1.434 V threshold — fit for a 1.8 V rail
That threshold is 0.366 V below a nominal 1.8 V supply, so the reset asserts when the rail droops below 1.434 V — typical for supervising 1.8 V logic or I/O voltages. The active-low, open-drain output pulls low during reset and releases when the supply rises above the threshold plus hysteresis, with a guaranteed minimum reset timeout of 65 ms to let the system power-up cleanly.
Open-drain output and the pull-up resistor
The open-drain output lets you wire-OR the reset signal with other supervisors or pull it to a different voltage level (e.g., 3.3 V) independent of the monitored rail.
The base product number TPS3103 covers several threshold options in the same SOT-23-6 footprint, so if the voltage requirement shifts, a pin-compatible variant is available without a board spin.