Hi,
I started designing a Custom PCB based on various Arduino/Adafruit boards. For most of it I genuinely took over the available designs online. While doing general research though, I realised how specific condensator values have to be selected considering the length/width of the copper trace and the specific inductances of all components.
- Can I stick to the values written on the available schematics, or should I consider re-calculating everything ?
- Does anyone can advise me a good source for best practices of PCB design ?
- I need to remake an SPI SD Card Reader, but I can't understand the schematics of the levelshifter as they are represented very differently there and on the constructor's datasheet.
Thanks a lot for your help !
Gerneral questions about custom PCB making
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Please be positive and constructive with your questions and comments.
- argonblue
- Posts: 94
- Joined: Wed Apr 25, 2012 12:18 am
Re: Gerneral questions about custom PCB making
There seems to be errors on the datasheet diagram: the 4Y label for the 4050 is missing, and 5Y for the 4050 should be next to /5Y for the 4049. This datasheet has less-confusing diagrams.I can't understand the schematics of the levelshifter as they are represented very differently there and on the constructor's datasheet.
If you're referring to the Adafruit schematic placing the individual level shifter symbols separately instead of together in a single box like the datasheet, that's a common practice so that they can appear where it's easier to see their purpose in the circuit. The labels like IC1A, IC1B, etc indicate that they're all subunits of the same IC package.
If you're wondering why the datasheet diagram you posted has negation bubbles and the Adafruit schematic doesn't, it seems to be because the 4049 is an inverting level shifter, and the 4050 is non-inverting, and that datasheet diagram tries to represent both on the same diagram. (Again, that particular datasheet is confusing and seems to have errors. Please see the link I posted above for a better one.)
- adafruit_support_mike
- Posts: 67485
- Joined: Thu Feb 11, 2010 2:51 pm
Re: Gerneral questions about custom PCB making
Trace length and shape become important for signals in the RF range.. usually 100MHz or faster. Below that speed, their effects are so small you can safely ignore them.
Trace width depends mostly on the resolution of the process you choose. Wide traces with wide spaces between them are easier to make, and have better adhesion to the substrate. Narrow traces with tight spacing let you pack more signals into a square centimeter of board space, but are harder to make and easier to damage. Most boards use 12mil traces with 12 mil spaces unless they have a specific reason to use something else.
Dave Jones from the EEVBlog has written a good reference:
http://www.alternatezone.com/electronic ... alRevA.pdf
Trace width depends mostly on the resolution of the process you choose. Wide traces with wide spaces between them are easier to make, and have better adhesion to the substrate. Narrow traces with tight spacing let you pack more signals into a square centimeter of board space, but are harder to make and easier to damage. Most boards use 12mil traces with 12 mil spaces unless they have a specific reason to use something else.
Dave Jones from the EEVBlog has written a good reference:
http://www.alternatezone.com/electronic ... alRevA.pdf
- Demokrato
- Posts: 3
- Joined: Mon Jun 27, 2022 8:03 am
Re: Gerneral questions about custom PCB making
Thanks a lot to both of you,
The Dataseet you sent me is a lot clearer indeed argonblue, il all makes sense now.
Also your very complete pdf Tutorial is much clearer/ more complete than most sources i could find so far !
The Dataseet you sent me is a lot clearer indeed argonblue, il all makes sense now.
Also your very complete pdf Tutorial is much clearer/ more complete than most sources i could find so far !
Please be positive and constructive with your questions and comments.