Power ESP-01 (ESP8266) via Mega2560 R3

I am powering a Mega2560 with a 12V DC power supply through the onboard power jack of the Mega.

I've connected the Mega to a ESP8266 to get WiFi connectivity.

I understand that the 3.3V output on the Mega isn't powerful enough to drive the ESP8266.

Can I use the VIN pin of the Mega (which should provide the 12V from my DC power supply) connected to a BUCK converter stepping down to 3.3V?

the 3.3 V pin of Mega is good for the esp8266 in normal conditions (AP not too far)

I thought the 3.3v pin used the same rice-grain sized regulator as the Uno - the one I have in arms reach does, at least. Powering an ESP8266 with one of those can be hit or miss.

The buck converter solution is fine, assuming you aren't hoping to sleep it and run off batteries or something, but if you're using a Mega, you're not doing that anyway.

following is the ESP8266 measured current consumption. The killer is when the WiFi, it requires current. Remember the circuit design shows the 3.3V regulator being powered with the 5V regulator.
State Consumption
Power down 200 µA
Active, WiFi OFF 34 mA
WiFi ON 67 mA + 435 mA spikes
I would venture to say if you touched either regulator on the mega you would have some chard flesh. Best solution is use a separate power supply for the ESP8266 and be sure all grounds are connected. This came from Determining the ESP8266 power consumption - Ondrovo.com This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil

gilshultz:
I would venture to say if you touched either regulator on the mega you would have some chard flesh.

Charred? No. It might be uncomfortably hot, but they would either burn out or overheat and shut down before getting that hot.