I am trying to use an SI7012 I2C sensor in a low power pro mini based sensor node. I am running into troubles trying to power the SI 7021 from a pro mini's digital pin (to save power while sleeping).
If I power the SI7021 from Vcc, the max current I measure is 1.09 mA; the datasheet states 4mA max during startup. And yet I fried two pins on the pro mini (#5 & #6) trying to use them to power the sensor; by that I mean that if I run a dummy sketch that sets pins 5 to 9 to output high, all pins are at 3.3V except the 2 ones I have used to power the sensor which are at 1.41V only.
I will write down the schematics, but as a general question is there any safety measures to take when powering a sensor directly from a digital pin? I could use a transistor of course, but a) I'd rather understand why I should and b) if the setup kills digital pins I guess it may kill the transistor just the same?