2.64V threshold — the reset decision for 3.3V rails
That 2.64V threshold is the undervoltage trip point for a 3.3V rail — it sits well below the nominal 3.3V but above the minimum operating voltage of most 3.3V logic, so the processor gets a clean reset before the supply collapses enough to cause erratic behavior. The active-low output is the standard polarity for most MCU reset pins.
120ms reset timeout — timing the startup sequence
For a typical MCU with a 10ms to 50ms power-on ramp, this 120ms window provides enough margin that the reset de-asserts only after the supply is fully settled. The SOT-23-3 package keeps the footprint small, but the 0.95mm pitch means the PCB layout should follow the recommended land pattern for reliable solder joint formation during reflow.