Reference Layout about BLE (nRF52840 & nRF52832)

[Webster Yang]

Dear Nordic Teams : 

I find the layout guideline shows the C3 return path for filtering the harmonic.

The GND pin is connected to the IC's system ground directly. Do I need to separate the pin from IC's GND to prevent the noise coupling?

[Kenneth]

Hi,

C3 should be grounded only to the center pad via the VSS_PA pin, like this the reference layout(s) show:

https://www.nordicsemi.com/Products/nRF52840/Compatible-downloads?lang=en#infotabs 
https://www.nordicsemi.com/Products/nRF52832/Download?lang=en#infotabs 

Best regards,
Kenneth

[Webster Yang]

The pin assignment of nRF52840 aQFN73 B7 is VSS/Power, GND and F23 is VSS_PA/power, Ground (radio supply).

I think the B7 & F23 are RF GND and they might be independent of system GND. The reference layout connects the system GND and RF GND together.

[Kenneth]

I don't see a question here, but just follow the reference layout and pcb guidelines, and for instance placement of vias and clearance of ground like the reference layout and you will be good. You can in any case ask someone here to perform a layout review for you.

Kenneth

[Webster Yang]

I find there are large 3rd harmonic power on DEC4 both on my PCB and DK. You mention the B7 pin is for filtering harmonic gnd, but it is still connected with system gnd. Whether noise would be coupled to other nets or traces through the GND?

[Kenneth]

If you have problems with the design, please make a new case for someone to review your design.

Kenneth

[Webster Yang]

Actually I find the situation on the DK, so I want to check the status on DK. Could you help to confirm the situation what I mention above?

[Kenneth]

Can you share your measurement and how you have measured? What version is this of nRF52-DK?

Kenneth