The Texas Instruments TPS3306-25DR is a multi-voltage supervisor designed to monitor two independent supply rails. It asserts a reset signal when either monitored voltage drops below its threshold — 2.25V for the 2.5V rail, 2.93V for the 3.3V rail — and holds reset for a minimum of 70ms after both rails return above threshold. The open-drain, active-low output lets you wire-OR this supervisor with other reset sources, and the 8-SOIC package fits a compact board footprint.
The 2.25V and 2.93V thresholds are set to monitor nominal 2.5V and 3.3V rails respectively, with roughly 10% undervoltage detection margin. This is the standard guard band for most logic families — if your 3.3V rail droops below 2.93V, the supervisor flags it before the downstream FPGA or MCU enters an undefined state. The 70ms minimum reset timeout gives the power supply and crystal oscillator time to stabilize after a brown-out or power-up event. Most ARM Cortex-M and FPGA devices require a reset pulse width of 1-10 ms, so the 70ms window provides comfortable margin across temperature and load transients. The pull-up voltage sets the logic-high level seen by the processor reset input — match it to the processor's Vih threshold.
This removes the obsolescence risk for production BOMs that will run for several years.