Single comparator with a built-in reference — what that buys you
The MAX921EPA+ is a single comparator from Maxim Integrated that packs its own voltage reference on-chip. That means you get a stable threshold without an external reference IC or resistor divider — one less component to source and place. The internal reference is trimmed, so the trip point holds across temperature and supply shifts. Quiescent current maxes out at 5 µA. The single supply range covers 2.5 V to 11 V, or split rails ±1.25 V to ±5.5 V.
The 12 µs max propagation delay sets the response speed for over-voltage or under-voltage detection. That is fine for line-frequency monitoring, battery charge termination, or slow sensor thresholds. It will not work for high-speed PWM current limiting or fast-switching power supply protection — those need a comparator in the sub-microsecond range. The 50 mV of built-in hysteresis cleans up the switching edge on a noisy rail and prevents chatter near the threshold.
Through-hole DIP — still the right call for lab, prototype, or high-reliability builds
The 8-pin DIP package (0.300" body, 7.62 mm pitch) is through-hole, not surface-mount. That makes it easy to hand-prototype, socket in a test fixture, or mount on a board that avoids SMD reflow for reliability reasons. The 8-PDIP supplier package code is the same footprint. Output is CMOS and TTL compatible, so it drives logic inputs directly without a pull-up resistor.
Lifecycle and compliance — no end-of-life surprises
Sourcing — available through independent distribution
Submit an RFQ for tube quantities as shipped from the factory.