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I am designing a control board for an analog audio amplifier, with a touch screen interface.

This is my first board I have ever laid out and routed and I was just wondering if people check my design look before I send it out to get it printed.

Quick rundown of the connectors on the board:

  • J7 is the 18v AC coming in from a transformer
  • J2 is a 20 pin jtag connector
  • JX is connected to a LCD / Touch screen module
  • J3R & J3L are control lines going to a digital potentiometers to control the gain and the volume

Below is the BOM

enter image description here

Screen capture of the board it's a four layer board with the top inner layer being a ground plain.

enter image description here

Let me know what ever you think. Like I said this is my first time laying out a board so I did use the auto router and the fixed it in some places. I would rather be brutally honest and tell me to redesign if need be, before I waste $66 on a board that isn't going to work.

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    \$\begingroup\$ And one word of advice, DO NOT EVER USE AUTO ROUTER. A professional will never do that and it is a good learning practice. Just think of it as drawing, the more effort you put on it better the outcome would be. \$\endgroup\$ – David Norman Jun 16 '13 at 23:50
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    \$\begingroup\$ Why say "DO NOT EVER USE AUTO ROUTER"? Professionals use routers every day for ASICs, because they can far out-perform humans for large designs. \$\endgroup\$ – travisbartley Jun 17 '13 at 1:13
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    \$\begingroup\$ This question lacks a direct inquiry. JWL, we can give better support to you if you can narrow your question down and be more specific. Unfortunately, this site isn't made for "what do you think" questions. \$\endgroup\$ – travisbartley Jun 17 '13 at 1:15
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    \$\begingroup\$ @David: Nonsense. A auto-router is a useful tool. Like any tool, you have to know what it can do, when it's appropriate to use, when not, and how to control it properly. It is very rare that I don't use the auto-router on at least part of a board I am designing. Saying to never use this tool is bad advice and sounds more like a religious conviction in the first place. \$\endgroup\$ – Olin Lathrop Jun 17 '13 at 12:43
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    \$\begingroup\$ If you really think auto routers are of no use, then try to route 10,000 logic cells with >90% placement density over 7 metal layers. Oh, and make sure your routing doesn't create any design rule violations, timing violations, or signal integrity problems. And you have less than 5 minutes to do it. If you can't do that, you shouldn't say such sweeping statements, because an auto-router can. \$\endgroup\$ – travisbartley Jun 18 '13 at 1:44
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Just a couple of random points. I didn't do a complete analysis, mostly because what I saw was serious enough to not warrant that.

  1. Switch to SMD ceramic caps. The lead inductance of TH caps makes them practically useless (talking about the normal 0.1 uF caps, not bulk caps).
  2. Might as well switch to SMD resistors, too.
  3. Power traces look very thin. Especally the lines going to the linear regulators.
  4. I have no confidence that you calculated the thermal dissipation of the linear regulators, or that you have a way to cool them.
  5. The vias look very large. Might be able to make them smaller to give you better signal routing.
  6. It is very hard to tell from the picture, but I think that you have vias so close together that they are forming slots/voids in the power/gnd planes.
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The layout of the crystals doesn't look right.

  1. Per BOM, the X1 is in the R145 package (it's a cylindrical package). In the layout it looks more like HC-49 package.
  2. There a tips for the PCB layout for the crystal on the p.17 of the ST app note AN2867. More discussion on the layout for the crystal can be found in this thread.
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  • \$\begingroup\$ @JWL Did you auto-route this board? \$\endgroup\$ – Nick Alexeev Jun 17 '13 at 2:18
  • \$\begingroup\$ Yes, At the time I didn't know that it was such a bad idea to do that. I going to try to relay out the board with only 2 layers and hand route must of the thing. \$\endgroup\$ – JWL Jun 17 '13 at 2:45
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    \$\begingroup\$ Using an autorouter for one's very first board is indeed not a good idea. Autorouter has it's uses. But, beginners usually over-use autorouter. \$\endgroup\$ – Nick Alexeev Jun 17 '13 at 2:59
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You can use more wide tracks if you have no specific space constraint. Specially power and ground tracks must be as wide as possible. And ofcourse SMD capacitors are more suitable than TH and important thing is that capacitors must be place as close as possible to microcontroller and filtering capacitors to power regulator (if using) ,,, and their must be wide

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You should also try to avoid right angle traces. This will cause an edge on the signal, if you were to hook an oscilloscope to it, which may cause issues

Watch this from sparkfun to cover many of the basics.

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