Schematic review

RE: Schematic review

JONATHAN LL — Mon, 17 Oct 2022 08:55:47 GMT

Hi Tinashe,

So for the Crystals, we often recommend to ground even the NC pin, it is not necessary. Reason for this is that we have seen some cases where customers has mounted the crystals with a 180 degree rotation. And as far as i am aware we have not seen any down sides by grounding the NC pin.

But feel free to do as the datasheet recommend, as that is the actual recommendation of the components that you are using.

[quote user="tmarera"]Antenna matching is optional. The antenna input impedance is 50 ohm.[/quote]

It often says optional in the datasheets of these chip antennas, but more often then not there needs to be some tuning. This is due to the fact that there are other factors that is effecting the antenna, like the casing of the product and in what environment it is mounted.

I like to recommend a full Pi-network as close to the antenna as possible. And since you do in fact have a large hole right next to the antenna, probably for the mounting mechanism of the PCB, it can\will effect the antenna, so it is likely that some tuning is needed for optimal performance.

I also see that the files in the .tgz does not match the images you uploaded first, did you do some changes,what is the latest versions?

Adding some general comments on the layout here:

The ground area on the top layer around the antenna should ideally be a consecutive layer, so try to tie the two sections of top layer GND together.

There seems to be enough room to move the SoC and the components further in that would give you more room to have a consecutive plane around the antenna.

I am curious about the J1, how large is it an will it cover parts of the antenna or the transmission line? This could effect the impedance of the trace.

L1 and L2 should not be placed orienting the same way, the inductors have a chance of resonating so to minimize the risk one of the inductors should be rotated 90 degrees.

Regards,
Jonathan

RE: Schematic review

tmarera — Wed, 12 Oct 2022 17:05:19 GMT

Hi Kazi,

Thanks for the feedback.

Pin 4 is supposed to be floating.

Antenna matching is optional. The antenna input impedance is 50 ohm.

Thanks

RE: Schematic review

Kazi Afroza Sultana — Wed, 12 Oct 2022 13:17:54 GMT

Hello,

I have checked the design.

The pin 4 of the high frequency crystal is not grounded. You can see pin 4 is floating.

You do not have any antenna matching network in the design. Based on your antenna matching network would vary. You can look into these issues.

Thanks.

Kazi

RE: Schematic review

tmarera — Mon, 10 Oct 2022 16:57:52 GMT

You may you viewmate viewer, which is free to download to look at the ODB++ file in case your default viewer doesn't work

RE: Schematic review

tmarera — Mon, 10 Oct 2022 16:56:21 GMT

devzone.nordicsemi.com/.../6136.g651_2D00_02906_2D00_01_5F00_odbjob.tgz

RE: Schematic review

Kazi Afroza Sultana — Mon, 10 Oct 2022 08:03:43 GMT

Hello Tinashe,

Could you please send the Gerber file of your pcb design? That would be really great , currently I can not open the .brd file.

Thanks.

BR
Kazi

RE: Schematic review

tmarera — Thu, 06 Oct 2022 16:05:31 GMT

devzone.nordicsemi.com/.../0118.Nordic-review.zip

RE: Schematic review

Kazi Afroza Sultana — Thu, 06 Oct 2022 13:36:17 GMT

Hello Tinashe,

There is attaching image/video/file option from the insert menu. You can upload your zipped folder from there.

Thanks.

Kazi Afroza Sultana

RE: Schematic review

tmarera — Tue, 04 Oct 2022 21:38:03 GMT

Stack-up

Layout pictures:

top layer - Signal/Pwr

Second layer - Ground

Third layer - Ground

Fourth layer - Signal/Pwr

RE: Schematic review

tmarera — Tue, 04 Oct 2022 21:12:41 GMT

Hi Kazi,

Hope you are well,

I finished the layout for this design and I wanted to ask for some review help. What's the best way to share the stackup and .brd layout files. This portal is not allowing me to attach files.

Many thanks

Tinashe

RE: Schematic review

Kazi Afroza Sultana — Mon, 19 Sep 2022 10:08:37 GMT

Hello Tinashe,

We don't have impedance measurements of the ANT pin. After adding the radio matching network the impedance should be close to 50 ohm.

There are two previous case you can look at (+) Nordic DevZone (nordicsemi.com), (+) Nordic DevZone (nordicsemi.com).

Thanks.

Best Regards,

Kazi Afroza Sultana

RE: Schematic review

tmarera — Thu, 15 Sep 2022 21:40:15 GMT

Hello,

Thanks for the feedback. What is the output impedance of the ant pin at the broadcasting frequency 2.4GHz? The antenna that I have chosen have 50 ohm input impedance so if that matches with the output impedance for the ant pin I might not need the matching circuit.

Many thanks

Tinashe

RE: Schematic review

Kazi Afroza Sultana — Thu, 15 Sep 2022 12:48:00 GMT

Hello,

I have checked the schematic. There is not matching network for radio. You can look at our reference design to see the matching components for Radio.

The VSS pin is also not grounded through the capacitor C3 as like as reference design.

Here are the answers of your questions:

1. On the reference design you have a 10uH and a 15nH inductor in series for the DC/DC regulator filter. Is the 15nH inductor necessary?

The high frequency 15 nH inductor is used to filter high frequency noise from the DCDC converter that can affect the receiver. This is important to achieve the specified RX sensitivity.

2. I have used the following xtal crystals for the 32.768Hz and the 32MHz frequencies respectively: 9H03280012, and 8Q32070006. Will these work well for your chipset? Also recommended known ones you have used in the past if these don't work.

I am not able to find any datasheet that matches the two crystals that you have shared. Can you share the data sheet with me so that I can be sure that I am not reading the wrong documentation found? We have our crystal specifications here (https://infocenter.nordicsemi.com/topic/ps_nrf52810/clock.html?cp=4_5_0_4_3_3_1#unique_1332589092) and (https://infocenter.nordicsemi.com/topic/ps_nrf52810/clock.html?cp=4_5_0_4_3_3_3#unique_915206003) which you also can see to match your crystal specification.

3. I am using this chip antenna on the board, let me know if you foresee any issues with this: w3008

Yes, You can use chip antenna mounted on the board. Currently you have one shunt capacitor which is ok. It might be nice to add a full pi or T network for matching.

Thnaks.

Best Regards,

Kazi Afroza Sultana

RE: Schematic review

tmarera — Wed, 14 Sep 2022 21:43:05 GMT

devzone.nordicsemi.com/.../4810.gen2_5F00_force_5F00_sensing_5F00_rigid_5F00_board.pdf

RE: Schematic review

Kazi Afroza Sultana — Wed, 14 Sep 2022 09:30:07 GMT

Hello Tinashe,

Thanks for your queries. Could you please send the schematic design in pdf file? Now It's a bit difficult for me as value of the components are not visible clearly.

Best Regards,

Kazi Afroza Sultana