Tus naj npawb ntawm cov kws tsim qauv digital thiab cov kws tshaj lij digital circuit board tsim cov kws tshaj lij hauv kev tsim vaj tsev yog nce ntxiv, uas qhia txog txoj kev loj hlob ntawm kev lag luam. Txawm hais tias qhov tseem ceeb ntawm kev tsim digital tau ua rau muaj kev txhim kho loj hauv cov khoom siv hluav taws xob, nws tseem muaj, thiab yuav muaj qee qhov kev tsim hluav taws xob uas cuam tshuam nrog cov khoom siv hluav taws xob lossis qhov chaw tiag tiag. Cov tswv yim xaim hluav taws xob hauv thaj chaw analog thiab digital muaj qee qhov zoo sib xws, tab sis thaum koj xav kom tau txais txiaj ntsig zoo dua, vim tias lawv cov tswv yim sib txawv ntawm kev sib txuas, kev tsim hluav taws xob yooj yim tsis yog qhov kev daws teeb meem zoo tshaj plaws.

Kab lus no tham txog qhov zoo sib xws thiab qhov sib txawv ntawm kev sib txuas thiab cov xov tooj digital nyob rau hauv cov nqe lus ntawm bypass capacitors, cov khoom siv hluav taws xob, kev tsim hauv av, qhov tsis raug voltage, thiab electromagnetic cuam tshuam (EMI) tshwm sim los ntawm PCB thaiv.

Tus naj npawb ntawm cov kws tsim qauv digital thiab cov kws tshaj lij digital circuit board tsim cov kws tshaj lij hauv kev tsim vaj tsev yog nce ntxiv, uas qhia txog txoj kev loj hlob ntawm kev lag luam. Txawm hais tias qhov tseem ceeb ntawm kev tsim digital tau ua rau muaj kev txhim kho loj hauv cov khoom siv hluav taws xob, nws tseem muaj, thiab yuav muaj qee qhov kev tsim hluav taws xob uas cuam tshuam nrog cov khoom siv hluav taws xob lossis qhov chaw tiag tiag. Cov tswv yim xaim hluav taws xob hauv thaj chaw analog thiab digital muaj qee qhov zoo sib xws, tab sis thaum koj xav kom tau txais txiaj ntsig zoo dua, vim tias lawv cov tswv yim sib txawv ntawm kev sib txuas, kev tsim hluav taws xob yooj yim tsis yog qhov kev daws teeb meem zoo tshaj plaws.

Kab lus no tham txog qhov zoo sib xws thiab qhov sib txawv ntawm kev sib txuas thiab cov xov tooj digital nyob rau hauv cov nqe lus ntawm bypass capacitors, cov khoom siv hluav taws xob, kev tsim hauv av, qhov tsis raug voltage, thiab electromagnetic cuam tshuam (EMI) tshwm sim los ntawm PCB thaiv.

Ntxiv bypass lossis decoupling capacitors ntawm lub rooj tsavxwm Circuit Court thiab qhov chaw ntawm cov capacitors ntawm lub rooj tsavxwm yog qhov kev nkag siab zoo rau cov qauv digital thiab analog. Tab sis nthuav, cov laj thawj sib txawv.

Hauv kev tsim cov kab hluav taws xob analog, bypass capacitors feem ntau yog siv los hla cov teeb liab siab zaus ntawm lub zog hluav taws xob. Yog hais tias bypass capacitors tsis tau ntxiv, cov teeb liab siab zaus no tuaj yeem nkag mus rau cov khoom siv analog rhiab heev los ntawm lub hwj huam mov pins. Feem ntau hais lus, qhov zaus ntawm cov teeb liab siab zaus tshaj qhov muaj peev xwm ntawm cov khoom siv analog los txwv cov teeb liab siab. Yog hais tias lub bypass capacitor tsis siv nyob rau hauv lub analog Circuit Court, lub suab nrov tej zaum yuav qhia nyob rau hauv lub teeb liab txoj kev, thiab nyob rau hauv cov teeb meem loj dua, nws yuav txawm ua rau kev co.

Nyob rau hauv analog thiab digital PCB tsim, bypass lossis decoupling capacitors (0.1uF) yuav tsum muab tso rau ze rau lub cuab yeej li sai tau. Lub hwj huam mov decoupling capacitor (10uF) yuav tsum tau muab tso rau ntawm lub hwj chim kab nkag ntawm lub rooj tsav xwm Circuit Court. Nyob rau hauv txhua rooj plaub, lub pins ntawm cov capacitors yuav tsum luv luv.

