nRF5340 + nRF21540 connection

RE: nRF5340 + nRF21540 connection

ketiljo — Wed, 25 Aug 2021 12:14:26 GMT

Since you now have an external 3 V regulator, the easiest is to use the nRF devices in normal voltage mode with both VDD and VDDH connected to +3V0. This will guarantee the same voltage on all logic levels.

RE: nRF5340 + nRF21540 connection

Jose Pablo Castro Valverde — Wed, 25 Aug 2021 00:40:18 GMT

Hi Ketiljo

I added this regulator to supply +3V0 voltage:

I got another question.

What about Push Button signal like these two:

Can both be connected to the VDD_nRF port of the nRF5340/nRF52833 or should I change it to +3V0 too?

I want to use the minimal amount of components, that's why I am using the configuration no. 1 for 52833

and configuration no. 4 for nRF5340:

I almost forget, I got three LEDs connected too:

Based on what have you told me I'm thinking I should connect these LEDs to +3V0 instead of VDD_nRF.

I am using 4 layer PCB and I make sure there's only ground below both nRF52833 and nRF5340.

Thanks and best regards,

Jose P. Castro

RE: nRF5340 + nRF21540 connection

ketiljo — Tue, 24 Aug 2021 08:56:13 GMT

The regulator in the nRF53 can't supply the nRf21540 with enough current so you will need a separate regulator for the FEM in this case Also, the nRF82833 isn't designed to supply anything from the VDD net.

It's preferred to have ground plane as the next layer under the radio.

RE: nRF5340 + nRF21540 connection

Jose Pablo Castro Valverde — Mon, 23 Aug 2021 18:05:13 GMT

HI Ketil,

I got another question.

If I understand it right the power supply configuration for High voltage mode with USB(VDDH=VBUS) in circuit configuration no. 4:

and the datasheet says:

so, with this configuration VDD is a power source itself.

Can the nRF21540 VDD be connected to nRF5340 VDD in this configuration?

Same question for nRF82833 with configuration 1 for QDAA QFN40

And another question.

In a 4 layer stack-up, if I used one inner layer for power signals:

Is there any problem having VDD below the IC (both nRF52833 and nRF5340), or should I keep that area as GND?

The idea is to have signals only on the outer layers and GND and Powers in inner layers.

Thanks and Best Regards,

Jose Pablo Castro,

RE: nRF5340 + nRF21540 connection

ketiljo — Mon, 23 Aug 2021 10:50:47 GMT

You can do it like this, no problem. The lines are really too short to give you problems with the impedance. Just place the component as compact as you can and you'll fine.

cheers,

Ketil

RE: nRF5340 + nRF21540 connection

Jose Pablo Castro Valverde — Sat, 21 Aug 2021 21:32:40 GMT

Hi ketijo,

If I understand you correctly, there's no need to add or remove any component (Capacitance or Inductance).
Am I right?

I got another question regard to PCB board.

I am placing all components as close as possible, including the SMA Connector like this:

Between nRF52833 and nRF21540:

3D View (Kicad Nightly)

And between nRF21540 and SMA Connector:

3D View:

The stack-up is this:

And the width calculation for 50 Ohms is this:

Is this components placement and distance correct or should I increase the distance between components?

I am using the exact width of 0.355473 mm except between nRF52833 pin 24 (ANT) and C3 (The actual size is 0.3 mm)

as far as I understand the width is ok for 50 Ohms but I have my doubts especially if there could be any problem between C3 and pin 24 of nRF53833.

Any suggestion or recommendation?

Thanks and Best Regards,

José P. Castro

RE: nRF5340 + nRF21540 connection

ketiljo — Fri, 20 Aug 2021 10:08:46 GMT

Hi Jose

All the components shown on the nRF5233 and nRF21540 schematics are mandatory. Any antenna matching components comes in addition to L6, C28 and C30.