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Long time lurker first time poster. I am making a breakout for a MCU we want to prototype with and I was curious if there are design rules I should follow for these.

The datasheet for the MCU says "0.1 µF ceramic at each pin plus bulk capacitor 1 to 10 µF" for each power pin. But since I am tying all the power pins together can I get by with one or two bypass caps and a bulk cap?

I have attached images of my board layout and the datasheet section in particular.

Please ignore the silkscreen I am working on that last once placement of parts is done.

https://imgur.com/a/XkTFsxl

Board Layout with top plane (Power Plane) showing

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  • \$\begingroup\$ I'm voting to close this question as off-topic because it is an overly broad design review. \$\endgroup\$ Dec 26 '19 at 14:37
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    \$\begingroup\$ The high frequency bypass caps should be unique to each pin pair and placed as close as possible to the pads because their performance is limited by inductance, both trace inductance and that of the capacitor packages themselves. \$\endgroup\$ Dec 26 '19 at 14:38
  • \$\begingroup\$ @ChrisStratton Disagree - plenty of PCB reviews, especially simple ones for new users. \$\endgroup\$
    – awjlogan
    Dec 26 '19 at 15:49
  • \$\begingroup\$ Can you post a schematic as well to compare against? Silkscreen would also be helpful to see what corresponds to what :) \$\endgroup\$
    – awjlogan
    Dec 26 '19 at 15:50
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    \$\begingroup\$ @ChrisStratton - this is someone's first time posting, why not make that point directly rather than just say you want to close it for a reason opaque to a new user. Anyway... \$\endgroup\$
    – awjlogan
    Dec 26 '19 at 16:15
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Generally looks ok, and welcome :) Few things:

  1. Make sure all your pin headers are on 0.1" spacing. Even if you're not putting it on a breadboard, this will make sure any header cables will fit nicely. See, for example, the 3 little connectors toward the bottom left.
  2. The component to the top right seems to have a trace going from a via through the ground plane to the bottom pad. This doesn't seem to be on the same net as the plane, so could be a short.
  3. Each power pin on the MCU package must have a capacitor on it, usually 10-100 nF will do. Use as small a component size as you feel comfortable soldering. Put a 10 uF for each supply voltage where it comes into the board. This is very much rule of thumb, but should get you started!
  4. Some of your trace bundles could be tidied up. For example, the bottom right one has the right most trace going out to the right then down. If you went down first to meet the other traces in the bundle, the ground plane can fill in to the space. The bottom left one is nice.
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  • \$\begingroup\$ I've generally had a lot of luck with far vaguer and fewer bypass caps than people normally recommend. Not saying I'd do that when you have the option, but I've soldered up several successfully to basic lqfp break outs... What MCU is it? If it's an arm one, put the arm 10 pin jtag/swd header on it so you can plug a programming ribbon in easily. If your planning on trialling the adc or any specific features then you might want to add sample buffer caps on the adc ins. You might want to put a crystal and caps in... \$\endgroup\$ Dec 26 '19 at 21:00
  • \$\begingroup\$ You might want to put the pins all in 2 lines to enable breadboard plugging... Lastly, regenerate your fills. It's not clear what is attached to power and ground. IIRC on KiCAD you press "b". \$\endgroup\$ Dec 26 '19 at 21:00

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