Pẹlu awọn ilosoke ti ese Circuit o wu yipada iyara ati PCB ọkọ 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. Iyara ifihan agbara giga lori PCB kan, gbigbe ti ko tọ ti awọn paati ipari, tabi wiwọn ti ko tọ ti awọn ifihan agbara iyara le fa awọn iṣoro iduroṣinṣin ifihan, eyiti o le fa ki eto naa jade data ti ko tọ, Circuit lati ṣiṣẹ aiṣedeede tabi ko ṣiṣẹ rara. Bii o ṣe le mu iduroṣinṣin ifihan sinu ero ni kikun ati mu awọn iwọn iṣakoso to munadoko ninu apẹrẹ PCB ti di koko ti o gbona ni ile -iṣẹ apẹrẹ PCB.

Signal integrity Problem Good signal integrity means that the signal can respond with the correct timing and voltage level values when required. Lọna miiran, nigbati ifihan naa ko dahun daradara, iṣoro iduroṣinṣin ifihan kan wa. Awọn iṣoro iduroṣinṣin ami ifihan le ja si tabi taara taara si ipalọlọ ifihan, awọn aṣiṣe akoko, data ti ko tọ, adirẹsi ati awọn laini iṣakoso, ati aibikita eto, tabi paapaa jamba eto. Ninu ilana ti adaṣe apẹrẹ PCB, eniyan ti kojọpọ pupọ ti awọn ofin apẹrẹ PCB. Ni apẹrẹ PCB, iduroṣinṣin ifihan ti PCB le ṣaṣeyọri dara julọ nipa tọka tọka si awọn ofin apẹrẹ wọnyi.

Nigbati o ba n ṣe apẹrẹ PCB, a gbọdọ kọkọ ni oye alaye apẹrẹ ti gbogbo igbimọ Circuit, eyiti o pẹlu pẹlu:

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. Iru laini ifihan, iyara ati itọsọna gbigbe, awọn ibeere iṣakoso ikọja ti laini ifihan, itọsọna iyara ọkọ akero ati ipo awakọ, awọn ami bọtini ati awọn ọna aabo;

4. Iru ipese agbara, iru ilẹ, awọn ibeere ifarada ariwo fun ipese agbara ati ilẹ, eto ati ipin ti ipese agbara ati ọkọ ofurufu ilẹ;

5. Awọn oriṣi ati awọn oṣuwọn ti awọn laini aago, orisun ati itọsọna ti awọn laini aago, awọn ibeere idaduro aago, awọn ibeere laini to gunjulo.

Apẹrẹ fẹlẹfẹlẹ PCB

Lẹhin agbọye alaye ipilẹ ti igbimọ Circuit, o jẹ dandan lati ṣe iwọn awọn ibeere apẹrẹ ti idiyele igbimọ Circuit ati iduroṣinṣin ifihan, ati yan nọmba ti o peye ti awọn fẹlẹfẹlẹ wiwa. 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. Ofurufu itọkasi yoo dara julọ jẹ ọkọ ofurufu ilẹ. Ipese agbara mejeeji ati ọkọ ofurufu ilẹ le ṣee lo bi ọkọ ofurufu itọkasi, ati pe awọn mejeeji ni iṣẹ aabo kan. Bibẹẹkọ, ipa aabo ti ọkọ ofurufu ipese agbara kere pupọ ju ti ọkọ ofurufu ilẹ nitori idiwọ ikọlu ti o ga julọ ati iyatọ nla ti o pọju laarin ọkọ ofurufu ipese agbara ati ipele itọkasi ilẹ.

2. Digital circuit and analog circuit are layered. Nibiti awọn idiyele idiyele gba laaye, o dara julọ lati ṣeto awọn oni -nọmba ati awọn iyika analog lori awọn fẹlẹfẹlẹ lọtọ. If must want to arrange in same wiring layer, can use ditch, add earthing line, the method such as dividing line to remedy. Analog ati agbara oni -nọmba ati ilẹ gbọdọ wa niya, ko dapọ.

3. Ipa ọna ifihan bọtini ti awọn fẹlẹfẹlẹ ti o wa nitosi ko kọja agbegbe ipin. Awọn ifihan agbara yoo ṣe lupu ifihan nla kan kọja agbegbe naa ati ṣe ina itankalẹ to lagbara. 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. O yẹ ki ọkọ ofurufu ilẹ ti o pe ni pipe wa ni isalẹ apa paati. Iduroṣinṣin ti ọkọ ofurufu ilẹ gbọdọ wa ni itọju bi o ti ṣee ṣe fun awo pupọ. Ko si awọn laini ifihan ti o gba laaye deede lati ṣiṣẹ ninu ọkọ ofurufu ilẹ.