Nyob rau hauv lub rooj tsavxwm hauv daim duab 2, cov kev sib txawv yog siv los ua cov kab hluav taws xob thiab hauv av. Vim qhov kev koom tes tsis tsim nyog no, cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob ntawm lub rooj tsav xwm hauv Circuit Court feem ntau yuav raug cuam tshuam los ntawm electromagnetic cuam tshuam.

Nyob rau hauv ib lub vaj huam sib luag ntawm daim duab 3, lub hwj chim thiab hauv av xaim rau cov khoom ntawm lub rooj tsav xwm Circuit Court yog nyob ze rau ib leeg. Qhov sib piv ntawm cov kab hluav taws xob thiab cov kab hauv av hauv lub rooj tsav xwm Circuit Court no yog tsim nyog raws li qhia hauv daim duab 2. Qhov tshwm sim ntawm cov khoom siv hluav taws xob thiab cov khoom siv hluav taws xob hauv Circuit Board raug cuam tshuam los ntawm electromagnetic cuam tshuam (EMI) yog txo los ntawm 679/12.8 zaug lossis cav 54x.
　　
Rau cov khoom siv digital xws li controllers thiab processors, decoupling capacitors kuj xav tau, tab sis rau ntau yam. Ib txoj haujlwm ntawm cov capacitors no yog ua raws li "cov nyiaj me me" them nyiaj.

Hauv cov kab hluav taws xob digital, feem ntau yuav tsum muaj tam sim no los ua lub rooj vag xeev hloov. Txij li thaum hloov pauv tam sim no raug tsim tawm ntawm lub nti thaum hloov thiab ntws los ntawm lub rooj tsav xwm hauv Circuit Court, nws yog qhov zoo kom muaj cov nqi ntxiv "sparre". Yog tias tsis muaj nqi txaus thaum ua qhov kev hloov pauv, lub zog hluav taws xob yuav hloov pauv ntau heev. Kev hloov hluav taws xob ntau dhau yuav ua rau theem teeb liab digital nkag mus rau hauv lub xeev tsis meej, thiab tuaj yeem ua rau lub xeev lub tshuab hauv cov cuab yeej digital ua haujlwm tsis raug.

Qhov hloov pauv tam sim no ntws los ntawm cov kab hluav taws xob hauv Circuit Court yuav ua rau lub zog hloov pauv, thiab cov kab hluav taws xob hluav taws xob muaj cov kab mob parasitic inductance. Cov qauv hauv qab no tuaj yeem siv los xam qhov hloov pauv voltage: V = LdI / dt. Ntawm lawv: V = voltage hloov, L = Circuit Court board kab inductance, dI = tam sim no hloov los ntawm kab, dt = tam sim no hloov lub sij hawm.
　　
Yog li ntawd, rau ntau yam, nws yog qhov zoo dua los thov bypass (los yog decoupling) capacitors ntawm lub hwj chim mov los yog ntawm lub hwj chim mov pins ntawm cov khoom siv nquag.

Cov hlua hluav taws xob thiab cov xaim hauv av yuav tsum tau sib txuas ua ke

Txoj hauj lwm ntawm cov hlua hluav taws xob thiab cov xaim hauv av tau zoo sib xws kom txo tau qhov cuam tshuam ntawm electromagnetic cuam tshuam. Yog tias cov kab hluav taws xob thiab cov kab hauv av tsis zoo sib xws, lub voj kaw lus yuav raug tsim thiab lub suab nrov yuav raug tsim.

Ib qho piv txwv ntawm kev tsim PCB qhov twg cov kab hluav taws xob thiab cov kab hauv av tsis zoo sib xws yog qhia hauv daim duab 2. Ntawm lub rooj tsav xwm Circuit Court no, lub voj voog tsim yog 697cm². Siv cov qauv qhia hauv daim duab 3, qhov muaj peev xwm ntawm cov suab nrov nrov ntawm lossis tawm ntawm lub rooj tsav xwm Circuit Court inducing voltage hauv lub voj yuav txo tau zoo heev.

