Dual-rail supervisor in a five-pin SOT-23
The MAX6420UK16+T: One channel has a fixed 1.575V threshold — sized for a 1.8V rail — while the second is adjustable via an external resistor divider, letting you set the trip point for a 2.5V, 3.3V, or any other rail the system carries. The open-drain output lets multiple supervisors share a common pull-up and reset line, so a board with separate 1.8V and 3.3V domains can OR their reset signals into one processor input without extra logic.
Threshold selection and reset timing
The fixed threshold of 1.575V monitors a 1.8V rail with typical margin — if the rail droops below 1.575V, the reset asserts. The adjustable channel uses an external resistor divider from the monitored rail to the ADJ pin; the internal reference is 0.6V, so the trip point is set by the ratio (R1+R2)/R2 * 0.6V. Reset timeout is adjustable/selectable via an external capacitor on the CT pin. Without a capacitor the timeout defaults to a minimum delay; adding capacitance extends the reset pulse width to let the rails stabilize before the processor starts. This is the same approach used in the MAX6421/MAX6422 family — the pinout and programming method carry across.
Temperature grade and board integration
No MSL rating is listed in the spec, but SOT-23-5 packages typically carry MSL-1 (unlimited floor life) unless otherwise noted on the reel label.
Active lifecycle — sourcing posture
The adjustable second channel gives flexibility across multiple board variants without changing the IC.