PCBgogo

Electronic Project Engineer's Best Partner!
D****orV
7 tips for high-speed PCB-routing design
6570 23 Sep 03.2022, 10:08:27


1. Power Supply and Circuit Routing



Most of the time digital circuits need discontinuous current, which would generate inrush current. 


And there must exist parasitic inductance, parasitic resistance, and parasitic capacitor in the high-speed circuit, so eventually, the high-frequency noise would be coupled into other circuits. Because parasitic inductance will decline the maximum inrush current capability that can be withstood, and then cause some parts pressure to drop, and the circuit may be disabled.


Therefore, it is particularly important to add bypass capacitors in front of digital devices. The larger the capacitor is, the more energy it transmits is limited by the transmission rate, so a large capacitor and a small capacitor are generally combined to satisfy the full frequency range.




Avoid hot spots: Signal vias will create voids on the power plane and bottom layer. Therefore, the unreasonable placement of vias is likely to increase the current density in some areas of the power or ground plane. And these places where the current density increases are called hot spots.


So, we should try our best to avoid this situation when setting the vias, so as to avoid the plane being split, which will eventually lead to EMC problems.

Usually the best way to avoid hot spots is to place vias in a mesh pattern, so that the current density is uniform, and the planes are not isolated, the return path is not too long, and there is no EMC problem.




2. Ways to Insert a Bend in Traces



When laying high-speed signal lines, the signal lines should try to avoid bending. If you have to bend the trace, don't run it at an acute or right angle, but use an obtuse trace.



When laying out high-speed signal lines, we often use serpentine lines to achieve equal lengths, and the same serpentine lines are actually a kind of bending. The line width, spacing, and bending method should be selected reasonably, and the spacing should meet the 4W/1.5W rule.




3. Proximity Signal



If the distance between high-speed signal lines is too close, it is easy to generate crosstalk. Sometimes, due to circuits routing, board frame size and other reasons, the distance between the high-speed signal lines exceeds our minimum required distance, so we can only try to increase the distance between the high-speed signal lines near the bottleneck. distance.


In fact, if the space is enough, try to increase the distance between the two high-speed signal lines.




4. Stub Line



A long stub line is equivalent to an antenna, and improper handling can cause serious EMC problems.


At the same time, the stub line will also cause reflections, reducing the integrity of the signal. Usually, when a pull-up or pull-down resistor is added to the high-speed signal line, it is most likely to generate a stub line, and generally, the stub line can be routed in a daisy chain.


According to experience, if the length of the stub line is greater than 1/10 wavelength, it can be used as an antenna, which will become a problem at this time.




5. Impedance Discontinuities



The impedance value of a trace generally depends on its width and the distance between the trace and the reference plane. The wider the trace, the lower its impedance. In some interface terminals, which are also the pads of the device, the same principle applies.


When the pad of an interface terminal is connected to a high-speed signal line, if the pad is very large at this time, and the high-speed signal line is very narrow, the impedance of the large pad is small, and the narrow trace must have a large impedance. In this case, there will be impedance discontinuities, and impedance discontinuities will produce signal reflections.


Therefore, in order to solve this problem in general, a forbidden copper sheet is placed under the interface terminal or the large pad of the device, and at the same time, the reference plane of the pad is placed on another layer, thereby increasing the impedance and making the impedance continuous.



Vias are another source of impedance discontinuities. To minimize this effect, the unwanted copper layers connected to the inner layers and vias should be removed.


In fact, such an operation can be used to eliminate unnecessary copper sheets through CAD tools during design or contact the PCB processing manufacturer to ensure the continuity of impedance.




6. Differential Signaling



For high-speed differential signal lines, we must ensure equal width and equal spacing to achieve a specific differential impedance value. Therefore, try to ensure symmetry when laying out differential signal lines.



It is forbidden to arrange vias or components in the differential pair. If vias or components are placed in the differential pair, EMC problems will occur and impedance discontinuities will also be caused.



Sometimes, some high-speed differential signal lines require series coupling capacitors. The coupling capacitor also needs to be symmetrically arranged. At the same time, the package of the coupling capacitor should not be too large. It is recommended to use 0402 and 0603. It is also acceptable to use capacitors above 0805 or side-by-side capacitors.



Typically, vias create huge impedance discontinuities, so for high-speed differential signal pairs, minimize vias, and use vias symmetrically if they are to be used.




7. Isometric Circuit



In some high-speed signal interfaces, such as a bus, it is generally necessary to consider the arrival time and skew error between the signal lines. For example, the arrival time of all data signal lines in a group of high-speed parallel buses must be guaranteed to be within a certain time delay error, so as to ensure the consistency of its setup time and hold time. To meet this need, we must consider isometrics.


