ESP32 Forum

Hi,

I'm building a schematic using the ESP32-D2WD.

In the datasheet, it says to "tie" VDD-SDIO to VDD3P3_RTC to disable the LDO on VDD-SDIO.

For the ESP32-D2WD with integrated flash, is VDD-SDIO used to power the flash internally. Should I just leave VDD-SDIO floating on my layout?

If it is not used, can I just tie VDD-SDIO without any capacitors to VDD3P3_RTC to disable the LDO?

Of course if the LDO is not being used, I want to disable it to save current consumption.

tpayne03 wrote:For the ESP32-D2WD with integrated flash, is VDD-SDIO used to power the flash internally.

Yes

If it is not used, can I just tie VDD-SDIO without any capacitors to VDD3P3_RTC to disable the LDO?

But that would also connect flash power rail to 3.3V supply, while the flash is a 1.8V part. Not sure how that would reduce power supply?

Okay, I'm confused now. I'm just going off what the datasheet says... I'm using the D2WD, so I was going to leave VDD_SDIO floating.

I understand VDD_SDIO is a 1.8V power rail, right?

Is VDD3P3_RTC a power rail, or a power input for the RTC?

The datasheet says to tie VDD_SDIO to VDD3P3_RTC to turn off the LDO (I was thinking it is the LDO in the die supply VDD_SDIO)...

This is relevant now, because I'm trying to figure out if I need to power VDD3P3_RTC or not, for my layout with a 32KHz crystal.

I was looking at the Sparkfun ESP32 schematic. (Been a very good reference).

They supply a 3.3V power source, and use a 0.1uF decoupling capacitor to VDD3P3_RTC.

Seems like VDD3P3_RTC is a 3.3V input to power the RTC. Makes sense.

I'm not really sure, what the datasheet means when it says to tie VDD_SDIO to disable the LDO.

I see some things where you can adjust the VDD_SDIO voltage for an external flash by changing some registers. Not sure how it works, not really relevant to our design using the ESP32-D2WD.

You may want to check the datasheet, and clarify. (Sounds like fun -- NOT).

For the ESP32-D2WD, off the cuff it seems like you are not using VDD_SDIO, so you would want to disable the LDO and eliminate any quiescent current draw with that LDO.

Screenshot:

Now I am making myself more paranoid. If I supply 3.3V to VDD3P3_RTC, will that cause an error with the internal flash?

There is another sentence that "VDD_SIO is 1.8V OR THE SAME VOLTAGE as VDD3PE_RTC" -- is that defined by a register or does VDD_SDIO
take the voltage of VDD3PE_RTC?

Is the internal flash 1.8V or 3.3V in any case....

1.8v for d2wd. Voltage is set by gpio 12 strapping pin. D2wd flash is still "external flash" just wired up inside the package so you shouldn't treat it much differently.

Thanks. I see MTDI has an internal pull down, which means VDD_SDIO is at 3.3V.

Does that mean for the ESP32-DWD, I need a pull up on MTDI so the IC sets the LDO for 1.8V?

Yes it is recommended even if you set the efuse to force 1.8