Two-rail supervisor in a SOT-23-5
The MAX6306UK30D1+T is a multi-voltage supervisor from Analog Devices that monitors two supply rails and asserts an active-low reset when either falls below its threshold. One channel is fixed at 3V; the second channel is adjustable via external resistors, so you can set a custom trip point for a secondary rail like 1.8V or 2.5V. The open-drain output lets you wire-OR the reset signal with other supervisors or a manual reset button.
The 3V fixed threshold on channel 1 is a standard trip for 3.3V rails — it asserts reset when the supply drops below about 2.9V (typical), catching brownouts before the logic fails. The adjustable second channel lets you monitor a lower-voltage core rail (e.g., 1.2V or 1.8V) with a resistor divider. The 1ms minimum reset timeout is short enough that a brief glitch on the supply won't cause a full system restart, but long enough to cover the power-good settling time of most switching regulators. The open-drain output means you need a pull-up resistor to the supervisor's supply or to the monitored rail — choose a value that keeps the rise time within the processor's reset input spec.
No LTB risk for ongoing designs.