Minimum supply voltage?

jmattsson
Posts: 31
Joined: Fri Jun 03, 2016 5:37 am

Minimum supply voltage?

Postby jmattsson » Wed Dec 21, 2016 5:56 am

We would like to run ESP32 modules on a 2.4-2.7V supply.

The ESP32 data sheet's pin list mentions that the chip itself can work down to 2.3V, the Espressif website claims 2.2V in the chip overview, and a post by John Lee here earlier suggested it was actually down to 2.0V. However, the data sheet's table 8 in section 5.2 specifies a minimum of 2.8V for "V_BAT".

However, that is the only mention of "V_BAT" or even the word "Battery" in the whole spec sheet. So we are not sure what it refers to. Is it the input for the internal VDD_SDIO LDO? If so, is it saying that the dropout on the LDO is 1V, so a minimum of 2.8V needs to be supplied for it to provide 1.8V to the flash?

What it comes down to is simply: Given an ESP32 module with a 1.8V flash chip, what's the lowest supply voltage for which the module will work?

jmattsson
Posts: 31
Joined: Fri Jun 03, 2016 5:37 am

Re: Minimum supply voltage?

Postby jmattsson » Tue Jan 03, 2017 2:14 am

Anyone? Bueller?

electronicsguy
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Re: Minimum supply voltage?

Postby electronicsguy » Mon Jun 26, 2017 3:02 pm

Did you try out various voltages and get an answer for this?

jmattsson
Posts: 31
Joined: Fri Jun 03, 2016 5:37 am

Re: Minimum supply voltage?

Postby jmattsson » Tue Jun 27, 2017 1:21 am

No, it's not something we'd be comfortable making assumptions on based on tests across a small sample. We ended up not using the ESP32 in the end.

ESP_Sprite
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Re: Minimum supply voltage?

Postby ESP_Sprite » Tue Jun 27, 2017 2:20 am

FWIW, the V_BAT spec is missing in the current data sheet, so I think it may have been a holdover from the ESP31 days. As far as I know, 2.3V is the actual minimum, although I wouldn't be surprised if there's a 0.3V safety margin and the ESP32 will work on 2.0V in normal environmental circumstances as well. (Do mind that the attached flash chip is also important: its specs usually are more narrow than that of the ESP32.)

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