2.625V threshold — the rail it watches
The MAX6421US26+T is a single-channel voltage supervisor from Analog Devices, built for the simple reset/power-on reset job. Its 2.625V threshold sits right at the edge of a 2.5V rail's undervoltage limit or a 3.3V rail's brownout zone — you pick the capacitor to set the reset timeout. The active-low, push-pull output means no external pull-up resistor, which saves a component and a trace on a tight board. Rated across -40°C to 125°C, this part handles automotive under-hood or industrial motor-drive environments without a second temperature-grade variant.
Adjustable timeout — one cap sets the delay
Unlike fixed-timeout supervisors that lock you into a 100 ms or 200 ms window, the MAX6421US26+T lets you choose the reset release delay with a single external capacitor. That matters when your microcontroller needs extra time for the oscillator to stabilize or an external regulator to ramp. The trade-off: one more BOM line and a small PCB footprint for the cap. If your design already uses a fixed-timeout part and you want to standardize, the MAX6420US26+T is the fixed-delay sibling worth comparing.
Active lifecycle — no LTB surprise
Listed as Active with ROHS3 compliance, the MAX6421US26+T is not on any end-of-life watch. That means you can qualify it into a new production BOM without worrying about a last-time-buy window closing mid-program.
SOT-143-4 — small, surface-mount, field-swappable
The SOT-143-4 package (also listed as TO-253-4) is a common four-pin footprint for voltage supervisors. It is small enough for space-constrained designs but large enough to hand-solder with a fine tip if you are doing rework or field repair. No exposed pad, no thermal vias — just four pads and a clear orientation mark. If you are swapping this on site with a basic iron, the active-low output and push-pull stage mean you do not need to check for a missing pull-up resistor on the replacement board.