What this comparator is and where it fits
The Texas Instruments LMC7221BIM is a single-channel, general-purpose comparator with an open-drain output stage. It operates from a single 2.7 V to 15 V supply or a dual ±1.35 V to ±7.5 V rail.
10 µs propagation delay — timing budget for the loop
The 10 µs max propagation delay is the time from when the input crosses the threshold to when the output switches. Budget the max for a robust design.
14 µA quiescent current — power budget for always-on sense
The maximum quiescent current draw is 14 µA. That's low enough to leave the comparator powered continuously in a battery-operated sensor node without draining the cell overnight. Compare that to older bipolar comparators that pull milliamps — this part saves the design a load-switch or a duty-cycling scheme. The open-drain output also draws no supply current when the output is high (the pull-up resistor carries the load), so the average power stays close to the quiescent figure.
Open-drain output — pull-up resistor required
The output is open-drain, rated to sink 30 mA typical. You must add an external pull-up resistor to the voltage you want the logic high to be.
Supply range and input offset — what to watch
The supply range is 2.7 V to 15 V single, or ±1.35 V to ±7.5 V dual. The maximum input offset voltage is 15 mV at 5 V.