Otu esi ezere mmetụta nnyefe na PCB dị elu design

1. Ụzọ iji gbochie nnyonye anya electromagnetic

Ezi ngwọta maka nsogbu iguzosi ike n’ezi ihe mgbaàmà ga -eme ka ndakọrịta elektrik (EMC) nke bọọdụ PCB dị mma. Otu n’ime ihe kachasị mkpa bụ ijide n’aka na bọọdụ PCB nwere ezigbo ntọala. Ogwe mgbaama nwere akwa ala bụ ụzọ dị oke mma maka imepụta mgbagwoju anya. Tụkwasị na nke ahụ, ibelata njupụta nrịba ama nke akwa mpụta nke bọọdụ sekit bụkwa ụzọ dị mma iji belata radieshon electromagnetic. Enwere ike nweta usoro a site na iji teknụzụ “elu mpaghara” imebe PCB. A na-enweta akwa oyi akwa site na ịgbakwunye ngwakọta mkpuchi mkpuchi dị mkpa na micropores ejiri banye n’ime akwa ndị a na PCB usoro. Enwere ike lie iguzogide na ikike n’okpuru elu, yana njupụta ahịrị dị n’otu mpaghara fọrọ nke nta ka ọ bụrụ okpukpu abụọ, si otú a belata olu nke PCB. Mbelata mpaghara PCB nwere nnukwu mmetụta na topology nke ntụgharị, nke pụtara na loop dị ugbu a belatara, ogologo nke usoro alaka ụlọ ọrụ na -ebelata, radieshon electromagnetic dịkwa nha na mpaghara nke loop ugbu a; At the same time, the small size characteristics mean that high-density pin packages can be used, which in turn reduces the length of the wire, thus reducing the current loop and improving emc characteristics.

2. Strictly control the cable lengths of key network cables

If the design has a high speed jump edge, the transmission line effect on the PCB must be considered. Ọnụego elekere dị elu ngwa ngwa agbakwunyere sekit a na -ejikarị eme ihe taa nwere nsogbu. Enwere ụfọdụ ụkpụrụ dị mkpa iji dozie nsogbu a: ọ bụrụ na ejiri okirikiri CMOS ma ọ bụ TTL mee ihe, ugboro ole ọ na -arụ ọrụ erughị 10MHz, ogologo eriri ya ekwesịghịkwa karịa sentimita 7. If the operating frequency is 50MHz, the cable length should not be greater than 1.5 inches. Wiring length should be 1 inch if operating frequency reaches or exceeds 75MHz. Ogologo ogologo wiring maka ibe GaAs kwesịrị ịbụ 0.3 sentimita. Ọ bụrụ na nke a gafere, enwere nsogbu ahịrị nnyefe.

3. Kwadebe nke ọma na topology nke cabling

Another way to solve the transmission line effect is to choose the correct routing path and terminal topology. Topology cabling na -ezo aka n’usoro cabling na nhazi nke eriri netwọkụ. Mgbe ejiri ngwa mgbagha dị elu, ngalaba ogwe mgbaama ga-agbagọ mgbama nke nwere akụkụ na-agbanwe ngwa ngwa ọ gwụla ma edobere ogologo alaka ahụ mkpụmkpụ. Na mkpokọta, ụzọ PCB na -anabata topologies abụọ, ya bụ ụzọ ụzọ Daisy Chain na nkesa Star.

Maka eriri wiwi daisy, wiring na-amalite na njedebe ọkwọ ụgbọ ala wee rute njedebe nnata ọ bụla. Ọ bụrụ na ejiri resistor usoro iji gbanwee njirimara mgbaama, ọnọdụ resistor usoro kwesịrị ịdị nso na njedebe ịnya ụgbọ ala. Njikọ eriri Daisy kacha mma n’ịchịkwa nnyonye anya dị elu nke eriri. Agbanyeghị, ụdị wiring a nwere ọnụego nnyefe kacha ala ma ọ dịghị mfe ịgafe 100%. N’ime atụmatụ ahụ n’ezie, anyị chọrọ ime ka alaka ụlọ ọrụ ahụ dị na eriri eriri Daisy dị nkenke ka o kwere mee, na uru ịdị ogologo ya kwesịrị ịdị: Stub Delay < = Trt * 0.1.

