Ngokukhula kwesivinini sokushintsha kokuphuma kwesifunda esididiyelwe kanye PCB ibhodi 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. Isivinini sesignali esiphezulu ku-PCB, ukubekwa okungalungile kwezingxenye zokugcina, noma izintambo ezingalungile zamasignali anesivinini esiphezulu kungabangela izinkinga zesignali yobuqotho, okungabangela isistimu ukuthi ikhiphe idatha engalungile, isekethe isebenze ngendlela engafanele noma ingasebenzi nhlobo. Ungabuthathela kanjani ubuqotho besiginali ekucabangeni okugcwele futhi uthathe izinyathelo zokulawula ezisebenzayo ekwakhiweni kwe-PCB sekuyisihloko esishisayo embonini yokuklama ye-PCB.

Signal integrity Problem Good signal integrity means that the signal can respond with the correct timing and voltage level values when required. Ngakolunye uhlangothi, lapho isignali ingaphenduli kahle, kunenkinga yobuqotho besiginali. Izinkinga zobuqotho besiginali zingaholela noma ziholele ngqo ekuhlanekezelweni kwesiginali, amaphutha wesikhathi, idatha engalungile, amakheli nezindlela zokulawula, nokungasebenzi kahle kohlelo, noma ngisho nokuwohloka kwesistimu. Enqubweni ye-PCB design practice, abantu baqongelele imithetho eminingi yokuklama ye-PCB. Ekwakhiweni kwe-PCB, ubuqotho besignali ye-PCB bungafinyelelwa kangcono ngokubhekisela ngokucophelela kule mithetho yokuklama.

Lapho kuklanywa i-PCB, kufanele siqale siqonde imininingwane yokuqanjwa kwebhodi lonke lesifunda, okubandakanya ikakhulu:

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. Uhlobo lwentambo yesiginali, isivinini kanye nokuqondisa kokuhambisa, izidingo zokulawulwa kwe-impedance kolayini wesiginali, isiqondiso sejubane lebhasi nesimo sokushayela, amasiginali abalulekile nezinyathelo zokuvikela;

4. Uhlobo lokuphakelwa kukagesi, uhlobo lomhlabathi, izidingo zokubekezelela umsindo ngokuphakelwa kukagesi nomhlabathi, ukusetha kanye nokuhlukaniswa kokuphakelwa kukagesi kanye nendiza yaphansi;

5. Izinhlobo namazinga emigqa yewashi, umthombo nesiqondiso semigqa yewashi, izimfuneko zokulibaziseka kwewashi, izimfuneko zolayini omude kakhulu.

PCB egqinsiwe design

Ngemuva kokuqonda imininingwane eyisisekelo yebhodi lesifunda, kuyadingeka ukukala izidingo zokuklanywa kwezindleko zebhodi lesifunda kanye nobuqotho besiginali, bese ukhetha inani elifanele lezendlalelo zezintambo. 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. Indiza eyinkomba kufanele kube yindiza yaphansi. Kokubili ukunikezwa kwamandla kanye nendiza yaphansi kungasetshenziswa njengendiza eyinkomba, futhi kokubili kunomsebenzi othile wokuvikela. Kodwa-ke, umthelela wokuvikela wendiza yokuphakela amandla uphansi kakhulu kunalowo wendiza yaphansi ngenxa yesici sayo esiphezulu kanye nomehluko omkhulu ongaba khona phakathi kwendiza yokuphakela amandla kanye nezinga eliphansi lereferensi.

2. Digital circuit and analog circuit are layered. Lapho izindleko zokuklama zivuma, kungcono ukuhlela amasekhethi edijithali kanye ne-analogi ezendlalelo ezihlukene. If must want to arrange in same wiring layer, can use ditch, add earthing line, the method such as dividing line to remedy. Amandla we-analog ne-digital kanye nomhlabathi kumele kuhlukaniswe, kungalokothi kuhlanganiswe.

3. Umzila wokhiye wesiginali wezendlalelo eziseduze awudluli indawo yokuhlukaniswa. Amasignali azokwakha iluphu yesiginali enkulu esifundeni futhi akhiqize imisebe enamandla. 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. Kufanele kube khona indiza yasemhlabeni eqediwe ngokuphelele engaphansi kwendawo yengxenye. Ubuqotho bendiza yaphansi kufanele bugcinwe ngokusemandleni epuleti le-multilayer. Azikho imigqa yamasignali ngokuvamile evunyelwe ukusebenza endizeni yaphansi.

