ESP32-POE-ISO ver. C ESP-EN Signal problem

Started by A2B, January 12, 2021, 07:42:08 pm

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A2B

Hello, I have a ESP32-POE-ISO version C, and when I power by USB the voltage level at pin ESP_EN is above 4 volts (4.2V aprox). When I power by PoE I don`t have this problem, the voltage level at pin ESP_EN is 3V3. Reviewing the schematic, the problem is when RTS# pin of U1 (USB to UART) is at high level, I have current between pin 2 and 3 of Q2 with a voltage drop around 0.5V. This is happening because U1 is powered by 5V. For example, I have checked in ESP32-POE version C and I don`t have this problem. This is because between version C and D of ESP32-POE you change the power supply of U1 from 3V3 to 5V. My question is: Can this be a problem for ESP_EN pin? What is the absolute maximum voltage range for this pin? Thank you

LubOlimex

It shouldn't be a problem, there is a resistor but the team is looking into it. At least we have encountered 0 issues so far. But we would definitely look into into it, we might place a diode like at the RX and TX lines in future.

The switch from 3.3V to 5V powering of CH340T was to minimize the power consumption when powered by battery.

Technical support and documentation manager at Olimex

A2B

Ok, thanks for the reply. I also think that it shouldn't be a problem because I have some boards working like this. My only concern is that the ESP_EN input will not tolerate a voltage value above 3V3 and could end up failing. Any news that you find on this, I would appreciate if you would comment on it here.