Pamoja na ongezeko la pato jumuishi mzunguko byte kasi na PCB bodi 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. Kasi ya juu ya ishara kwenye PCB, uwekaji usio sahihi wa vipengele vya mwisho, au wiring isiyo sahihi ya ishara za kasi inaweza kusababisha matatizo ya uadilifu wa ishara, ambayo inaweza kusababisha mfumo kutoa data isiyo sahihi, mzunguko kufanya kazi vibaya au kutofanya kazi kabisa. Jinsi ya kuzingatia uadilifu wa ishara na kuchukua hatua madhubuti za udhibiti katika muundo wa PCB imekuwa mada kuu katika tasnia ya muundo wa PCB.

Signal integrity Problem Good signal integrity means that the signal can respond with the correct timing and voltage level values when required. Kinyume chake, wakati ishara haijibu vizuri, kuna shida ya uadilifu wa ishara. Shida za uadilifu wa ishara zinaweza kusababisha au kusababisha moja kwa moja upotoshaji wa ishara, makosa ya muda, data isiyo sahihi, anwani na laini za kudhibiti, na utendakazi mbaya wa mfumo, au hata mfumo wa ajali. Katika mchakato wa mazoezi ya kubuni ya PCB, watu wamekusanya sheria nyingi za muundo wa PCB. Katika muundo wa PCB, uadilifu wa ishara ya PCB inaweza kupatikana vizuri kwa kurejelea kwa uangalifu sheria hizi za muundo.

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. Aina ya mstari wa ishara, kasi na mwelekeo wa maambukizi, mahitaji ya udhibiti wa impedance ya mstari wa ishara, mwelekeo wa kasi ya basi na hali ya kuendesha gari, ishara muhimu na hatua za ulinzi;

4. Aina ya usambazaji wa umeme, aina ya ardhi, mahitaji ya uvumilivu wa kelele kwa usambazaji wa umeme na ardhi, kuweka na kugawanya usambazaji wa umeme na ndege ya ardhini;

5. Aina na viwango vya laini za saa, chanzo na mwelekeo wa laini za saa, mahitaji ya kuchelewa kwa saa, mahitaji ya laini ndefu.

Ubunifu wa PCB

Baada ya kuelewa habari ya kimsingi ya bodi ya mzunguko, inahitajika kupima mahitaji ya muundo wa gharama ya bodi ya mzunguko na uaminifu wa ishara, na uchague idadi inayofaa ya safu za wiring. 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. Ndege ya kumbukumbu itakuwa ikiwezekana kuwa ndege ya chini. Usambazaji wa umeme na ndege ya ardhini inaweza kutumika kama ndege ya kumbukumbu, na zote zina kazi fulani ya kukinga. Walakini, athari ya kukinga ya ndege ya usambazaji wa umeme ni ya chini sana kuliko ile ya ndege ya chini kwa sababu ya hali ya juu ya tabia na tofauti kubwa kati ya ndege ya usambazaji wa umeme na kiwango cha chini cha kumbukumbu.

2. Digital circuit and analog circuit are layered. Ambapo gharama ya kubuni inaruhusu, ni bora kupanga mizunguko ya dijiti na analog kwenye tabaka tofauti. If must want to arrange in same wiring layer, can use ditch, add earthing line, the method such as dividing line to remedy. Analog na nguvu ya dijiti na ardhi lazima zitenganishwe, kamwe zisichanganywe.

3. Usambazaji wa ishara muhimu ya tabaka zilizo karibu haivuki eneo la kugawanyika. Ishara zitaunda kitanzi kikubwa cha mawimbi kote kanda na kutoa mionzi yenye nguvu. 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. Inapaswa kuwa na ndege kamili ya chini chini ya sehemu ya sehemu. Uadilifu wa ndege ya ardhini lazima ihifadhiwe iwezekanavyo kwa sahani ya multilayer. Hakuna mistari ya ishara kawaida inaruhusiwa kukimbia kwenye ndege ya ardhini.

5, masafa ya juu, kasi ya juu, saa na mistari mingine muhimu ya ishara inapaswa kuwa na ndege ya ardhini iliyo karibu. 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

Ufunguo wa muundo wa uadilifu wa ishara wa bodi iliyochapishwa ni mpangilio na wiring, ambayo inahusiana moja kwa moja na utendaji wa PCB. Prior to layout, the PCB size must be determined to meet the function at the lowest possible cost. Ikiwa PCB ni kubwa mno na inasambazwa, njia ya upokezaji inaweza kuwa ndefu sana, na kusababisha kuongezeka kwa kizuizi, kupunguza upinzani wa kelele, na kuongezeka kwa gharama. Ikiwa vifaa vimewekwa pamoja, utaftaji wa joto ni duni, na kuambatanisha crosstalk inaweza kutokea kwa wiring iliyo karibu. Kwa hivyo, mpangilio lazima uzingatie vitengo vya kazi vya mzunguko, wakati unazingatia utangamano wa umeme, utenguaji wa joto na sababu za kiolesura.

