Questions tagged [layout]

Layout is the process of designing a PCB including placement of parts and routing of traces.

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229
votes
9answers
80k views

Decoupling caps, PCB layout

I guess I've been somewhat ignorant when it comes to the finer details of pcb layout. Lately I've read a couple of books that try their best to lead me on the straight and narrow. Here is a couple of ...
109
votes
6answers
48k views

Should chassis ground be attached to digital ground?

I'm working on a PCB that has shielded RJ45 (ethernet), RS232, and USB connectors, and is powered by a 12V AC/DC brick power adapter (I do the 5V and 3.3V step down on board). The entire design is ...
60
votes
12answers
75k views

How to connect USB Connector shield?

How should I route USB Connector shield on PCB? Should it be connected to GND plane right where USB is placed, or should the shield be isolated from GND, or should it be connected to ground through ...
45
votes
6answers
131k views

Standard PCB trace widths?

Is there a standard for the sizes of PCB traces? That is are some 25 mil and others 10 mil or is can you choose your own? I plan to run 400mA through some thicker traces, but less than 30mA for all ...
20
votes
6answers
29k views

How do I facilitate keeping multiple grounds, (i.e. AGND, DGND, etc…) separated in the layout when using Eagle?

I've designed several PCBs where I needed to keep the ground returns of different parts of the circuit separated, i.e. analog, digital and high power. I use Cadsoft Eagle for schematic capture and ...
21
votes
6answers
7k views

What's the schematic to share one crystal with two micros?

How do I share a single crystal (not a complete oscillator module) between two micros? Is it OK to just connect everything as normal for the first micro and also directly connect its XO to the XI of ...
10
votes
9answers
3k views

Schematic capture/PCB layout program recommendations [closed]

I'm still using PCAD2006 for my schematic capture and PCB layout. I'm not very happy with this; it is rather buggy, but it's a leftover for which I have an extensive library. Due to the problems I'm ...
9
votes
1answer
3k views

Why is a broken ground plane not as effective as an unbroken one?

I did a two layer board a few weeks ago which had a dedicated ground plane. I routed 90% of the signals on the top layer and for the last 10% I had to route them through the bottom (ground) plane. I ...
30
votes
5answers
24k views

What is causing large oscillations in my DC/DC boost converter? Is this ground bounce or some other effect?

I designed my first PCB for a DC-DC boost converter only to find that it produced very noisy output. The design is based around the MIC2253. Here's a schematic: Although my circuit allows for ...
27
votes
5answers
12k views

Standard PCB Layout Book

Are there any good references on advanced PCB design/layout/routing? There seems to be a large wealth of circuit design books, books about RF PCB design, and books dealing with high-speed digital ...
10
votes
4answers
12k views

Why MOSFET source is indicated with arrow ?

I know that , a basic MOSFET contains source and drain , and either it's a NMOS or PMOS ; it is indicated by an arrow at source . But let's look at a fabricated NMOS. Here we can easily see that ...
16
votes
2answers
3k views

Mixed signal PCB layout for PSoC

I am developing a PCB for an analogue sensing application. It uses the internal ADC on a PSoC3. As usual, the application is very space constrained (11mm x 21mm), so I have had to make some ...
4
votes
1answer
1k views

Dealing with splits in my ground plane

Whenever I'm making a cheap, 2-sided PCB, I run into this problem: Where I have signal lines (on the top layer here) running over top of a big fat power trace (on the bottom layer). Now, this is ...
15
votes
1answer
20k views

How critical is the layout of USB data lines / how does my layout look?

I'm laying out the USB data lines on my board at the moment, and I'm just trying to get an idea of how well off my design is gonna fare. Here are the particulars: 4 layer board (from the top: signal,...
12
votes
1answer
2k views

PCB microcontroller layout in a mixed-signal system

This is a direct continuation of this question. So here's my layout, what do you think about the microcontroller side? UPDATE April 2019: I built the board in spring/summer 2016, but never got around ...
9
votes
4answers
4k views

How important is it to put decoupling caps on the same side of the PCB?

