Kanthi nambah kacepetan ngoper output sirkuit integral lan Papan PCB density, Signal Integrity has become one of the issues that must be concerned in high-speed digital PCB design. The parameters of components and PCB board, the layout of components on PCB board, the wiring of high-speed Signal line and other factors, Can cause problems with signal integrity.

For PCB layouts, signal integrity requires a board layout that does not affect signal timing or voltage, while for circuit wiring, signal integrity requires termination elements, layout strategies, and wiring information. Kacepetan sinyal dhuwur ing PCB, panggonan sing salah saka komponen pungkasan, utawa kabel sing salah saka sinyal kacepetan dhuwur bisa nyebabake masalah integritas sinyal, sing bisa nyebabake sistem ngasilake data sing salah, sirkuit bisa digunakake kanthi ora bener utawa ora bisa digunakake. How to take signal integrity into full consideration and take effective control measures in PCB design has become a hot topic in PCB design industry.

Signal integrity Problem Good signal integrity means that the signal can respond with the correct timing and voltage level values when required. Kosok baline, nalika sinyal ora nanggapi kanthi bener, ana masalah integritas sinyal. Masalah integritas sinyal bisa nyebabake utawa langsung nyebabake distorsi sinyal, kesalahan wektu, data sing salah, alamat lan garis kontrol, lan kesalahan sistem, utawa uga sistem crash. Ing proses praktik desain PCB, masarakat wis nglumpukake akeh aturan desain PCB. Ing desain PCB, integritas sinyal PCB bisa digayuh kanthi luwih tliti kanthi ngrujuk marang aturan desain kasebut.

When designing PCB, we should first understand the design information of the whole circuit board, which mainly includes:

1. The number of devices, device size, device package, chip rate, whether PCB is divided into low speed, medium speed and high speed area, which is the interface input and output area;

2. The overall layout requirements, device layout location, whether there is a high power device, chip device heat dissipation special requirements;

3. Jinis garis sinyal, kacepetan lan arah transmisi, syarat kontrol impedansi garis sinyal, arah kacepetan bis lan kahanan nyopir, sinyal kunci lan langkah-langkah perlindungan;

4. Jinis sumber daya, jinis lemah, syarat toleransi gangguan kanggo sumber daya lan lemah, setelan lan segmentasi sumber daya lan bidang lemah;

5. Jinis lan tarif garis jam, sumber lan arah garis jam, syarat wektu tundha jam, syarat baris paling dawa.

Desain berlapis PCB

Sawise ngerti informasi dhasar papan sirkuit, kudu nimbang persyaratan desain biaya sirkuit lan integritas sinyal, lan pilih sawetara lapisan kabel sing cukup. At present, the circuit board has gradually developed from single layer, double layer and four layer to more multi-layer circuit board. Multi-layer PCB design can improve the reference surface of signal routing and provide backflow path for signal, which is the main measure to achieve good signal integrity. When designing PCB layering, follow the following rules:

1. Bidang referensi luwih becik dadi bidang lemah. Both power supply and ground plane can be used as reference plane, and both have certain shielding function. Nanging, efek perisai pesawat suplai listrik luwih murah tinimbang pesawat dhasar amarga impedansi karakteristik sing luwih dhuwur lan beda potensial sing luwih gedhe ing antarane bidang pasokan listrik lan level lemah referensi.

2. Digital circuit and analog circuit are layered. Yen ngidini biaya desain, luwih becik ngatur sirkuit digital lan analog ing lapisan sing beda. If must want to arrange in same wiring layer, can use ditch, add earthing line, the method such as dividing line to remedy. Daya analog lan digital lan lemah kudu dipisahake, aja dicampur.

3. Routing sinyal tombol lapisan jejer ora nyebrang area pamisahan. Sinyal bakal nggawe loop sinyal gedhe ing wilayah kasebut lan ngasilake radiasi sing kuat. If the signal cable must cross the area when the ground cable is divided, a single point can be connected between the ground to form a connection bridge between the two ground points, and then the cable can be routed through the connection bridge.

4. Kudu ana pesawat dhasar sing cukup lengkap ing sangisore permukaan komponen. Integritas pesawat dhasar kudu dijaga nganti adoh kanggo piring multilayer. Ora ana garis sinyal sing biasane diidini mbukak ing pesawat dhasar.

5, frekuensi dhuwur, kacepetan dhuwur, jam lan garis sinyal liyane kudu duwe pesawat dhasar sing jejer. In this way, the distance between signal line and ground line is only the distance between PCB layers, so the actual current always flows in the ground line directly below the signal line, forming the smallest signal loop area and reducing radiation.

