Custom PCB design for nRF52840

RE: Custom PCB design for nRF52840

Kaja — Thu, 19 Aug 2021 06:48:33 GMT

Hi Fernando,

you can have a look at:

Monopole, printed PCB antenna: This is easy to make and easy to tune, you also only need one impedance matching component, so it’s cost effective. Here the spacing is the issues, you need to make it about 23 mm long needs a minimum of 5 mm clearance to the ground plane. High bandwidth, making it fairly resistant to detuning. Link to our whitepaper: https://infocenter.nordicsemi.com/pdf/nwp_008.pdf?cp=12_18

This is the type of an antenna we use on our DK, you can also copy the antenna directly from the DK files, but you should add some mm of length, for antenna tuning, for your specific design.

Best regards,
Kaja

RE: Custom PCB design for nRF52840

Fernando Fontes — Wed, 18 Aug 2021 09:40:49 GMT

Hello Kenneth,

Thank you for the answer.

I think I'm getting it :). One last question, is there any antenna design file for this specific nordic device? I'm thinking of having a PCB printed antenna with the option to switch to a uFL connector with an external antenna if needed.

Thanks in advance,

Fernando

RE: Custom PCB design for nRF52840

Kenneth — Tue, 17 Aug 2021 13:21:49 GMT

[quote user="Fernando Fontes"]Are the EXTSUPPLY, DCDCEN0, and DCDCEN1 registers related to the internal regulator of the NRF52840 right? So, I don't need them.[/quote]

Correct.

[quote user="Fernando Fontes"]Which one is the most updated version?[/quote]

Always check the latest reference design files from the product page:
https://www.nordicsemi.com/Products/nRF52840/Compatible-downloads#infotabs

Best regards,
Kenneth

RE: Custom PCB design for nRF52840

Fernando Fontes — Tue, 17 Aug 2021 07:49:19 GMT

Hi Kenneth,

Thank you for the reply. Well, I think that 25mA is enough. However, it's best to give a margin and give the option for future expansion. For that reason, I'm trying to use an external dc-dc regulator to power everything. I went to this page https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Fref_circuitry.html&cp=3_0_0_6_2 and I think that option 6 is the best fit for me. Can you help me to confirm that? Are the EXTSUPPLY, DCDCEN0, and DCDCEN1 registers related to the internal regulator of the NRF52840 right? So, I don't need them.

My last question is related to the antenna port. I noticed different values for the passive components in the eagle design files and also some circuitry differences between options 6 and 7 for instance. Which one is the most updated version? I want to use an external antenna...

Best regards,

Fernando Fontes

RE: Custom PCB design for nRF52840

Kenneth — Mon, 16 Aug 2021 10:14:44 GMT

If the regulator specifications for the internal 3V3 meets your requirements in terms of tolerance and maximum external current draw that should be fine:
https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html#unique_392235502

Kenneth

RE: Custom PCB design for nRF52840

Fernando Fontes — Fri, 06 Aug 2021 16:21:18 GMT

Hi Kenneth,

Thank you for the reply. I have another question regarding the power supply. What do you think is better, having an external 5V regulator and use the nrf52840 internal voltage regulator for the 3V3 or just having an external regulator for the 3V3 and skip the nrf52840 internal voltage regulator?

Thanks in advance,

Best regards,

Fernando

RE: Custom PCB design for nRF52840

Kenneth — Wed, 28 Jul 2021 11:14:14 GMT

The 32MHz is required for radio operation.

I don't believe an external 32kHz crystal is needed, you should be able to use the internal 32kHz RC oscillator instead (for watchdog and timing), but I can double check.

Kenneth