How important is it to have decoupling capacitors on the same side of the PCB as the IC? I am desperately short of space in a design, and it would really help to put the caps on the bottom side. I ...
11
votes
5answers
6k views

How to connect decoupling capacitor when VCC/GND pins aren't close

I'm making a board which will host an ATmega 162 microcontroller in PDIP package. Unfortunately, VCC and GND pins are diagonally arranged. From what I've read, the capacitors should be as close to the ...
8
votes
1answer
27k views

How do I install a KiCad schematic or footprint library?

After I download a KiCad schematic library or footprint library -- such as the ones from http://kicadlib.org/ -- how do I use it in my schematic and layout? Should I install that KiCad library file ...
10
votes
3answers
10k views

Blind/buried vs. through hole vias?

I'm trying to learn PCB design and, from what I've read and seen, there appear to be three different types of vias: Through hole - goes all the way through the board Blind - goes from the top or ...
21
votes
2answers
3k views

Can you place vias inside a QFN footprint?

I am designing a very dense PCB containing a 0.4mm pitch QFN chip. In parts it is proving very difficult to fan out. It is made all the more difficult by the huge thermal pad that all QFNs have for ...
8
votes
1answer
4k views

How is my crystal layout looking?

I've done a preliminary layout of my crystals. I've never designed a board with crystals so this is just a rough first pass based on my small set of working knowledge of crystal layout. How am I ...
6
votes
1answer
276 views

Review of my first ever PCB design for a watering control robot.

I'm building a small watering control for one of my large indoor plants. This is my first real electronics project outside of school. Although I studied EE at university and did my basic component and ...
3
votes
1answer
867 views

27512 pinout and PCB layout

I'm trying to design PCB traces for a 27512 EPROM chip. But its pinout for the higher half of the address bus seems completely illogical to me and I cannot imagine how should I lay out my traces for ...
2
votes
2answers
422 views

Texas instruments component size

I am about to make a pcb footprint for this package: http://www.ti.com/lit/ml/mpds049b/mpds049b.pdf But I am not sure what the two numbers mean, for example at pin 5 that 0,30/0,15. Are these maximum/...
1
vote
2answers
701 views

Weird capacitor looking things shows up in altium when I zoom into the pcb layout

I am using altium for first time for my little circuit project. My layout start showing these weird capacitor looking things in PCB layout. What exactly are they and what are they used for and how do ...
0
votes
2answers
432 views

Placement of varistor with respect to fuse

My design includes a pretty standard AC/DC converter powered by mains for intended use at home. For overvoltage and overcurrent protection, I am planning to use a combination of varistor and fuse ...
0
votes
1answer
439 views

Altium Designer - split plane

I want to make a plane for my supply on my PCB and a plane for my MCU to isolate the MCU from the power supply noise. I found this article in Altium designer resource: But it isn't clear how the ...
22
votes
4answers
17k views

Are there reasons *not* to have a copper-pour ground plane on a PCB?

I am taking a first stab at designing a PCB from scratch. I am considering using a CNC mill fabrication process, and it seems like with this process I would want to remove as little copper as possible....
14
votes
6answers
1k views

What are some 'gotchas' of high-frequency board design?

I'd like to design a PCB for an analog loop controller.. something with an A/D, D/A, and processor on board. (Either DSP or FPGA, I haven't decided.) Since this should modulate analog signals at 10 ...
13
votes
3answers
16k views

Ethernet Layout Guidelines

I'm working on a DC jack powered Ethernet design and I've downloaded many Ethernet Layout guidelines from many semi vendors with varying recommendations. I've read app notes recommending almost every ...
18
votes
4answers
4k views

Can I run traces through “No Connection” pins?

Several ICs are manufactured in packages with more pins than it supports. For example, the LM317 in an SO8 package has 4 VOUT pins and 2 N/C (no connection) pins. I often want to run traces through N/...
6
votes
3answers
4k views

Layout of decoupling capacitors

So I've been attempting to create my first development board and layout. I'm first working on the decoupling capacitors, power and ground portions of the layout. The MCU I'm trying to properly ...
10
votes
2answers
3k views

Single ground plane vs split planes?