I-5, imvamisa ephezulu, isivinini esikhulu, iwashi neminye imigqa yesiginali ebalulekile kufanele ibe nendiza yaphansi eseduze. 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

Isihluthulelo sedizayini yobuqotho besignali yebhodi eliphrintiwe ukwakheka kanye nezintambo, okuhlobene ngokuqondile nokusebenza kwe-PCB. Prior to layout, the PCB size must be determined to meet the function at the lowest possible cost. Uma i-PCB inkulu kakhulu futhi isatshalaliswa, ulayini wokudlulisa ungaba mude kakhulu, okuholele ekukhuphukeni kwe-impedance, kunciphise ukumelana nomsindo, nezindleko ezinyukile. Uma izingxenye zibekwe ndawonye, ​​ukushabalalisa ukushisa akulungile, futhi ukuhlanganisa i-crosstalk kungenzeka ku-wiring eseduze. Ngakho-ke, ukwakheka kufanele kususelwe kumayunithi wokusebenza wesekethe, ngenkathi kubhekwa ukuhambisana kwe-electromagnetic, ukushabalalisa ukushisa kanye nezici zesixhumi esibonakalayo.

Uma ubeka i-PCB enezinombolo ezixubile zedijithali ne-analog, ungahlanganisi amasignali edijithali nawe-analog. Uma ngabe amasiginali we-analog nedijithali kumele axutshwe, qiniseka ukuthi ulayini uqonde ukuze unciphise umphumela wokuhlanganisa okuwela phakathi. Isekhethi yedijithali, isekethe ye-analog, kanye nesekethe edala umsindo ebhodini lesifunda kufanele ihlukaniswe, futhi isifunda esibucayi kufanele sihanjiswe kuqala, futhi indlela yokuhlanganisa phakathi kwamasekhethi kufanele iqedwe. Ngokuyinhloko, cabanga ngewashi, ukusetha kabusha kanye nokuphazamisa imigqa, ungahambisani nale migqa nezintambo eziphakeme zamanje, kungenjalo zonakaliswe kalula ngamasiginali wokuhlanganisa kagesi, okubangela ukusetha kabusha noma ukuphazamisa okungalindelekile. The overall layout should follow the following principles:

1. Ukuhlelwa kokuhlukaniswa okusebenzayo, isekethe ye-analog nesekethe yedijithali ku-PCB kufanele kube nokuhlelwa kwendawo okuhlukile.

2. Ngokwenqubo yesiginali yesekethe ukuhlela amayunithi wesekethe asebenzayo, ukuze ukugeleza kwesiginali kugcine isiqondiso esifanayo.

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. Izingxenye eziphazamiseka kalula akufanele zisondelane kakhulu, izingxenye zokufakwayo neziphumayo kufanele zibe kude.

How to design the signal of integrity PCB

Ukwakhiwa kwentambo ye-PCB

Yonke imigqa yesiginali kufanele ihlukaniswe ngaphambi kwentambo ye-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. Izintambo zesiginali ezizendlalelo ezihlukene kufanele zihanjiswe ziqonde kwenye ukuze kuncishiswe i-crosstalk. Ukuhlelwa kwemigqa yesignali kuhle kakhulu ngokulandela isiqondiso sokugeleza kwesignali. Ulayini wesignali ophumayo wesekethe akufanele ubuyiselwe emuva endaweni yomugqa wesiginali yokufaka. High-speed signal lines should be kept as short as possible to avoid interfering with other signal lines. Kwiphaneli elikabili, uma kunesidingo, intambo yomhlabathi ehlukanisiwe ingangezwa ezinhlangothini zombili zomugqa wesiginali esinejubane eliphezulu. Yonke imigqa yewashi enesivinini esiphezulu ebhodini le-multilayer kufanele ivikelwe ngokuya ngobude bemigqa yewashi.

Izimiso ezijwayelekile zokufaka izintambo yilezi:

1. Ngokungase ukwazi ukukhetha idizayini yezintambo eziminyana kancane, kanye nezintambo zesignali ngangokunokwenzeka ukushuba okungaguquki, okuhambisana nokumadanisa kwe-impedance. Okwesekethe ye-rf, ukwakheka okungenangqondo kokuqondiswa kolayini wesiginali, ububanzi nokuhlukaniswa kwemigqa kungadala ukuphazamiseka kokuwela phakathi kwemigqa yokudlulisela isignali.

2. ngangokunokwenzeka ukugwema izintambo zokufaka nezokukhipha eziseduze nezintambo ezihambelana nebanga elide. Ukunciphisa i-crosstalk yemigqa yesignali ehambisanayo, isikhala phakathi kwemigqa yesignali singandiswa, noma amabhande okuhlukanisa angafakwa phakathi kwemigqa yesignali.

3. Ububanzi bolayini ku-PCB buzoba ngokufana futhi akukho ukuguquka kobubanzi bomugqa okuzokwenzeka. I-PCB yokugoba izintambo akufanele isebenzise ikona elingu-90 degrees, kufanele isebenzise i-arc noma i-Angle engu-135 degrees, ngangokunokwenzeka ukuze kugcinwe ukuqhubeka komugqa wokuvimba.

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. Ngangokunokwenzeka ukunciphisa ubude bocingo, ukwandisa ububanzi bocingo, kuyasiza ekunciphiseni i-impedance yocingo.

6. Ngamasignali okulawula ukushintsha, inombolo yezintambo ze-SIGNAL PCB ezishintsha isimo ngesikhathi esifanayo kufanele yehliswe ngokusemandleni akho.