Voltage/current ratings on ESP32 pins

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Voltage/current ratings on ESP32 pins

Postby permal » Sun May 14, 2017 5:46 pm

I believe I've read through every document I can find, but nowhere have I seen information regarding voltage and current limits for the ESP32 pins in their different configurations (ADC, I/O etc). Is this information actually missing or have I just overlooked them?

If they indeed are there, would someone please point it out to me?

Thank you.

ESP_Sprite
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Re: Voltage/current ratings on ESP32 pins

Postby ESP_Sprite » Mon May 15, 2017 1:44 am

Does the datasheet not mention the pin I/O specifications? Modes don't really have anything to do with that, the pad drivers will be the same.

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Re: Voltage/current ratings on ESP32 pins

Postby permal » Mon May 15, 2017 8:56 pm

Well, perhaps it does. Section 5 of https://espressif.com/sites/default/fil ... eet_en.pdf specifies the electrical characteristics, and 5.1, table 7 might be what I want. However, the absolut maximum rating for input high is given as 3.3V. Does that mean that the ESP32 doesn't have any internal clamping/protection? Usually a uC can handle a few 100mV above its Vcc.

Another thing I can't find is the ADC ranges, i.e. do they support rail-to-rail measurement?

I'm attempting to design a small I/O board with digital & analog inputs and some digital outputs based on Sparkfuns ESP32Thing. The digital inputs are no problem since they can be electrically separated using opto-couplers, but the analog inputs are trickier since I need to handle voltage inputs 5-48V. An adjustable voltage divider is a good start, but getting the inside clamping to 3.3V in order to protect the ESP32 is causing some issues.

ESP_Sprite
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Re: Voltage/current ratings on ESP32 pins

Postby ESP_Sprite » Tue May 16, 2017 1:24 am

The ESP32 does actually have an internal snapback circuit that protects it from overvoltage; in theory you should be able to feed it a fair amount of volts more. However it stresses the pad silicon (due to increased electron tunneling, iirc) and the long term effects aren't known so it's not in the datasheet.

The ADC can do rail-to-rail measurements; however be aware that they're not entirely linear and more so at the end of the voltage spectrum. We're working on characterizing this and will include code to normalize the readings in esp-idf as soon as that's done.

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Re: Voltage/current ratings on ESP32 pins

Postby permal » Tue May 16, 2017 6:49 pm

Ok, thanks. I believe I now know enough to go ahead with my design.

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