4.38V threshold — this one is for 5V rails
Its 4.38V threshold tells you this part monitors a 5V supply rail — it holds the reset output low until the supply comes up and stays above that threshold, then releases after the 120ms timeout.
Active-low push-pull output — no external pull-up needed
The reset output is active low with a push-pull, totem-pole stage. The 120ms minimum reset timeout gives the processor time to stabilize its oscillator and power rails before the reset is released.
Industrial temp in a 1x1mm package
The 4-X2SON package measures 1x1mm, so the PCB footprint is minimal. The exposed pad underneath needs a thermal via or a solid copper pour to the ground plane to keep junction temperature in check, especially if the ambient runs toward the top end.