Qhov sib txawv ntawm cov tswv yim analog thiab digital thaiv cov tswv yim

▍ Lub dav hlau hauv av yog teeb meem

Cov kev paub yooj yim ntawm Circuit Court board thaiv muaj feem xyuam rau ob qho tib si analog thiab digital circuits. Ib txoj cai tseem ceeb ntawm tus ntiv tes xoo yog siv lub dav hlau hauv av tsis cuam tshuam. Qhov kev nkag siab zoo no txo ​​cov dI / dt (hloov tam sim no nrog lub sijhawm) cov txiaj ntsig hauv digital circuits, uas hloov lub peev xwm hauv av thiab ua rau lub suab nrov nkag mus rau hauv analog circuits.

Cov txheej txheem xaim rau digital thiab analog circuits yog qhov zoo ib yam, nrog rau ib qho kev zam. Rau cov analog circuits, muaj lwm qhov yuav tsum tau nco ntsoov, uas yog, khaws cov kab teeb liab digital thiab cov voj voog hauv av kom deb ntawm cov analog circuits li sai tau. Qhov no tuaj yeem ua tiav los ntawm kev sib txuas cov dav hlau hauv av analog rau qhov system hauv av sib txuas sib cais, lossis muab cov analog Circuit Court nyob deb kawg ntawm lub rooj tsav xwm Circuit Court, uas yog qhov kawg ntawm kab. Qhov no yog ua kom muaj kev cuam tshuam sab nraud ntawm txoj kev teeb liab mus rau qhov tsawg kawg nkaus.

Tsis tas yuav ua qhov no rau digital circuits, uas tuaj yeem zam lub suab nrov ntawm lub dav hlau hauv av yam tsis muaj teeb meem.

Daim duab 4 (sab laug) cais cov kev hloov pauv digital los ntawm analog circuit thiab cais cov digital thiab analog seem ntawm Circuit Court. (Txoj cai) Qhov siab zaus thiab qis zaus yuav tsum tau sib cais kom ntau li ntau tau, thiab cov khoom siv ntau zaus yuav tsum nyob ze rau cov khoom siv hluav taws xob sib txuas.

Daim duab 5 Layout ob txoj kab ze ntawm PCB, nws yooj yim los tsim cov kab mob cab. Vim muaj qhov muaj peev xwm zoo li no, kev hloov pauv sai ntawm ib txoj kab tuaj yeem tsim cov teeb liab tam sim no ntawm lwm txoj kab.

Daim duab 6 Yog tias koj tsis xyuam xim rau qhov chaw ntawm qhov chaw, cov kab hauv PCB tuaj yeem tsim kab inductance thiab kev sib nrig sib inductance. Cov kab mob parasitic inductance no muaj kev phom sij heev rau kev ua haujlwm ntawm circuits nrog rau digital switching circuits.

▍ Qhov chaw nyob

Raws li tau hais los saum toj no, hauv txhua tus qauv PCB, lub suab nrov ntawm Circuit Court thiab "tsim" ntu (tsis muaj suab nrov) yuav tsum tau sib cais. Feem ntau hais lus, digital circuits yog "nplua nuj" nyob rau hauv lub suab nrov thiab tsis hnov ​​​​tsw rau lub suab nrov (vim tias cov circuits digital muaj lub suab nrov loj dua); Ntawm qhov tsis sib xws, qhov voltage suab kam rau ntawm analog circuits yog me dua.

Ntawm ob, analog circuits yog qhov nkag siab tshaj plaws rau kev hloov suab nrov. Hauv kev xaim hluav taws xob sib xyaw ua ke, ob lub voj voog no yuav tsum tau sib cais, raws li pom hauv daim duab 4.
　　
▍ Parasitic Cheebtsam tsim los ntawm PCB tsim

Ob lub ntsiab parasitic uas yuav ua rau muaj teeb meem tau yooj yim tsim hauv PCB tsim: parasitic capacitance thiab parasitic inductance.