5, igbohunsafẹfẹ giga, iyara to gaju, aago ati awọn laini ifihan agbara bọtini miiran yẹ ki o ni ọkọ ofurufu ilẹ ti o wa nitosi. 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

Bọtini ti apẹrẹ iduroṣinṣin ifihan ti igbimọ ti a tẹjade jẹ ipilẹ ati wiwu, eyiti o ni ibatan taara si iṣẹ ti PCB. Prior to layout, the PCB size must be determined to meet the function at the lowest possible cost. Ti PCB ba tobi pupọ ti o pin kaakiri, laini gbigbe le pẹ pupọ, ti o mu ki ikọlu pọ si, idinku ariwo dinku, ati idiyele ti o pọ si. Ti o ba jẹ pe awọn paati ti wa ni papọ, ifasita igbona ko dara, ati idapọmọra idapọmọra le waye ni wiwirin ti o wa nitosi. Nitorinaa, akọkọ gbọdọ da lori awọn sipo iṣẹ ti Circuit, lakoko ti o n gbero ibaramu itanna, itusilẹ ooru ati awọn ifosiwewe wiwo.

Nigbati o ba gbe PCB jade pẹlu oni nọmba aladapọ ati awọn ami afọwọṣe, maṣe dapọ awọn ami oni -nọmba ati afọwọṣe. Ti awọn ami afọwọṣe ati oni-nọmba gbọdọ jẹ adalu, rii daju lati laini ni inaro lati dinku ipa ti isọdọkan. Circuit oni-nọmba, Circuit analog, ati Circuit ti n ṣe ariwo lori igbimọ Circuit yẹ ki o ya sọtọ, ati Circuit ti o ni itara yẹ ki o kọkọ kọkọ lọ, ati ọna asopọ laarin awọn iyika yẹ ki o yọkuro. Ni pataki, gbero aago, tunto ati awọn laini idiwọ, ma ṣe afiwe awọn laini wọnyi pẹlu awọn laini iyipada ti o ga lọwọlọwọ, bibẹẹkọ ni rọọrun bajẹ nipasẹ awọn ami idapọ itanna, nfa idawọle airotẹlẹ tabi da gbigbi. The overall layout should follow the following principles:

1. Ifilelẹ ipin iṣẹ, Circuit analog ati Circuit oni nọmba lori PCB yẹ ki o ni ipilẹ aye oriṣiriṣi.

2. Ni ibamu si ilana ifihan Circuit lati ṣeto awọn sipo iṣẹ ṣiṣe, ki ṣiṣan ifihan lati ṣetọju itọsọna kanna.

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. Awọn paati ti o ni rọọrun ko yẹ ki o sunmọ ara wọn, titẹ sii ati awọn paati iṣelọpọ yẹ ki o jinna.

How to design the signal of integrity PCB

Apẹrẹ wiwa PCB

Gbogbo awọn laini ifihan yẹ ki o wa ni tito lẹtọ ṣaaju wiwa 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. Awọn kebulu ifihan agbara lori awọn fẹlẹfẹlẹ oriṣiriṣi yẹ ki o wa ni inaro si ara wọn lati dinku crosstalk. Eto ti awọn laini ifihan jẹ idayatọ ti o dara julọ ni ibamu si itọsọna ṣiṣan ti ifihan. Laini ifihan agbara iṣelọpọ ti Circuit ko yẹ ki o pada sẹhin si agbegbe laini ifihan titẹ sii. High-speed signal lines should be kept as short as possible to avoid interfering with other signal lines. Lori nronu ilọpo meji, ti o ba jẹ dandan, okun waya ilẹ ipinya le ṣafikun ni ẹgbẹ mejeeji ti laini ifihan agbara giga. Gbogbo awọn laini aago iyara-giga lori igbimọ multilayer yẹ ki o daabobo ni ibamu si gigun awọn laini aago.

Awọn ipilẹ gbogbogbo fun sisẹ ni:

1. Bi o ti ṣee ṣe lati yan apẹrẹ wiwọn iwuwo kekere, ati wiwọn ifihan agbara bi o ti ṣee ṣe sisanra ni ibamu, ti o ṣe deede si ibaamu ikọlu. Fun Circuit rf, apẹrẹ aironu ti itọsọna laini ifihan, iwọn ati aye laini le fa kikọluja larin awọn laini gbigbe ifihan.

2. Bi o ti ṣee ṣe lati yago fun igbewọle ti o wa nitosi ati awọn okun onirin ati wiwọ gigun ti o jọra gigun. Lati dinku crosstalk ti awọn laini ifihan afiwera, aye laarin awọn laini ifihan le pọ si, tabi awọn beliti ipinya le fi sii laarin awọn laini ifihan.

3. Iwọn ila lori PCB yoo jẹ iṣọkan ati pe ko si iyipada iwọn laini yoo waye. Bọtini wiwakọ PCB ko yẹ ki o lo igun iwọn 90, o yẹ ki o lo aaki tabi igun 135 iwọn, bi o ti ṣee ṣe lati ṣetọju ilosiwaju ti ikọja 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. Bi o ti ṣee ṣe lati dinku gigun ti okun waya, mu iwọn okun pọ si, jẹ idari lati dinku ikọlu okun waya naa.

6. Fun awọn ifihan iṣakoso iṣakoso yipada, nọmba ti wiwọn PCB SIGNAL ti o yi ipo pada ni akoko kanna yẹ ki o dinku bi o ti ṣee ṣe.