Hardware design and antena

[FormerMember]

Designing a custom pcb, we have a few questions, and maybe you could help a little bit.

On this Nordic design ,before proceeding to layouts :

1. Can I skip pins 45/46/47 and not puting L2/L3 ? I did not see them on other designs.(what are they?)
2. If I won't use NFC, can I skip all the parts on pins 11/12 and simply use them as outputs ?
3. Can we locate the chip on one pcb side and the antena right on the other side beneath the chip? ( extreme size constrains on pcb..)
4. Can I flash this design using nrf52 dev kit on the debug connector ?

Are there any specific pins that can't do specific things ? (I could see serial/I2C/SPI/PWM works on all of them)

Thank you !

[Jørn]

Hello rani

1.As Darren Beckwith mentioned the inductors L2 and L3 are needed for the DC/DC regulator, see page 78 of the nRF52832 product specification. These can be omitted if you are not using the internal DC/DC regulator, see the reference schematics pages 545 and 546 of the product specification.

See edit below

3.Yes it is possible to do that, see devzone.nordicsemi.com/.../ The environment of the antenna, as well as the via hole will affect the impedance observed at the output of the T-network, and a matching network is needed to compensate for this. If you are using a PCB trace antenna you can use a single shunt capacitor in combination with tuning the antenna length. If it is a chip antenna (as in the link) you will need a pi network. See the following blog post and the links provided there. devzone.nordicsemi.com/.../ It is for the nRF51 but the antenna matching methods still applies.

Also be sure to read the PCB guidelines, page 551 of the product specification for considerations when doing the layout.

EDIT: 26.04.17: As pointed out in the comments by dingari I may have misunderstood the question in the original post. Placing the antenna directly below the chip really isn't recommended as the antenna needs a keep-out region around it, meaning no traces, or components on any layer on the PCB within a certain distance from the antenna. In the case of a PCB monopole, there should also be a ground plane reaching out from the feed point of the antenna. This ground plane should be as whole and large as possible. Please see the white paper on monopole antennas for 2.4GHz infocenter.nordicsemi.com/.../nwp_008.pdf

Best regards

Jørn Frøysa

[dingari]

Regarding #3, I think you misunderstood the OP. He is asking whether it's possible to locate the antenna directly below the nRF5 chip. Every antenna datasheet I've looked at requires no ground and no traces of any kind below the antenna.