Thaum tsim ib lub rooj tsav xwm hauv Circuit Court, tso ob txoj kab nyob ze rau ib leeg yuav ua rau cov kab mob parasitic capacitance. Koj tuaj yeem ua qhov no: Ntawm ob txheej txheej sib txawv, tso ib kab rau saum lwm txoj kab; los yog nyob rau tib txheej, tso ib kab ntawm ib sab ntawm lwm txoj kab, raws li pom hauv daim duab 5.
　　
Hauv ob txoj kab kev teeb tsa no, kev hloov pauv ntawm qhov hluav taws xob dhau sijhawm (dV / dt) ntawm ib txoj kab yuav ua rau tam sim no ntawm lwm txoj kab. Yog hais tias lwm cov kab yog siab impedance, tam sim no generated los ntawm hluav taws xob teb yuav hloov mus rau hauv voltage.
　　
Fast voltage transients feem ntau tshwm sim nyob rau sab digital ntawm analog teeb liab tsim. Yog hais tias cov kab nrog ceev voltage transients nyob ze rau high-impedance analog traces, qhov yuam kev no yuav cuam tshuam rau qhov tseeb ntawm cov analog circuits. Nyob rau hauv ib puag ncig no, analog circuits muaj ob qhov tsis zoo: lawv qhov kev ua siab ntev lub suab qis dua li ntawm cov circuits digital; thiab siab impedance kab yog ntau dua.
　　
Siv ib qho ntawm ob txoj kev hauv qab no tuaj yeem txo qhov tshwm sim no. Cov txheej txheem siv ntau tshaj plaws yog hloov qhov loj ntawm cov kab raws li qhov sib npaug ntawm cov peev txheej. Qhov loj tshaj plaws rau kev hloov pauv yog qhov kev ncua deb ntawm ob kab. Nws yuav tsum tau muab sau tseg tias qhov sib txawv d yog nyob rau hauv lub denominator ntawm lub capacitance equation. Raws li d nce, lub capacitive reactance yuav txo. Lwm qhov sib txawv uas tuaj yeem hloov tau yog qhov ntev ntawm ob txoj kab. Nyob rau hauv cov ntaub ntawv no, qhov ntev L txo, thiab lub capacitive reactance ntawm ob kab kuj yuav txo.
　　
Lwm cov txheej txheem yog nteg ib qho av xaim ntawm ob kab no. Cov xaim hauv av tsis tshua muaj impedance, thiab ntxiv lwm cov kab zoo li no yuav ua rau tsis muaj zog cuam tshuam hluav taws xob, raws li pom hauv daim duab 5.
　　
Lub hauv paus ntsiab lus ntawm parasitic inductance nyob rau hauv Circuit Court board yog zoo ib yam li cov parasitic capacitance. Nws kuj yog los nteg tawm ob kab. Ntawm ob txheej sib txawv, tso ib kab rau saum lwm txoj kab; los yog nyob rau tib txheej, tso ib kab ib sab ntawm ib sab, raws li qhia hauv daim duab 6.

Nyob rau hauv ob txoj kev teeb tsa no, qhov kev hloov pauv tam sim no (dI / dt) ntawm ib txoj kab nrog lub sijhawm, vim yog qhov inductance ntawm cov kab no, yuav tsim qhov voltage ntawm tib txoj kab; thiab vim muaj kev sib nrig sib inductance, nws yuav A proportional tam sim no generated rau lwm txoj kab. Yog tias qhov hloov pauv voltage ntawm thawj kab yog qhov loj txaus, kev cuam tshuam yuav txo qhov voltage kam rau ntawm lub digital circuit thiab ua rau yuam kev. Qhov tshwm sim no tsis yog tshwm sim hauv digital circuits xwb, tab sis qhov tshwm sim no muaj ntau dua hauv cov circuits digital vim tias qhov hloov pauv tam sim no loj hauv digital circuits.
　　
Txhawm rau tshem tawm cov suab nrov los ntawm cov khoom siv hluav taws xob cuam tshuam, nws yog qhov zoo tshaj los cais cov kab " ntsiag to" los ntawm cov suab nrov I / O cov chaw nres nkoj. Txhawm rau kom ua tiav lub zog qis impedance thiab hauv av network, qhov inductance ntawm cov xov hluav taws xob digital yuav tsum raug txo kom tsawg, thiab cov capacitive coupling ntawm analog circuits yuav tsum raug txo kom tsawg.
　　
03

Xaus

Tom qab qhov kev txiav txim siab ntawm cov digital thiab analog, kev ceev ceev yog qhov tseem ceeb rau kev ua tiav PCB. Cov tswv yim xaim feem ntau yog qhia rau txhua tus neeg raws li txoj cai ntawm tus ntiv tes xoo, vim tias nws nyuaj rau kev sim qhov kawg ntawm cov khoom lag luam hauv ib puag ncig kev sim. Yog li ntawd, txawm hais tias qhov zoo sib xws hauv cov tswv yim xaim ntawm cov digital thiab analog circuits, qhov sib txawv ntawm lawv cov tswv yim thaiv yuav tsum raug lees paub thiab ua tib zoo.