Dịka ọmụmaatụ, ngalaba na-ejedebe na sekit TTL dị elu kwesịrị ịdị ihe na-erughị sentimita 1.5 n’ogologo. Topology a na -ewe obere oghere wiring ma nwee ike kwụsị ya site na otu nguzogide kwekọrọ. Agbanyeghị, usoro wiring a na -eme ka mgbaama na -anata na ihe nnata mgbaama dị iche iche abụghị otu.

The star topology can effectively avoid the problem of clock signal synchronization, but it is very difficult to finish the wiring manually on the PCB with high density. Iji eriri akpaka bụ ụzọ kachasị mma iji mezue eriri kpakpando. A terminal resistor is required on each branch. The value of the terminal resistance should match the characteristic impedance of the wire. Enwere ike iji aka gị mee nke a ma ọ bụ site na ngwaọrụ CAD gbakọọ ụkpụrụ impedance njirimara yana ọnụ ahịa nguzogide kwekọrọ.

While simple terminal resistors are used in the two examples above, a more complex matching terminal is optional in practice. Nhọrọ nke mbụ bụ ọdụ egwuregwu RC. Ntanetị RC dakọtara nwere ike belata oriri ike, mana enwere ike iji ya naanị mgbe ọrụ mgbaama kwụsiri ike. Usoro a kacha dabara maka nhazi akara akara elekere. Ọdịmma ya bụ na ikike dị na ọdụ RC dakọtara nwere ike imetụta ọdịdị na mgbapụta mgbaama.

The series resistor matching terminal incurs no additional power consumption, but slows down signal transmission. This approach is used in bus-driven circuits where time delays are not significant. Usoro resistor dabara na ọnụ nwekwara uru nke mbenata ọnụ ọgụgụ ngwaọrụ ejiri na bọọdụ yana njupụta nke njikọ.

The final method is to separate the matching terminal, in which the matching element needs to be placed near the receiving end. Uru ya bụ na ọ gaghị akwada mgbama ahụ, ọ ga -adịkwa mma iji zere mkpọtụ. A na -ejikarị maka akara ntinye TTL (ACT, HCT, FAST).

In addition, the package type and installation type of the terminal matching resistor must be considered. SMD surface mount resistors generally have lower inductance than through-hole components, so SMD package components are preferred. There are also two installation modes for ordinary straight plug resistors: vertical and horizontal.

N’ọnọdụ ịgbatị kwụ ọtọ, nguzogide nwere ntụtụ na -agbago nkenke, nke na -ebelata nguzogide ọkụ n’etiti nguzogide na bọọdụ sekit ma na -eme ka ikpo ọkụ na -eguzogide dị mfe ịbanye n’ime ikuku. Mana nrụnye kwụ ọtọ ogologo ga -abawanye inductance nke resistor. Horizontal installation has lower inductance due to lower installation. However, the overheated resistance will drift, and in the worst case, the resistance will become open, resulting in PCB wiring termination matching failure, becoming a potential failure factor.

4. Teknụzụ ndị ọzọ metụtara

Iji belata oke ọkụ na -agafe agafe na ọkọnọ ike IC, ekwesịrị ịgbakwunye capacitor decoup na mgbawa IC. Nke a na -ewepụ mmetụta nke burrs na ọkọnọ ọkụ ma na -ebelata radieshon site na loop ike na bọọdụ ebipụtara.

Mmetụta na -ebelata ire ụtọ na -akacha mma mgbe ejikọtara decoupling capacitor ozugbo na ụkwụ ike ọkọnọ nke sekit agbakwunyere karịa na oyi akwa ọkọnọ. Nke a bụ ya mere ụfọdụ ngwaọrụ ji enwe ihe ndọda capacitors na sọks ha, ebe ndị ọzọ na -achọ ka anya dị n’etiti ndọda capacitor na ngwaọrụ ahụ pere mpe.

Ekwesịrị ịjikọ ngwa ngwa ọ bụla dị elu na ike oriri dị ka o kwere mee iji belata nfefe ọkụ eletrik.

Enweghị ike oyi, ogologo ahịrị ike na -etolite oghere n’etiti mgbama na loop, na -eje ozi dị ka isi iyi radieshon na sekit inductive.

Cabling na -akpụ akaghị nke na -anaghị agafe n’otu eriri netwọkụ ma ọ bụ eriri ndị ọzọ ka a na -akpọ loop mepere emepe. Ọ bụrụ na loop na -agafe n’otu eriri netwọkụ, ụzọ ndị ọzọ na -eme mkpọchi mechiri emechi. N’ọnọdụ abụọ a, mmetụta antenna (antenna ahịrị na antenna mgbanaka) nwere ike ime.