NRF51822 PCB layout review

RE: NRF51822 PCB layout review

Einar Thorsrud — Tue, 13 Sep 2016 08:34:50 GMT

This seems much better than the initial board. I have few comments, though:

You should have a pi-network to tune the antenna, as it is always required in practice in order to get good performance (regardless of what the antenna manufacturer claims). In order to make room for it you probably need to move some components.
In general it is a good idea to use all empty space for ground, so I would put ground copper on the power layer as well.
I have not compared the placement of your balun to the reference design in detail, but from looking at your layout it seems OK. If you have not done so you should measure trace lengths etc., as it is important to exactly copy the placement of the balun relative to the nRF.

RE: NRF51822 PCB layout review

dingari — Mon, 12 Sep 2016 14:28:42 GMT

Hi, I've uploaded gerber files here: www.dropbox.com/.../gerber.zip - I started out with two layers, but since the board is so crowded I had to add a seperate ground plane. Since you don't really make three-layer boards I utilized the other inner layer for the supply voltage traces. There aren't a lot of traces on that layer, would you recommend filling the extra space with ground copper or leave it blank?

I'm planning to use the Johansson 2450BM14E0003T balun, listed here: www.johansontechnology.com/nordic

RE: NRF51822 PCB layout review

Einar Thorsrud — Mon, 12 Sep 2016 13:17:11 GMT

This seems much better than the initial board, but it is difficult to see all the details of the layout in the pictures. It would also be interesting to see the other planes, particularly the ground plane. Can you upload Gerber files, which would make it easier to review it?

Also:

Which balun do you use? It must be one of the supported baluns. Remember to take care to copy the placement of the capacitor (your C20) exactly as the reference design.
Even though the antenna datasheet states that "No external matching required", this is generally only true if your board is close to identical to the antenna reference layout. In practice, most boards require a pi network in order to tune the antenna, so you should include that.