Unapoweka PCB yenye ishara mchanganyiko za dijiti na analogi, usichanganye mawimbi ya dijiti na analogi. Ikiwa ishara za analogi na dijiti lazima zichanganywe, hakikisha umeweka mstari wima ili kupunguza athari za uunganishaji mtambuka. Mzunguko wa dijiti, mzunguko wa analog, na mzunguko wa kuzalisha kelele kwenye ubao wa mzunguko unapaswa kutengwa, na mzunguko nyeti unapaswa kupitishwa kwanza, na njia ya kuunganisha kati ya nyaya inapaswa kuondolewa. Hasa, fikiria saa, kuweka upya na kukatiza mistari, usilinganishe mistari hii na mistari ya juu ya sasa ya kubadili, vinginevyo inaharibiwa kwa urahisi na ishara za kuunganisha za sumakuumeme, na kusababisha kuweka upya au kusumbua bila kutarajiwa. The overall layout should follow the following principles:

1. Mpangilio wa kuhesabu kazi, mzunguko wa Analog na mzunguko wa dijiti kwenye PCB inapaswa kuwa na mpangilio tofauti wa anga.

2. Kulingana na mchakato wa ishara ya mzunguko kupanga vitengo vya mzunguko wa kazi, ili mtiririko wa ishara kudumisha mwelekeo huo.

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. Vipengele vilivyovurugika kwa urahisi haipaswi kuwa karibu sana kwa kila mmoja, vifaa vya kuingiza na kutoa vinapaswa kuwa mbali.

How to design the signal of integrity PCB

Ubunifu wa wiring wa PCB

Mistari yote ya mawimbi inapaswa kuainishwa kabla ya nyaya za 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. Kebo za mawimbi kwenye tabaka tofauti zinapaswa kuelekezwa kwa wima ili kupunguza mazungumzo. Mpangilio wa mistari ya ishara ni bora kupangwa kulingana na mwelekeo wa mtiririko wa ishara. Mstari wa ishara ya pato la mzunguko haupaswi kurudishwa kwenye eneo la mstari wa ishara. High-speed signal lines should be kept as short as possible to avoid interfering with other signal lines. Kwenye jopo la mara mbili, ikiwa ni lazima, waya ya ardhi ya kutengwa inaweza kuongezwa kwa pande zote mbili za mstari wa ishara ya kasi. Mistari yote ya saa ya kasi kwenye ubao wa multilayer inapaswa kulindwa kulingana na urefu wa mistari ya saa.

Kanuni za jumla za wiring ni:

1. Kwa kadri inavyowezekana kuchagua muundo wa wiring wa chini, na wiring ishara kadiri inavyowezekana unene thabiti, inayofaa kwa impedance inayolingana. Kwa mzunguko wa rf, muundo usiofaa wa mwelekeo wa laini ya ishara, upana na nafasi ya mstari inaweza kusababisha usumbufu wa msalaba kati ya laini za usafirishaji wa ishara.

2. Kwa kadiri iwezekanavyo ili kuepuka waya za pembejeo na pato zilizo karibu na wiring za umbali mrefu za sambamba. Ili kupunguza msalaba wa mistari ya ishara inayofanana, nafasi kati ya laini za ishara inaweza kuongezeka, au mikanda ya kujitenga inaweza kuingizwa kati ya mistari ya ishara.

3. Upana wa mstari kwenye PCB utakuwa sare na hakuna mabadiliko ya upana wa mstari yatatokea. Pembe ya wiring ya PCB haipaswi kutumia kona ya digrii 90, inapaswa kutumia arc au Angle ya digrii 135, kwa kadri inavyowezekana kudumisha mwendelezo wa impedance ya laini.

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. Kwa kadri inavyowezekana kupunguza urefu wa waya, ongeza upana wa waya, ni nzuri kupunguza upeo wa waya.

6. Kwa ishara za udhibiti wa kubadili, idadi ya waya za SIGNAL PCB zinazobadilisha hali wakati huo huo zinapaswa kupunguzwa iwezekanavyo.