USB to 3.3 V

// 3.3 V from USB with a low dropout regulator.
//
// There is no microcontroller here. Press Run and the simulator solves the
// circuit.
//
// WHAT IT IS. A USB-C power breakout plugged into a computer, 5 V on VBUS,
// into an AP2112K-3.3: the regulator most ESP32 boards make their 3.3 V with.
// Its output lights a red LED through 330 ohms.
//
// THE NUMBERS. The readout under the regulator says 3.30 V. The LED takes
// about 5 mA, and the regulator's own bias is 55 uA, so the port gives about
// as much as the load and no more: a linear regulator's input current is its
// output current.
//
// WHY A LOW DROPOUT PART. The AP2112K needs only 250 mV across itself at its
// full 600 mA. Change the model to AMS1117-3.3 in the regulator's properties:
// it still makes 3.3 V from 5 V, but it needs about a volt, so from a 3.7 V
// LiPo it could not. Try it: swap the USB part for a battery, kind lipo1000,
// and compare the two models.
//
// THINGS TO TRY. Set the breakout's source to charger; nothing changes, since
// the load is far under even a computer port's half an amp. Then put a 4.7
// ohm resistor across VBUS and GND: an amp from a computer port is more than
// it gives, and VBUS falls.