2.25V supervisor for a single supply rail
When the monitored supply drops below that threshold, the push-pull output asserts both active-high and active-low reset signals, holding them for a minimum of 140ms after the supply recovers.
Reset timeout and threshold — what they mean on the board
The 2.25V threshold is the trip point at which the reset asserts. For a 2.5V or 3.3V rail, this threshold sits low enough to catch a brownout before the downstream logic loses state, but high enough that the reset asserts before the supply falls below the minimum operating voltage of most 3.3V logic. A shorter timeout risks the CPU running before the clock is valid; a longer one delays the system start-up unnecessarily.