Questions tagged [layout]

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

Filter by
Sorted by
Tagged with
228
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
130k 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 ...
37
votes
5answers
6k views

Why should you use two resistors in parallel on an LED?

So I was looking over the Arduino R3 schematics and noticed this little design choice: What is the reason for doing something like this? I mean it's hard to know what the designers were thinking, but ...
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 ...
28
votes
9answers
19k views

Do you layout in mil or mm?

I have been using 10 mil trace with 10 mil spacing. The PCB vendors quote that they like traces down to 7 mil. But then I ran across a PDF showing how to fan out a QFP to get all the signals ...
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 ...
25
votes
6answers
9k views

Have I placed too much on this PCB layout?

I am doing my first PCB layout (using Altium) and have finally gotten past the auto-router stage. The result is a mess and there are some missing nets and design rule violations. Have I packed too ...
24
votes
1answer
4k views

PCB layout questions for MCU breakout board

I'm attempting to route a board that is, essentially, a breakout for the LPC23xx/LPC17xx MCU. I've never routed anything approaching this complexity before, and I have a few areas of concern. I know ...
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....
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 ...
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 ...
20
votes
3answers
2k views

What's the purpose of traces that are later punched out?

I've found this odd feature on an FPC in a Camera than handles button and switch input. You can see there are traces that look like they were once connected and later punched out to be cut. The one ...
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 ...
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/...
18
votes
5answers
3k views

Can a switching power supply be built on a breadboard?

I'm toying with the idea of putting together a switching power supply (my first), using something like the LT1076-5 or the LM2576 controller ICs. These ICs have low external parts counts, and a ...
18
votes
1answer
3k views

PCIe, diagnosing and improving an eye diagram

I have implemented a design that uses PCIe. It is somewhat different in that the PCIe interface is used as a chip-to-chip communication lane on a single PCB (e.g. no PCIe connector). The root ...
18
votes
1answer
1k views

Designing for High Acceleration

I'm looking into designing a board for a robotics application that is going to be spinning very quickly, and am wondering if there is anything special to take into account. It's going to be in the ...
16
votes
4answers
3k views

When laying out circuit board traces, what impedances do I need to consider?

I do low-speed circuit design for microcontrollers and such (usually at less than 20 MHz), and now I'm getting started on some more high-speed circuits. What I want to know is: What considerations ...
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 ...
15
votes
3answers
5k views

I painted myself in a corner. How to layout?

I'm a hobbyist working mostly in DC projects. For development and testing, I use breadboards, and later a perforated board. My projects are normally low count: an Arduino Nano/Pro Mini + a few ICs. ...
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,...
14
votes
5answers
1k views

Circuit board without EDA

For me there is no doubt that one of the most time consuming tasks when it comes to produce a new board is going from a ratsnest to the final layout. I must admit I am not an expert, but to me it ...
13
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
2answers
3k views

Mounting components on both sides of a PCB

I'm designing a PCB with a microcontroller ,CAN transceiver, sensor (I2C) and linear regulator. I want to make the PCB as small as possible, so my thoughts were to use both sides of a two layer stack ...
13
votes
2answers
2k views

What is the purpose of copper planes in a switching power supply?

I'm looking at including a buck converter to power a 3.3V microcontroller, and I used TI's Power Designer to generate a recommended layout for my parameters. I noticed that the copper planes are ...
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 ...
13
votes
1answer
2k views

TVS Diode Layout

I have two DB37 connectors on my board which ultimately connect to a CPLD. All of these connections/signals are inputs to the device. To protect from ESD I am using TVS Diodes ESD9C3.3ST5G. I have ...
12
votes
4answers
36k views

How to easily find or create parts for Eagle schematic/board layout

For Eagle CAD software, during schematic or board layout, how can I search for parts/footprints already created by other people out there, to make my life easier? And if I'm still unable to find what ...
12
votes
3answers
7k views

Is it better to have a poor top layer copper pour or no copper at all?

For a few small 2 layers boards I'm doing, I'm using the top layer for parts and signals and a ground pour on the bottom layer with no or very short traces, based on comments and answers to my ...
12
votes
2answers
4k views

How many ground and power pins to have in a connector?

I'm designing a daughter board for a project. There are 35 I/O pins that need to go to the board. How do I determine the number of ground and power pins to include? How do I determine the placement of ...
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 ...
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 ...
11
votes
4answers
4k views

Layout advice for LDOs

I'm developing a four layer board which is powered by 3 voltages - 1.8V, 3.3V and 5.0V. The board has the following stackup: Signals Ground 3.3V Signals The ground and 3.3V plane are completely ...
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 ...
11
votes
4answers
701 views

Which is the preferred approach to PCB layout for signal vs power traces in analog circuits, and things to consider?

I have had to layout 2 layer PCBs several times now for analog signals, and am just beginning to learn the process. I often face a similar question in one form or another with regard to laying out ...
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 ...
11
votes
2answers
2k views

What is causing the spikes or oscillations in my Buck-Boost converter?

Currently, I have a problem about the Buck-Boost converter. The schematic of my Buck-Boost converter can be seen as below: I used the Hall Effect transducers, LV25-P and LA25-NP, to measure the input ...
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 ...
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 ...
10
votes
2answers
2k views

Quad SPI PCB layout

I am trying to make a good layout for the Quad SPI NOR flash memory MT25QL256ABA1EW9-0SIT with the STM32 MCU. My problem is that I find the memory chip pinout quite inconvenient. I have managed to ...
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 ...
10
votes
3answers
2k views

A decent library of component simulation, schematic and PCB layout?

I am truly a novice in PCB design, so I am new to all aspects of it. What I am having the most trouble with is actually picking suitable components. The trouble I am having is that I am not really ...
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) ...
10
votes
1answer
1k views

How close do I really have to place a 25MHz crystal?

I'm laying out a very space constrained PCB. Normally I would place a 25MHz crystal absolutely as close as possible to the chip using it. However, on this PCB, something else really needs the space ...
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 ...
10
votes
1answer
27k views

Multiple fingers vs single finger layout (MOSFET transistor)

Please, provide a summary of advantages and disadvantages of a transistor layout with multiple fingers (MF) vs single finger? When laying out a MOSFET with a particular width and length, in an EDA ...
10
votes
3answers
7k views

Choosing a SDRAM pcb layout

I'm working on a project with the quite new STM32F429 in LQFP208 package. I need to solder the first couple of prototype by myself for low budget reason. I choose this package so I could check myself ...
9
votes
3answers
2k views

Design of 50 ohms RF trace for 2.4GHz…Double layer FR-4 PCB

I will use a 2.4GHz transceiver on my new project. The PCB material will be FR-4 with 1.6mm thickness and the connector is a SMA. My doubt is about the RF trace that should have 50 ohms impedance. ...

1
2 3 4 5
12