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What is the maximum input voltage on the Ai-Thinker ESP32-CAM?

I'm asking because the official docs specify a max input voltage of 5.25V, however it has an AMS1117 power regulator which has a maximum input voltage of 15V.

So I'm wondering what the highest voltage I can put into the 5V input safely?

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  • \$\begingroup\$ what do you mean by input voltage? ... which pin are you referring to? \$\endgroup\$
    – jsotola
    May 10, 2022 at 0:39
  • \$\begingroup\$ @jsotola When I say input voltage I am referring to the voltage from an external power source that is input into the circuit. I am also referring to the pin labeled "5V". \$\endgroup\$ May 10, 2022 at 0:55
  • \$\begingroup\$ The application of AMS depends on max temp rise not just V or I but 'C/W * VI drop \$\endgroup\$ May 10, 2022 at 2:32
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    \$\begingroup\$ it actually depends on the code, if you use wifi/bt, etc. if you don't use any high-drain features or you sleep most of the time, you can go a bit above 5.5v. It would be better though to put an lm7805 or a buck smps in front of it to deliver 5v to the module from a 9-24v supply. \$\endgroup\$
    – dandavis
    May 10, 2022 at 4:12

2 Answers 2

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I've been looking for a while now at the documentation/schematics for the ESP32-CAM module, the ESP32 module it is built around, and the ESP32 itself.

The power supply range is, as you've mentioned, specified to 4.75-5.25V, but I see no reason it wouldn't accept up to 15V since the 5V input pin is only connected to the 15V-tolerant AMS1117 (assuming only one of R1 and R2 are mounted on the ESP32-CAM module). As dandavis points out in the comments, the power dissipation is a reason, so it is best to stick to the maximum rating given by the ESP32-CAM module specifications.

However, the logic input pins seems to be (again, as far as I can tell) seems to be limited to 3.6V (or even 2.1V, depending on configuration). Page 45 of the ESP32 datasheet specifies the max input voltage to VDD+0.3V, where VDD is the IO-pins power domain. This power domain can be at 3.3V, or at 1.8V if the pin is in the VDD-SDIO domain, and this is configured to 1.8V.

ESP32 datasheet, page 45

I can't see any indication in any of this documentation that there is some level-shifting or other stuff going on to make the pins 5V-tolerant, let alone 15V.

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    \$\begingroup\$ "I see no reason it wouldn't accept up to 15V"; look at the dissipation in the datasheet and remember that the ESP32 can draw up to 150ma; 1.75W going into a tiny surface-mount regulator... \$\endgroup\$
    – dandavis
    May 10, 2022 at 20:41
  • \$\begingroup\$ @dandavis that is a very good point. I edited the answer to highlight this. \$\endgroup\$
    – sondre99v
    May 11, 2022 at 6:28
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As you wrote yourself, the maximum specified supply voltage is 5.25V and that is the value that is relevant for you. The fact that the converter can handle 15V does not mean it can handle the power dissipation in the specific application. The ESP-CAM (ESP32 + external RAM + camera) may require up to 500mA peak current. Even 200mA of average current would lead to 2.4W of power dissipated by the regulator itself. Adding the power dissipated by the ESP module, that's certainly too much for that small board to dissipate, according to table 1 of the AMS1117 datasheet, a 1000 mm^2 copper area still results in a thermal resistance of 60 °C/W.

The developers of the ESP-CAM are the ones who know the board's characteristics best and they have their reasons to rate the input accordingly.

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