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. Reset timeout is a minimum of 1ms after all monitored voltages recover, which gives the system clock and core logic time to stabilize before the processor starts executing code.
What the ratings mean for your BOM
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.
Lifecycle and sourcing
No LTB risk for ongoing designs.