https://docs.pycom.io/.gitbook/assets/l01-pinout.pdf says: 3V3 pin: Supply with a stable 3V3 power source capable of delivering at least 650mA

@martinnn said in Protection circuit for Analog Pin: How exactly do you suppose this to function? This is what I put into a online simulator. If I change the impedance on the right then I can adjust the trim pot and it changes the working range. [image: 1551398013598-c8ac1f5a-9119-49ea-a614-6e56c948f1a1-image-resized.png] This is a digital input, not an analog one. Re-read what I wrote about input protection. How much current flows into the input? Draw a schematic including the input protection as in the article you are referring to (hint: Figure 6). Do you mean what you wrote when you said to use an input series resistor. Is the circuit above what you meant? EDIT: I have since found out that the impedance will be minimal. It is just the resistance of a short cable. So less than 1 ohm. Also this device will go into deep sleep in which case there will still be the analog but no power to the FiPy. Won't this then apply a voltage to VDD?

@curtis-hendrix I have no spec but I once tried to connect a small LCD display to that power pin. That was an instructive failiure. Even 400 mA is optimistic (may only be reachable at the limit of 5.5 V Gpy supply). You can safely use that 3.3 V pin to supply some I²C chips but nothing that needs power.

@jcaron Isn't this the opposite of what what stated here: Not completely the opposite, it's still more efficient to use a regulated 3.3V supply (low voltage forces the onboard regulator into bypass ECO mode) But it needs to be updated to reflect that 3.3V should be applied to the 5V/VIN pin. Is the Pysense/Pytrack sending power to the module via 5V Yes, all the various shields implementing deep sleep control the *py board's 5V rail