The high-speed differential signal line must ensure a strict time delay between the two signal lines, otherwise the communication is likely to fail. Therefore, in order to meet this requirement, the serpentine line can be used to achieve the same length, thereby meeting the time delay requirement.



Serpentines should generally be placed at the source of the elongation, not the distal end. Only at the source can the signals at the positive and negative ends of the differential line be transmitted synchronously most of the time.



The bend of the trace is one of the sources of loss of length. For the bend of the trace, its equal length should be close to the bend (<=15mm)



If two traces are bent and the distance between them is less than 15mm, the loss of length between the two will compensate each other, so there is no need to do equal-length processing at this time.



For different parts of the high-speed differential signal lines, they should be independent and equal in length. Vias, series coupling capacitors and interface terminals will be divided into two parts for high-speed differential signal lines, so special attention should be paid at this time.


Must be of equal length. Because a lot of EDA software only pays attention to whether the entire trace is not long during DRC.



For interfaces such as LVDS display devices, there will be several pairs of differential pairs at the same time, and the timing requirements between the differential pairs are generally very strict, and the time delay requirements are particularly small. Therefore, for such differential signal pairs, we generally require them to be in the same plane. to compensate. Because the signal transmission speed of different layers is different.



When some EDA software calculates the length of the trace, the trace inside the pad will also be calculated within the length. If the length compensation is performed at this time, the final actual result will be lost. So pay special attention at this time, when using some EDA software.



Whenever possible, choose symmetrical routing to avoid the need to end up serpentine routing for equal lengths.



If space permits, try to compensate by adding a small loopback at the source of the short differential line instead of serpentine.



  • Comments(23)
Upload a photo:You can only upload 1 files in total. Each file cannot exceed 2MB.Supports JPG, JPEG, GIF, PNG, BMP
Browse
Submit
header
m****esa

Dec 09.2024, 12:04:29

<a href="https://www.pursemalla.cn/dior-bags">Replica dior bags</a>

Reply

Submit
header
m****esa

Dec 09.2024, 12:03:14

[url="https://www.pursemalla.cn/dior-bags"]Replica dior bags[/url]

Reply

Submit
header
m****esa

Dec 09.2024, 12:02:40

<a href="https://www.pursemalla.cn/dior-bags">Replica dior bags</a>

Reply

Submit
header
O****own

Dec 09.2024, 04:25:39

Thank you for this thoughtful and well-organized post! I fully agree with your perspective, and your advice is practical and easy to apply. I’ll be sure to remember this the next time I’m betting <a href="https://kenya-melbet.com/download-the-melbet-app-in-kenya-start-mobile-betting-now/">Melbet app in Kenya</a> on soccer, tennis, or even basketball. Keep up the great work—your posts are a pleasure to read!

Reply

Submit
header
**

Dec 03.2024, 12:23:11

The discussion surrounding high-speed PCB routing is crucial in today's tech-driven world. The tips provided can significantly enhance performance. Companies such as jdbpcb and PCB solution provider - AnyPCBA offer excellent services that align with these best practices, ensuring optimal outcomes for various projects.

Reply

Submit
header
**

Nov 13.2024, 15:51:13

You possess lifted an essential offspring..Blesss for using..I would want to study better latest transactions from this blog..preserve posting.. patek aquanaut replica

Reply

Submit
header
J****tin

Oct 15.2024, 09:30:56

Designing high-speed PCBs requires precision and attention to detail, much like solving a puzzle in Wordle Unlimited. Just as in the game, where every letter placement can make or break your success, PCB routing depends on careful planning and execution to ensure signal integrity and performance.
<a href="https://wordleunlimitedplay.com/">wordle unlimited</a>
[url=https://wordleunlimitedplay.com/]wordle unlimited[/url]
[wordle unlimited](https://wordleunlimitedplay.com/)


Reply

Submit
header
**

Oct 10.2024, 15:18:01

I use basically superior fabrics : you will discover these products by: Tax preparation services

Reply

Submit
header
**

Oct 02.2024, 15:34:14

I've proper selected to build a blog, which I hold been deficient to do for a during. Acknowledges for this inform, it's really serviceable! Frozen Pork Half Carcass

Reply

Submit
header
**

Oct 01.2024, 15:37:26

It is rather very good, nevertheless glance at the data with this handle. replica patek philippe

Reply

Submit
header
**

Sep 24.2024, 00:31:53

The most interesting text on this interesting topic that can be found on the net ...  buy reel views

Reply

Submit
header
B****iel

Sep 09.2024, 17:16:18

Krunker io user interface is intuitive and easy to navigate. I appreciate the variety of settings and customization options available. It’s also awesome how the game supports mods and custom content. Makes each session feel new and engaging!

