ESP32 Forum

Hi,

Can someone please explain why ESP32-MINI-1 has operating voltage from 3.0 to 3.6V when ESP32-U4WDH (the MCU this module is based on) allows voltages from 2.3V? The MINI-1 has flash integrated in the chip so I don't understand which component inside the module limits the lower end to 3.0V?

ESP32-MINI-1 DS: https://www.espressif.com/sites/default ... eet_en.pdf
ESP32-U4WDH DS: https://www.espressif.com/sites/default ... eet_en.pdf

The integrated flash chip has a smaller voltage range than the ESP, hence the limit.

You mean flash integrated inside the ESP32-U4WDH chip has minimum operating voltage of 3V?
This module has flash integrated inside the MCU, it's not a separate flash chip like in WROOMs, WROVERs and others.
And ESP DS says it works from 2.3V, hence the reason for my question.

esp_zag0 wrote: ↑

Mon Feb 08, 2021 12:15 am

You mean flash integrated inside the ESP32-U4WDH chip has minimum operating voltage of 3V?
This module has flash integrated inside the MCU, it's not a separate flash chip like in WROOMs, WROVERs and others.
And ESP DS says it works from 2.3V, hence the reason for my question.

The flash is not integrated in the MCU (as in: the silicon die the MCU is located on), it's integrated in the package (as in: the black square with pads on the underside you actually solder to your PCB). It still is a separate die (physically sitting on top of the ESP32 die, connected with bond wires) and as such still has separate specs. Go read out the manufacturer ID of the flash if you don't believe me, it'll probably say something like Winbond or GD, I can't exactly remember whose dies we use for that.

Got it, thanks.

It's a bit misleading though, isn't it? If I'm about to buy ESP32-U4WDH (the chip, not the module) I'll read the DS and see 2.3V as minimum. There's no information in there saying one part of that "black square" works from 2.3V and another from 3V

PS. Why are you not using some other die for flash so it doesn't limit the entire product?

I have a prototype using ESP32-U4WDH designed for 3.3v but I tested just now and it boots at 2.7v

esp_zag0 wrote: ↑

Mon Feb 08, 2021 11:01 am

Got it, thanks.

It's a bit misleading though, isn't it? If I'm about to buy ESP32-U4WDH (the chip, not the module) I'll read the DS and see 2.3V as minimum. There's no information in there saying one part of that "black square" works from 2.3V and another from 3V

That's a good point, I'll see if I can poke the documentation team for that. Perhaps I'm wrong in my assessment it's the flash that it's the issue, but as there aren't too many other things in there, I don't know what else may set the temperature limit.

bryanergy wrote: ↑

Tue Feb 09, 2021 12:35 am

I have a prototype using ESP32-U4WDH designed for 3.3v but I tested just now and it boots at 2.7v

Do you have a chip prototype or a module prototype (MINI-1)?
Did you test lower, down to 2.3V?

Hi esp_zag0,

I do not have MINI1 exactly.

1. I have modified SOLO-1 DevKits with U4WDH installed, where the S0WDs used to be, Wi-Fi and all. These operate similar to SOLO-1. on board 3.3 v. How different is this from MINI1? (I have S2-MINI1 but not the original MINI1. I understand S2 uses a later processor, but also less RAM)

2. I concluded to expect U4WDH to work with Wi-Fi in my prototypes. My latest attempt boots equally well on 2.7v as on 3.3v. On these prototypes, the serial converter is also operating at the same VDD3p3. The USB VBUS is not driving on board power. I am seeing only partial operation of Wi-Fi, regardless 3.3v or any lower voltage.

Can you suggest the next steps to enable Wi-Fi as seen in 19303? In that case I'll trade some tech time to revise both my SOLO-1 and modified SOLO-1 operating on lower voltages (I'd have to remove LDO and whatever else to isolate the VBUS from the SOLO-1 board). Please see https://www.esp32.com/viewtopic.php?f=12&t=19303

Sorry, it took a while with Chinese new year coming inbetween, but I got a reply from my colleagues:

Yes, you are right. ESP32-MINI-1's operating voltage is limited by its flash in the SoC, so it's 3.0 ~ 3.6 V, not 2.3 ~ 3.6 V. The ESP32 Datasheet is not updated yet.

We will update the ESP32 datasheet to reflect this.

(Also note that your module may or may not boot successfully on a voltage outside of this range, like the 2.7V mentioned before. We cannot guarantee that the module will work correctly in every circumstance if you stray outside of those specs, though.)