Disable VDD_SDIO -- ESP32-D2WD

[tpayne03]

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.

[WiFive]

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

Yes

[ESP_igrr]

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?

[tpayne03]

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.

[tpayne03]

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.

[tpayne03]

Screenshot:

LDO_Disabled.jpg (80.57 KiB) Viewed 12855 times

[tpayne03]

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....

[WiFive]

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.

[tpayne03]

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?

[WiFive]

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