What this supervisor does on your board
The TPS3809J25DBVR is a single-channel voltage supervisor from Texas Instruments that monitors a 2.25V rail and asserts a reset signal when the supply drops below that threshold. The reset output is active-low push-pull, which means it drives the reset pin of an MCU or DSP directly without needing an external pull-up resistor.
Threshold voltage and reset timing — the selection anchors
The 2.25V threshold is the voltage at which the reset asserts — it must match the monitored rail's nominal voltage minus the regulator tolerance. For a 2.5V rail, this threshold sits about 10% below nominal, which is a common margin for detecting brownout conditions. The 120ms minimum reset timeout is the guaranteed hold time after the supply crosses the threshold; this is long enough for most MCU power-on-reset sequences but short enough to avoid delaying system startup. The push-pull output eliminates the external pull-up resistor needed with open-drain supervisors, saving one component per rail.
Temperature grade and package — fit for industrial boards
The SOT-23-3 package is a three-pin surface-mount footprint that fits into tight layouts. It is ROHS3 compliant.
How to order and sourcing posture
The base product number is TPS3809, and the full ordering code includes the voltage suffix and package variant. Sourcing is handled per RFQ — confirm the required quantity and preferred packaging, and we will provide a current price and lead-time quote.