Two-rail supervisor for mixed-voltage boards
The TPS3306-25DG4 from Texas Instruments is a multi-voltage supervisor that monitors two independent supply rails, with reset thresholds set at 2.25 V and 2.93 V — a natural fit for systems running a 2.5 V core rail alongside a 3.3 V I/O rail. It asserts a reset output when either monitored voltage drops below its threshold, and holds reset active for a minimum of 70 ms after both rails recover, giving the downstream processor time to stabilize before release.
Open-drain output and wired-OR flexibility
The output is open-drain, active-low — this lets you wire-OR the reset signal with other supervisors or a manual reset button without adding external logic gates. A pull-up resistor to the I/O rail is required; the value sets the rise time on the reset line.