I have seen conflicting sources about ground plane design. I have been told at my work many times, just slap a single massive ground plane in and that works well enough, we don't deal with anything ...
9
votes
3answers
4k views

SMPS PCB Design Critic

Oldest versions of this post can be viewed through this link. This is my re-designed layout. What is your view again? 10-32V to 5V 1.2A SMPS Buck Regulator Design. The IC is IFX91041 from infineon. ...
5
votes
2answers
2k views

Learning PCB Layout Strategy

A number of projects I have been working on have outgrown the breadboard phase, and I have been learning how to do PCB layout. My first tiny project (a cable adapter) went smoothly, but as I have ...
5
votes
3answers
10k views

CAN bus layout design

I am trying to design a CAN bus node. The CAN bus shall be split-terminated with 120Ohm, 60Ohm for each line. Therefore i tried using this paper to calculate a characteristic impedance of 60Ohm for a ...
11
votes
1answer
12k views

How to connect ground planes together

What is the best way to connect ground planes together ? I know that ground planes are connected together at multiple locations in order to keep a low impedance GND across the whole board and provide ...
7
votes
3answers
5k views

For a 4 layers PCB (with ground plane), covering with ground polygon on Layer 1&4 necessary?

For a single or double layered PCB board, usually I will cover all the empty spaces in the layout with Ground. This is the 1st time I am designing a 4 layer PCB layout. Layer 1: top signal (high ...
6
votes
2answers
2k views

Power Plane and Decoupling Capacitors Routing

Forgive me for my simplicity. I'm just a hobbyist and not an engineer by trade. I am trying to make my first 4 layer PCB in Eagle and I have a question I cannot find the answer to regarding power ...
5
votes
4answers
1k views

What precautions should I take when mixing analog audio and digital on the same board?

What precautions should I take when mixing analog audio and digital (uC control) on the same board? I don't want to hear the I2C bus in my speakers. I'm thinking about Separate power supplies ...
9
votes
3answers
4k views

DDR1 Layout Considerations - DOs and DONTs

I am novice to high speed design. Before getting in to DDR, I recently learned about impedance matching and how it is done, likewise I learned about length matching and how it is done.(Baby steps ...
7
votes
2answers
863 views

PCB Panelization tool/SW and adding test connections

I prepared 4 different PCB layouts on Eagle CAD and generated Gerber files. As I can see Eagle CAD doesn't have any option to panelization. Is there any free tool/program that can allow me to ...
7
votes
1answer
1k views

DDR bus design review

In our last build we had issues with DDR stability in our prototype, simply because of lack of experience with this type of high speed memory connections. We managed to get it working with halving the ...
5
votes
4answers
355 views

Placement of undervoltage monitor and cutoff

Suppose I have a circuit running at 3.30V, supplied via an LDO regulator (e.g., ADP124), powered by a Li-ion battery. In other words: Now, I would like to implement an undervoltage cutoff to "turn ...
10
votes
2answers
16k views

EAGLE Matched Length Pairs / Groups

What facilities does EAGLE CAD have for helping to do layout with matched length groups and differential pairs? Can you apply such a constraint in the auto-router? As a follow-on to this, what (other) ...
9
votes
1answer
1k views

Is there a PCB-layout related reasoning behind DDR memory package and footprint?

BGA DDR packages have a unique footprint. There are two columns of pads on both sides of the device, and an empty column in between. Is there a reasoning behind the placement of these pads (in terms ...
5
votes
4answers
6k views

Altium PCB Layout: The Difference of Through Via, Micro Via, and Burried Via

This is my very first time doing 4 layers PCB layout. What is actually the difference between Micro Via and Buried Via? Say I have Layer 1, Layer 2, Layer 3, Layer 4. What I know I use the Through ...
2
votes
1answer
1k views

SMPS PCB Design Critic 2

Thanks for your patient help, I am learning a lot. This is my (final, I hope) re-designed layout. What do you think? 10-32V to 5V 1.2A SMPS Buck Regulator Design. The IC is IFX91041 from infineon. ...
11
votes
2answers
1k views

EMI Issue: Ringing in switch mode power supply layout (5V -> 3V3)

I am working on a device which is undergoing testing to pass FCC part B (CSRR 22) emissions. At one angle and polarization (Vertical) the device fails as it has emissions in the 100-200Mhz range which ...
9
votes
3answers
3k views

PCB layout for high side switch (high current)

I'm working on a PCB layout for two high side switches. You can see below a picture of my current layout. The copper weight of the future PCB will probably be 2 oz/ft² (double sided). I use two p-...