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CM3 on 2 layer PCB

Posted: Fri Jan 25, 2019 8:46 pm
by javaraspi
Hello community, good afternoon.

I am currently working in a project that includes CM3 module.
The design makes use of the following peripherals:

- USB Port
- Camera Port
- SPI Port
- Some digital I/O for status and control

Is it possible to have it running in a 2 layer PCB design?.

Thanks for you help,

Javier.

Re: CM3 on 2 layer PCB

Posted: Sun Jan 27, 2019 7:23 am
by John Westlake
Hi Javier,

Its really a question about your PCB design skills and a bit of luck...

If you can run the USB lines and camera port without other tracks crossing them (so solid Ground Plane below and surrounding the differential USB and Camera Port tracks then you should be OK.

Its really a question of unbroken Ground plane and good tight local PSU decoupling... it can be done on a 2 layer PCB but its hard.

For you information - these past few years we have been using JLC PCB for mutlilayer boards - there price is so good (even for prototypes) that it makes considering the cost savings of 2 layer PCB's questionable... You also have to factor that 2 layer PCB's are manufactured by lower-end PCB company's - with 4 layer PCB's being higher quality (tighter tolerances, higher resolution etc).

How many extra design hours and prototyping cost is involved with going 2 layer - is the cost difference really worth it?

https://jlcpcb.com/

Re: CM3 on 2 layer PCB

Posted: Tue Jan 29, 2019 4:53 pm
by javaraspi
Hello John thanks for your answer.

You are right, the cost diference between 2 and 4 layer, considering the additional work hours and reliability of the design becomes marginal.
I think I will go ahead with 4 layer.

Does this stacking sounds good to you:

1st Layer -> Signals for USB & Camera
2nd Layer -> GND
3rd Layer -> All PWR Supplies
4th Layer -> Digital I/O & SPI Port

I noticed that the Compute Module IO Board has 6 Layers.

Thanks again for your help.

Javier.

Re: CM3 on 2 layer PCB

Posted: Tue Jan 29, 2019 4:54 pm
by javaraspi
Hello John thanks for your answer.

You are right, the cost diference between 2 and 4 layer, considering the additional work hours and reliability of the design becomes marginal.
I think I will go ahead with 4 layer.

Does this stacking sounds good to you:

1st Layer -> Signals for USB & Camera
2nd Layer -> GND
3rd Layer -> All PWR Supplies
4th Layer -> Digital I/O & SPI Port

I noticed that the Compute Module IO Board has 6 Layers.

Thanks again for your help.

Javier.

Re: CM3 on 2 layer PCB

Posted: Sat Feb 02, 2019 6:12 pm
by aBUGSworstnightmare
4 layer design should be fine for your use case

Re: CM3 on 2 layer PCB

Posted: Tue Feb 05, 2019 6:31 pm
by javaraspi
Hello aBUGSNighmare,

Excellent. Thanks for your comments!