What matching components should be used for the 5x5 QFN package?

rezarethink
Posts: 16
Joined: Fri Mar 24, 2017 4:15 am

What matching components should be used for the 5x5 QFN package?

Postby rezarethink » Thu Nov 02, 2017 5:01 pm

According to the datasheet, the smaller 5x5 QFN (ESP32-D2WD) part the output impedance is 35+j10 which is different than the larger 6x6 package. What matching components would be recommended that part vs the old part (which has a different output impedance)?

Also, I noticed that there are no matching components on the sparkfun esp32 board but it works fine. Why is that?

Thanks,
Reza

Franco
Posts: 53
Joined: Thu Dec 10, 2015 1:11 pm

Re: What matching components should be used for the 5x5 QFN package?

Postby Franco » Fri Nov 03, 2017 5:17 pm

Hi Reza, in the Sparkfun esp-32-thing schematic, I can see the matching circuit. https://cdn.sparkfun.com/assets/learn_t ... ematic.pdf
As far as the ESP32-D0WD you can use this circuit.
ESP32-D0WD.png
ESP32-D0WD.png (13.42 KiB) Viewed 4285 times
Let us know.

Lucas.Hutchinson
Posts: 79
Joined: Tue Apr 26, 2016 5:10 am

Re: What matching components should be used for the 5x5 QFN package?

Postby Lucas.Hutchinson » Sun Nov 05, 2017 8:35 pm

You should use a PI matching network (like that shown in the post above).

However please bare in mind that you will probably have to tune this network by altering the values of the conductors and capacitors depending on your circuit layout and antenna choice.

rezarethink
Posts: 16
Joined: Fri Mar 24, 2017 4:15 am

Re: What matching components should be used for the 5x5 QFN package?

Postby rezarethink » Mon Nov 27, 2017 10:22 pm

Although the sparkfun schematic might have those components in it, they only populate a small cap on the PCB, which is strange. Also, the sparkfun uses the 6x6 package and we use the 5x5 which has a different rated output impedance. There are references for the components used to match the 6x6 but nothing for the 5x5.

My main question is - what's a good starting point for matching components for the 5x5mm package?

-thanks in advance-

Franco
Posts: 53
Joined: Thu Dec 10, 2015 1:11 pm

Re: What matching components should be used for the 5x5 QFN package?

Postby Franco » Tue Nov 28, 2017 9:31 am

Hi Reza, the schematic I had posted before was from an early version of ESP-WROOM-32U. The datasheet http://espressif.com/sites/default/file ... eet_en.pdf has just been published and you can check the final schematic on page 15
[img]
ESP-WROOM-32U Pi filter.png
ESP-WROOM-32U Pi filter.png (81.33 KiB) Viewed 4145 times
[/img]
I hope this helps.

WiFive
Posts: 2952
Joined: Tue Dec 01, 2015 7:35 am

Re: What matching components should be used for the 5x5 QFN package?

Postby WiFive » Tue Nov 28, 2017 10:46 am

So wroom32 is switching from tapped capacitor matching to pi matching?

Franco
Posts: 53
Joined: Thu Dec 10, 2015 1:11 pm

Re: What matching components should be used for the 5x5 QFN package?

Postby Franco » Tue Nov 28, 2017 10:55 am

I checked the ESP-WROOM-32 (with PCB antenna) and the schematics on page 17 shows a similar Pi matching circuit.

WiFive
Posts: 2952
Joined: Tue Dec 01, 2015 7:35 am

Re: What matching components should be used for the 5x5 QFN package?

Postby WiFive » Tue Nov 28, 2017 12:12 pm

WROOM-32 has tapped capacitor matching circuit, so does WROVER.

WROOM-32D/U has pi circuit.

Interested to know reasons and effects.

Franco
Posts: 53
Joined: Thu Dec 10, 2015 1:11 pm

Re: What matching components should be used for the 5x5 QFN package?

Postby Franco » Tue Nov 28, 2017 4:22 pm

On this document it is stated "feature optimized antenna and RF performance" https://www.linkedin.com/feed/update/ur ... 1742822400

WiFive
Posts: 2952
Joined: Tue Dec 01, 2015 7:35 am

Re: What matching components should be used for the 5x5 QFN package?

Postby WiFive » Tue Nov 28, 2017 11:05 pm

That is interesting so will there be an update to wrover modules too?

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