Reply

Submit
header
J****ney

Jul 25.2024, 10:08:04

It's worth noting that while parasitic inductance can limit inrush current capability, proper design techniques, such as using snubber circuits or careful layout practices, can help mitigate these issues. Overall, the post provides a solid overview of the complexities in managing current and noise in digital Papa's Games circuits.

Reply

Submit
header
**

Jun 29.2024, 14:19:27

Designing high-speed PCB-routing demands careful consideration. Tips include: 1. Plan signal paths for optimal length. 2. Minimize gout in foot signal reflections with controlled impedance. 3. Use ground planes for noise reduction. 4. Maintain signal integrity with proper layer stackup. 5. Avoid sharp bends and crossings. 6. Separate high-speed and low-speed signals. 7. Verify designs with simulation tools for reliability.

Reply

Submit
header
**

Jun 13.2024, 23:00:38

Um brinde a todos. A leitura do artigo sobre as rivalidades futebolísticas na América do Sul na Mostbet Portugal foi um verdadeiro prazer para mim. O autor descreve com mestria os momentos-chave e os contextos históricos dos grandes dérbis, sublinhando a paix?o e as emo??es que evocam. Foi interessante conhecer o impacto destas rivalidades na sociedade e na cultura. O artigo está escrito de forma viva e cativante, n?o só é informativo, mas também proporciona uma vis?o mais profunda do espírito do futebol sul-americano. Recomendo-o a todos os entusiastas do futebol e f?s de histórias emocionantes!

Reply

Submit
header
A****lli

Apr 13.2024, 12:46:05

If you're wondering if Speedypaper is reliable, I'd say yes with confidence [URL=https://www.linkedin.com/pulse/honest-speedypapercom-review-mindy-small-hr8vc/]read in this speedypaper review[/URL]. Their prompt delivery, quality content, and attentive customer service make them a top choice. I've used their services multiple times, and each time they've exceeded my expectations. Definitely recommend for anyone needing academic assistance!

Reply

Submit
header
L****ncy

Apr 09.2024, 16:31:00

To cover all frequencies, it is common practice to connect large and small capacitors. This is because the amount of energy that a capacitor can broadcast is proportional to its size and the transmission rate.

basketball stars

Reply

Submit
header
L****ncy

Apr 09.2024, 16:30:47

To cover all frequencies, it is common practice to connect large and small capacitors. This is because the amount of energy that a capacitor can broadcast is proportional to its size and the transmission rate.

<a href="https://basketball-starsgame.io/">basketball stars</a>

Reply

Submit
header
S****els

Mar 19.2024, 07:15:50

Hi everyone, I recommend you read a cool review of Golden Lady Casino for players in Australian. They offer extensive resources and tools to help players control their gambling habits, including self-exclusion options, deposit limits and links to support organisations for those who need help. In addition, strict age verification measures ensure that only players who are of legal gambling age can access the platform. I highly recommend this review, there is a lot more interesting information in it.

Reply

Submit
header
**

Mar 13.2024, 17:03:24

I recently discovered Playnow Casino , and I'm thoroughly impressed with what they have to offer. The platform boasts a diverse selection of games from top software providers, ensuring endless entertainment for players of all preferences. The bonuses and promotions are among the best I've seen, with plenty of opportunities to boost your bankroll. I also appreciate the user-friendly interface and seamless gameplay experience. Whether you're a seasoned player or new to online gaming, Playnow Casino is definitely worth checking out.

Reply

Submit
header
M****ke

Feb 29.2024, 04:09:04

If you are a new player from Cameroon and want to register at MelBet correctly, I recommend that you visit https://melbetcameroun.app/inscription/. There you will find detailed instructions on how to register an account, which will help you avoid mistakes and become a member as quickly as possible. It is important to follow every step of the registration process, including entering the correct data and confirming your contact information. MelBet provides a variety of betting and gaming opportunities, so registering correctly will ensure that you have access to all the benefits of the platform.

Reply

Submit
header
u****ble

Nov 28.2023, 09:36:17

A large and a small capacitor are typically coupled to cover the entire frequency range since the amount of energy that a capacitor can broadcast depends on its size and the transmission rate.

Reply

Submit
header
V****olt

Oct 20.2023, 16:02:06

Woww. Amazing  geometry dash online tips. I'll share it to my friends.

Reply

Submit
Share the Project