javaraspi
Posts: 15
Joined: Fri Jan 25, 2019 8:32 pm

CM3 on 2 layer PCB

Fri Jan 25, 2019 8:46 pm

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.

John Westlake
Posts: 104
Joined: Thu Nov 09, 2017 4:34 am

Re: CM3 on 2 layer PCB

Sun Jan 27, 2019 7:23 am

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/

javaraspi
Posts: 15
Joined: Fri Jan 25, 2019 8:32 pm

Re: CM3 on 2 layer PCB

Tue Jan 29, 2019 4:53 pm

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.

javaraspi
Posts: 15
Joined: Fri Jan 25, 2019 8:32 pm

Re: CM3 on 2 layer PCB

Tue Jan 29, 2019 4:54 pm

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.

aBUGSworstnightmare
Posts: 1451
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3 on 2 layer PCB

Sat Feb 02, 2019 6:12 pm

4 layer design should be fine for your use case

javaraspi
Posts: 15
Joined: Fri Jan 25, 2019 8:32 pm

Re: CM3 on 2 layer PCB

Tue Feb 05, 2019 6:31 pm

Hello aBUGSNighmare,

Excellent. Thanks for your comments!

Return to “Compute Module”