The MAX921ESA+T from Maxim Integrated is a single comparator with an integrated voltage reference, combining threshold detection and a precision 1.182V reference in one 8-SOIC package. It is designed for battery-powered threshold monitoring, undervoltage/overvoltage detection, and window comparators where every microamp counts. The 5µA max quiescent current makes it a strong fit for always-on sensor monitors, portable instrumentation, and industrial control loops that must stay alive on a coin cell or energy-harvesting supply. The 2.5V to 11V single-supply range (or ±1.25V to ±5.5V dual) covers common 3.3V and 5V rails with headroom for 12V industrial buses.
Industrial temperature range and environment
The 80dB CMRR and PSRR keep threshold accuracy stable across supply droops and common-mode shifts common in noisy industrial backplanes.
Output drive and response time
The 12µs max propagation delay is adequate for DC threshold and low-frequency monitoring; for high-speed PWM or zero-crossing detection, a faster comparator family would be needed.