How to design the signal of integrity PCB

PCB layout design

Kunci desain integritas sinyal papan cetak yaiku tata letak lan kabel, sing ana gandhengane langsung karo kinerja PCB. Prior to layout, the PCB size must be determined to meet the function at the lowest possible cost. Yen PCB gedhe banget lan disebar, garis transmisi bisa uga dawa banget, saengga bisa nambah impedansi, nyuda resistensi swara, lan nambah biaya. If the components are placed together, heat dissipation is poor, and coupling crosstalk may occur in adjacent wiring. Mula, tata letak kudu didhasarake ing unit fungsional sirkuit, nalika ngelingi kompatibilitas elektromagnetik, disipasi panas lan faktor antarmuka.

Nalika nyedhiyakake PCB kanthi sinyal digital lan analog campuran, aja nyampur sinyal digital lan analog. Yen sinyal analog lan digital kudu dicampur, priksa manawa baris vertikal kanggo nyuda efek kopling. Sirkuit digital, sirkuit analog, lan sirkuit sing ngasilake swara ing papan sirkuit kudu dipisahake, lan sirkuit sensitif kudu dialihake luwih dhisik, lan jalur kopling ing antarane sirkuit kudu diilangi. Utamane, coba pikirake jam, ngreset lan ngganggu, aja salaras karo garis-garis switch saiki, yen gampang rusak sinyal kopling elektromagnetik, nyebabake reset utawa gangguan sing ora dikarepake. The overall layout should follow the following principles:

1. Tata letak partisi fungsional, sirkuit analog lan sirkuit digital ing PCB kudu tata ruang sing beda.

2. Miturut proses sinyal sirkuit kanggo ngatur Unit sirkuit fungsi, supaya aliran sinyal kanggo njaga arah padha.

3. Take the core components of each functional circuit unit as the center, and other components are arranged around it.

4. Shorten the connection between high-frequency components as much as possible and try to reduce their distribution parameters.

5. Easily disturbed components should not be too close to each other, input and output components should be far away.

How to design the signal of integrity PCB

Desain kabel PCB

Kabeh garis sinyal kudu diklasifikasikake sadurunge kabel PCB. First of all, clock line, sensitive signal line, and then high-speed signal line, in order to ensure that this kind of signal through the hole is enough, distribution parameters of good characteristics, and then general unimportant signal line.

Incompatible signal lines should be far away from each other and do not parallel wiring, such as digital and analog, high speed and low speed, high current and small current, high voltage and low voltage. Kabel sinyal ing lapisan sing beda kudu diarahake kanthi vertikal menyang siji liyane kanggo nyuda crosstalk. Susunan garis sinyal paling apik diatur miturut arah aliran sinyal. Garis sinyal output sirkuit ora bisa dilalekake maneh menyang area garis sinyal input. High-speed signal lines should be kept as short as possible to avoid interfering with other signal lines. Ing panel pindho, yen perlu, kabel lemah isolasi bisa ditambahake ing loro-lorone saka garis sinyal kacepetan dhuwur. Kabeh garis jam kanthi kacepetan ing papan multilayer kudu dilindhungi miturut dawa garis jam.

Prinsip umum kabel yaiku:

1. Minangka adoh sabisa kanggo milih desain kabel Kapadhetan kurang, lan kabel sinyal minangka adoh sabisa kekandelan konsisten, kondusif kanggo cocog impedansi. Kanggo sirkuit RF, desain arah garis sinyal, jembaré lan jarak garis sing mokal bisa nyebabake gangguan antar garis transmisi sinyal.

2. Minangka adoh sabisa supaya kabel input lan output jejer lan kabel podo long-distance. Kanggo nyuda crosstalk saka garis sinyal paralel, jarak antarane garis sinyal bisa ditambah, utawa sabuk isolasi bisa dipasang ing antarane garis sinyal.

3. Jembar garis ing PCB kudu seragam lan ora ana mutasi jembar garis. Bend kabel PCB ora nggunakake sudhut 90 derajat, kudu nggunakake busur utawa Sudut 135 derajat, nganti bisa njaga kesinambungan impedansi garis.

4. Minimize the area of the current loop. The external radiation intensity of current-carrying circuit is proportional to the current passing through, the loop area and the square of signal frequency. Reducing the current loop area can reduce the ELECTROMAGNETIC interference of PCB.

5. Minangka adoh sabisa kanggo ngurangi dawa kabel, nambah jembaré kabel, iku kondusif kanggo ngurangi impedansi kabel.

6. Kanggo sinyal kontrol ngalih, jumlah kabel SIGNAL PCB sing ngganti negara ing wektu sing padha kudu suda sabisa.