuas ntxiv tshwm sim, PCB cov neeg tsim khoom yuav tsum tau txuas ntxiv nrog EMC thiab cuam tshuam cov teeb meem.
2. Decoupling capacitor
Decoupling capacitors txo qhov tsis xav tau los ntawm crosstalk.Lawv yuav tsum nyob nruab nrab ntawm lub hwj chim thiab hauv av pins ntawm lub cuab yeej, uas ua kom lub AC impedance qis thiab txo cov suab nrov thiab crosstalk.Txhawm rau kom ua tiav cov impedance qis tshaj qhov ntau zaus, ntau lub decoupling capacitors yuav tsum tau siv.
Lub hauv paus ntsiab lus tseem ceeb rau kev tso decoupling capacitors yog tias lub capacitor nrog tus nqi qis tshaj plaws tau muab tso rau ze rau ntawm lub cuab yeej kom txo tau qhov cuam tshuam inductive ntawm kev sib dhos.Qhov tshwj xeeb capacitor no yuav tsum tau muab tso rau ze li sai tau rau lub cuab yeej lub hwj huam mov pins lossis lub hwj huam mov raceway thiab cov ntaub qhwv ntawm lub capacitor yuav tsum txuas ncaj qha mus rau vias lossis hauv av.Yog tias qhov kev sib tw ntev, siv ntau lub vias kom txo qis hauv av impedance.
3. Grounding lub PCB
Ib txoj hauv kev tseem ceeb los txo EMI yog tsim cov txheej txheem PCB hauv av.Thawj kauj ruam yog ua kom thaj chaw hauv av kom loj li sai tau nyob rau hauv tag nrho cheeb tsam ntawm PCB pawg thawj coj saib kom txo qis emissions, crosstalk thiab suab nrov.Kev saib xyuas tshwj xeeb yuav tsum tau ua thaum txuas txhua qhov txuas mus rau hauv av taw tes lossis txheej hauv av, yam tsis muaj qhov cuam tshuam nruab nrab ntawm cov txheej txheej hauv av tsis tuaj yeem siv tag nrho.
Ib qho tshwj xeeb PCB tsim muaj ntau qhov ruaj khov voltages.Qhov zoo tshaj plaws, txhua qhov siv hluav taws xob muaj nws tus kheej cov txheej txheem hauv av.Txawm li cas los xij, ntau txheej txheej hauv av yuav ua rau cov nqi tsim khoom ntawm PCB thiab ua rau nws kim heev.Ib qho kev sib haum xeeb yog siv cov txheej hauv av hauv peb mus rau tsib qhov chaw sib txawv, txhua qhov tuaj yeem muaj ntau qhov chaw hauv av.Qhov no tsis tsuas yog tswj cov nqi tsim khoom ntawm lub rooj tsavxwm, tab sis kuj txo EMI thiab EMC.
Qhov qis impedance grounding system tseem ceeb yog tias EMC yuav tsum tau txo qis.Nyob rau hauv ib tug multilayer PCB nws yog ib qhov zoo dua kom muaj ib tug txhim khu kev qha grounding txheej es tsis yog ib tug tooj liab tshuav thaiv (tooj liab thieving) los yog ib tug tawg txheej av vim nws muaj impedance uas tsis muaj impedance, muab ib tug tam sim no txoj kev thiab yog qhov zoo tshaj plaws qhov chaw ntawm rov qab cov teeb liab.
Qhov ntev ntawm lub teeb liab yuav siv sij hawm rov qab los rau hauv av kuj tseem ceeb heev.Lub sijhawm siv lub teeb liab mus rau thiab los ntawm qhov chaw yuav tsum sib piv, txwv tsis pub muaj qhov tshwm sim zoo li tus kav hlau txais xov yuav tshwm sim, tso cai rau lub zog hluav taws xob los ua ib feem ntawm EMI.Ib yam li ntawd, qhov kev sib raug zoo ntawm qhov tam sim no mus rau / los ntawm lub teeb liab yuav tsum luv li sai tau, yog tias qhov chaw thiab cov kev rov qab los tsis yog qhov sib npaug, qhov av yuav tshwm sim thiab qhov no tseem yuav tsim EMI.
4. Zam lub kaum sab xis 90 °
Txhawm rau txo EMI, kev sib dhos, vias thiab lwm yam khoom yuav tsum raug zam kom tsim lub kaum sab xis 90 °, vim tias lub kaum sab xis yuav tsim hluav taws xob.Txhawm rau kom tsis txhob 90 ° lub kaum sab xis, qhov kev sib dhos yuav tsum yog tsawg kawg yog ob 45 ° lub kaum sab xis ntawm lub kaum sab xis.
5. Kev siv ntau tshaj qhov yuav tsum tau ceev faj
Hauv yuav luag tag nrho cov PCB layouts, vias yuav tsum tau siv los muab kev sib txuas ntawm cov txheej txheem sib txawv.Qee qhov xwm txheej, lawv kuj tsim cov kev xav, raws li cov yam ntxwv impedance hloov thaum lub vias raug tsim nyob rau hauv kev sib dhos.
Nws tseem yog ib qho tseem ceeb uas yuav tsum nco ntsoov tias vias nce qhov ntev ntawm qhov kev sib tw thiab yuav tsum tau ua kom haum.Nyob rau hauv cov ntaub ntawv ntawm kev sib txawv alignments, vias yuav tsum tau zam yog tias ua tau.Yog tias qhov no tsis tuaj yeem zam tau, vias yuav tsum tau siv rau hauv ob qho tib si kev sib dhos kom them nyiaj rau kev ncua ntawm lub teeb liab thiab rov qab txoj hauv kev.
6. Cables thiab tiv thaiv lub cev
Cables nqa digital circuits thiab analogue tam sim no tuaj yeem tsim cov kab mob parasitic capacitance thiab inductance, ua rau muaj ntau yam teeb meem ntawm EMC.Yog tias siv cov kab sib tw twisted, qib qis ntawm kev sib txuas yog khaws cia thiab cov hlau nplaum tsim tawm raug tshem tawm.Rau cov teeb liab ntau zaus, cov kab hluav taws xob tiv thaiv yuav tsum tau siv, nrog rau ob qho tib si pem hauv ntej thiab nraub qaum, txhawm rau tshem tawm EMI cuam tshuam.
Kev tiv thaiv lub cev yog qhov thaiv tag nrho lossis ib feem ntawm lub kaw lus hauv pob hlau los tiv thaiv EMI los ntawm kev nkag mus rau PCB circuitry.Qhov kev tiv thaiv no ua haujlwm zoo li lub kaw lus kaw, hauv av-ua capacitor, txo qhov loj ntawm lub kav hlau txais xov voj thiab nqus EMI.
Post lub sij hawm: Nov-23-2022