Tthe EMC ڊيزائن ۾ پي سي بي، پھرين تشويش آھي پرت جي جوڙجڪ بورڊ جي تہن مان powerھيل آھن پاور سپلائي ، زميني پرت ۽ سگنل ليئر. In EMC design of products, besides the selection of components and circuit design, good PCB design is also a very important factor.

The key to the EMC design of PCB is to minimize the backflow area and make the backflow path flow in the direction we designed. The layer design is the basis of PCB, how to do a good job of PCB layer design to make THE EMC effect of PCB optimal?

پي سي بي ليئر جي ڊيزائن جا خيال

The core of PCB laminated EMC planning and design is to reasonably plan signal backflow path to minimize the backflow area of signal from the board mirror layer, so as to eliminate or minimize magnetic flux.

Single board mirroring layer

آئيني پرت پي سي بي جي اندر سگنل پرت جي copperرسان ٽامي سان planeڪيل جهاز جي پرت (پاور سپلائي پرت ، گرائونڊنگ پرت) جي ھڪڙي پرت آھي. مکيه ڪم هن ريت آهن.

(1) پوئتي وهڻ جو شور گھٽايو: آئيني جو پرت سگنل پرت جي پوئتي وهڻ لاءِ گھٽ رڪاوٽ وارو رستو مهيا ڪري سگھي ٿو ، خاص طور تي جڏھن اتي بجليءَ جي ور system واري نظام ۾ ھڪڙو وڏو موجوده وهڪرو آھي ، آئيني پرت جو ڪردار و obviousيڪ واضح آھي.

(2) EMI گھٽائڻ: آئيني پرت جو وجود سگنل ۽ ريفلڪس ذريعي closedھيل بند لوپ جي ايراضي کي گھٽ ڪري ٿو ۽ EMI گھٽائي ٿو

(3) reduce crosstalk: help to control the crosstalk problem between signal lines in high-speed digital circuit, change the height of the signal line from the mirror layer, you can control the crosstalk between signal lines, the smaller the height, the smaller the crosstalk;

(4) Impedance control to prevent signal reflection.

Selection of mirror layer

(1) supplyئي پاور سپلائي ۽ زميني جهاز ريفرنس جهاز طور استعمال ڪري سگھجن ٿا ، ۽ اندروني وائرنگ تي ھڪ خاص بچاءُ وارو اثر آھي.

(2) Relatively speaking, the power plane has a high characteristic impedance, and there is a large potential difference with the reference level, and the high-frequency interference on the power plane is relatively large;

(3) From the perspective of shielding, the ground plane is generally grounded and used as the reference point of the reference level, and its shielding effect is far better than that of the power plane;

(4) جڏھن منتخب ڪريو حوالو جهاز ، زميني جهاز کي ترجيح ڏني وي ، ۽ پاور جهاز کي چونڊيو وي يو

Two, magnetic flux cancellation principle

According to Maxwell’s equations, all electrical and magnetic action between separate charged bodies or currents is transmitted through the intermediate region between them, whether it is a vacuum or solid matter. In a PCB, the flux is always propagated in the transmission line. If the rf backflow path is parallel to the corresponding signal path, the flux on the backflow path is in the opposite direction to that on the signal path, then they are superimposed on each other, and the effect of flux cancellation is obtained.

مقناطيسي وهڪري جي منسوخي جي نوعيت

The essence of flux cancellation is the control of signal backflow path, as shown in the following diagram:

The right hand rule explains the magnetic flux cancellation effect

How to use the right hand rule to explain the magnetic flux cancellation effect when the signal layer is adjacent to the stratum is explained as follows:

(1) When a current flows through the wire, a magnetic field will be generated around the wire, and the direction of the magnetic field is determined by the right hand rule.

(2) جڏھن twoه ھڪ toئي جي ويجھو ھوندا آھن ۽ تار سان متوازي ھوندا آھن ، جيئن ھي below ڏنل شڪل ۾ ڏيکاريو ويو آھي ، بجليءَ جي ڪنڊڪٽرز مان ھڪڙو drainاھر ڪڻ لاءِ ، otherيو ھڪڙو بجليءَ جو ڪنڊڪٽر وهڻ لاءِ ، جيڪڏھن برقي ڪرنٽ وهندو آھي. تار آهن ڪرنٽ ۽ ان جو موٽڻ آهي موجوده سگنل ، پوءِ currentه مخالف رخ موجوده جي برابر آهن ، تنهنڪري انهن جو مقناطيسي ميدان برابر آهي ، پر هدايت سامهون آهي ،تنھنڪري اھي ھڪ otherئي کي منسوخ ڪن ٿا.

Five, six board design examples

For six layers, plan 3 is preferred

تجزيه:

(1) جيئن ته سگنل ليئر ريفلو ريفرنس جهاز جي ويجھو آھي ، ۽ S1 ، S2 ۽ S3 زميني جهاز جي رسان آھن ، بھترين مقناطيسي وهڪرو منسوخ ڪرڻ جو اثر حاصل ٿيو آھي. تنهن ڪري ، S2 آهي ترجيحي روٽنگ پرت ، پ Sيان S3 ۽ S1.

(2) The power plane is adjacent to the GND plane, the distance between the planes is very small, and it has the best magnetic flux cancellation effect and low power plane impedance.

(3) The main power supply and its corresponding floor cloth are located at layer 4 and 5. When layer thickness is set, the spacing between S2-P should be increased and the spacing between P-G2 should be reduced (the spacing between layer G1-S2 should be correspondingly reduced), so as to reduce the impedance of the power plane and the influence of the power supply on S2.

For six layers, option 4

تجزيه:

Scheme 4 is more suitable than Scheme 3 for local, small number of signal requirements, which can provide an excellent wiring layer S2.

Worst EMC effect, plan 2

Analysis: In this structure, S1 and S2 are adjacent, S3 and S4 are adjacent, and S3 and S4 are not adjacent to the ground plane, so the magnetic flux cancellation effect is poor.

نتيجو

Specific principles of PCB layer design:

(1) There is a complete ground plane (shield) below the component surface and welding surface;

(2) ڪوشش ڪريو بچڻ جي س directي طرح adjن سگنل جي تہن جي acentرسان.

(3) س signalئي سگنل ليئر زميني جهاز جي ويجھو آھن جيترو پري تائين.

(4) وائرنگ ليئر تيز فریکوئنسي ، تيز رفتار ، گھڙيال ۽ keyين اھم اشارن ۾ adjرپور زميني جهاز ھجڻ گھرجي.