ESP32-U4DWH - analog power supply design when not using WiFi

[nullbert]

We are using the ESP32-U4DWH chip without the WiFi features (WiFi will not be used at all).

The hardware design guidelines discusses the design of the analog power supply, including capacitors and the LC filter circuit for pins 1,3,4, 43 and 46.

How should I design the analog supply if WiFi will not be used? Should I just connect these pins to 3.3v without decoupling capacitors?

Also, how should I connect LNA_IN (pin2) - should I leave it open, or connect it to ground?

Thanks in advance.

[ESP_Sprite]

That is a good question. I've asked the documentation team if they can find the answers and amend it to the hardware design guidelines.

[nullbert]

Thank you! Hopefully we can avoid the decoupling capacitors to save board space.

[nullbert]

While we're at it, there's a recommended 499R resistor on U0TXD and a possible resistor on the Crystal XIN.

These are *only* to mitigate RF issues, correct? So if we're not using the RF side, we can omit these parts?

Thank you again,

[nullbert]

Hi, any word on this topic? We're waiting to order some prototype boards.

Thanks again for your help!

[ESP_Sprite]

Sorry, nothing yet, I think our hardware team has a bit of a backlog given the recent lockdown in Shanghai. If you need to make a proto, maybe you can put the footprints for the RF components on there but mark them as no-stuff and/or use zero-ohm resistors to bypass them until we have an answer for you?

[nullbert]

No problem, thanks for the reply. I'm making just a simplified version of it with 0.1uF capacitors and tying to 3.3v.

Two more questions:

* For the RC network on CAP2 on Pin 47 - if we don't care about power consumption for sleep mode, we can leave Pin 47 disconnected, right?

* For VDD_SDIO - as I understand, 3.3v mode is selected for the ESP32-U4DWH. This is provided within the ESP32, and does not need to be tied to 3.3v externally. In other words, only the 1uF capacitor needs to be attached to this line?

Thanks again for your help!

[ESP_Sprite]

* For the RC network on CAP2 on Pin 47 - if we don't care about power consumption for sleep mode, we can leave Pin 47 disconnected, right?

That is what the hardware design guidelines state, yes.

* For VDD_SDIO - as I understand, 3.3v mode is selected for the ESP32-U4DWH. This is provided within the ESP32, and does not need to be tied to 3.3v externally. In other words, only the 1uF capacitor needs to be attached to this line?

That seems correct.

[nullbert]

Thank you again for your help.

Espressif does a great job supporting their user community - other companies should take note of this.

[NuttyMonk]

Hi Nullbert,

i've just registered on this forum as i was coming to look for info to design a barebones ESP32-U4DWH project which doesn't use wifi/bluetooth and have found that you are doing the same thing. This is my first attempt at designing a PCB for a microcontroller and was hoping you could share your schematic (if it isn't covered by intellectual property) so i can get an idea for how it should be done.

I've been over quite a few schematics for the ESP32 but a lot of the components seem like they would be surplus to my requirements and i'm not sure which ones i can remove when i'm not using wifi and bluetooth.

I'm planning on having the USB connection and USB to Serial IC on a separate board so the final microcontroller PCB is as small as possible.

Cheers

NM