Two-voltage supervisor in a four-pin SC-70
The MAX6387XS22D3+ is a power-supply monitor that tracks two independent voltage rails and asserts a single active-low reset output when either falls below its threshold. One channel has a fixed 2.19 V threshold; the second is adjustable via an external resistor divider, so the same part covers a 3.3 V main rail and a 1.8 V or 1.2 V core rail with one resistor.
Reset timing and temperature range
Reset timeout is a minimum of 140 ms — long enough to let the downstream rails stabilise after a brown-out or power-up, but short enough that a 200 ms power-cycle resets the system cleanly.