ESP8685 LNA_IN Impedance

axe111
Posts: 2
Joined: Thu Dec 28, 2023 9:02 am

ESP8685 LNA_IN Impedance

Postby axe111 » Thu Dec 28, 2023 9:05 am

Hi there,

in the Datasheet of ESP8685 the impedance of LNA_IN pin is not listed.
In ESP32-C3 Datasheet also no value is given.

Please advise on which value to use for ESP8685H4 chip.

Thank you!

ESP_Minatel
Posts: 364
Joined: Mon Jan 04, 2021 2:06 pm

Re: ESP8685 LNA_IN Impedance

Postby ESP_Minatel » Thu Dec 28, 2023 11:05 am

Hi,

Please take a look at the ESP32-C3 Hardware Design Guidelines page.
The RF trace should have a 50 Ω characteristic impedance.

axe111
Posts: 2
Joined: Thu Dec 28, 2023 9:02 am

Re: ESP8685 LNA_IN Impedance

Postby axe111 » Thu Dec 28, 2023 12:30 pm

Hi,

thank you. The Trace to the Antenna should be 50Ω single ended impedance.
Matching circuit is intended for matching LNA_IN pins output impedance to the trace and later to the antenna.

However Hardware design guide and Datasheet do not mention the ouput impedance of LNA_IN pin, so this is what i am looking for.

In addition I think there is an error in https://docs.espressif.com/projects/esp ... tub-layout. As stated the stub from first C should be connected to L3 (which is power according to stackup) and I do think this should be L2 which is supposed to be GND.

Is the output impedance the same as ESP32-C3? I found here https://esp32.com/viewtopic.php?t=21649 that it should be: (30 ~ 40) ±10 jΩ
Or is the package already matched internally to 50Ω?

ESP_Minatel
Posts: 364
Joined: Mon Jan 04, 2021 2:06 pm

Re: ESP8685 LNA_IN Impedance

Postby ESP_Minatel » Fri Dec 29, 2023 11:44 am

Regarding the POWER plane layer question:

https://docs.espressif.com/projects/esp ... #rf-tuning
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