Current Limits

Blade2021
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Joined: Thu May 24, 2018 11:45 am

Current Limits

Postby Blade2021 » Thu May 24, 2018 11:48 am

Hi, I am having trouble finding out how much current the ESP32 output pins can provide and also how much current the whole package can handle at once.

Thanks,
- Matt

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kolban
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Joined: Mon Nov 16, 2015 4:43 pm
Location: Texas, USA

Re: Current Limits

Postby kolban » Fri May 25, 2018 4:11 pm

Looking at the ESP32 data sheet, it seems that the output current (source) on a GPIO should typically be about 40ma.

See:

https://www.espressif.com/sites/default ... eet_en.pdf
Free book on ESP32 available here: https://leanpub.com/kolban-ESP32

WiFive
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Joined: Tue Dec 01, 2015 7:35 am

Re: Current Limits

Postby WiFive » Fri May 25, 2018 11:45 pm

No it is 12mA. 40mA is for logic signals with capacitive loads.

ESP_Sprite
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Re: Current Limits

Postby ESP_Sprite » Sat May 26, 2018 3:40 am

Actually, no. There was some fuzz about the output current handling capacity for a while, but as far as I know, the 40mA number is correct: the 12mA number we used initially was a holdover from the ESP8266, but for the ESP32 we improved the IO-pads, so they can handle a larger current now.

mikemoy
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Joined: Fri Jan 12, 2018 9:10 pm

Re: Current Limits

Postby mikemoy » Sat May 26, 2018 3:49 am

40ma, is very high for an I/O pin. The data sheet does not specify what the total current capacity is. In other words, How may pins sourcing @ 40ma before you exceeded the current for the Vin pin.

WiFive
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Re: Current Limits

Postby WiFive » Sat May 26, 2018 5:26 am

ESP_Sprite wrote:Actually, no. There was some fuzz about the output current handling capacity for a while, but as far as I know, the 40mA number is correct: the 12mA number we used initially was a holdover from the ESP8266, but for the ESP32 we improved the IO-pads, so they can handle a larger current now.
:lol: esp32 keeps us guessing. Do you have to Max out the drive strength setting to get there and what is the max current per domain? And what about rtc I/o mode?

Archibald
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Re: Current Limits

Postby Archibald » Sat May 26, 2018 6:18 am

Neither 40mA nor 12mA applies to DAC outputs.

ESP_Sprite
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Re: Current Limits

Postby ESP_Sprite » Sun May 27, 2018 1:58 am

WiFive wrote: :lol: esp32 keeps us guessing. Do you have to Max out the drive strength setting to get there and what is the max current per domain? And what about rtc I/o mode?
Yes, as the datasheet specifies, this is at max drive strength. RTC I/O is the same, I presume. We indeed also need to specify the current per domain (because as is, the datasheet has nothing indicating it's a bad thing to pull 40mA out of all I/O pins, generating 5W of heat in the poor ESP32) but we need to do more investigation on that first.

Archibald
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Joined: Mon Mar 05, 2018 12:44 am

Re: Current Limits

Postby Archibald » Wed May 30, 2018 11:15 am

Below shows results of measurement of output voltage v. current for drive strength capabilities 0, 1, 2 and 3 (2 is the default).
VIgraph.png
VIgraph.png (56.2 KiB) Viewed 11962 times
The measurements were made with the following resistances: infinite, 2kΩ, 1kΩ, 470Ω, 220Ω, 150Ω, 100Ω, 47Ω and 0Ω. But for strengths 2 and 3 the minimum resistance was 100Ω.

By measuring into a capacitor, I can confirm that the source and sink current limits for drive strength 2 are about 40mA and for drive strength 3 they are about 80mA. Actually source current limits are a little higher than the sink current limits.

The drive capabilities of the digital-to-analogue converters are very different.

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