I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go high when the current through the resistor exceeds a predefined value (of let's say 200mA).
This is to detect when a phone is actually pulling power from a +5V source. The circuit below illustrates my intent, by I feel that it is missing something, mainly that the comparator may not reset when the voltage across the sense resistor reaches zero. I'm not aiming for precision, but rather a rough "there is current" and "there is no current" type of circuit.