What this supervisor does that a simple RC reset doesn't
The STM6315RDW13F is a single-channel voltage supervisor from STMicroelectronics — a Simple Reset/Power-On Reset type that holds the reset line low when the monitored supply drops below 2.63V and releases it after a 112ms minimum timeout once the rail recovers. The open-drain output lets you wire-OR it with other reset sources, and the active-low polarity matches the majority of MCU reset inputs.
2.63V threshold — why that number matters
The 2.63V threshold sits just below the typical 3.3V ±10% supply, so it triggers before the logic rails fall out of spec but doesn't nuisance-trip on normal ripple. For a 3.3V system, this means the supervisor asserts reset when the rail dips to roughly 80% of nominal — early enough that the MCU's internal POR hasn't already lost state, but not so early that every capacitor charge cycle causes a reset. If your design runs from a 5V or 1.8V rail, this threshold won't work; you'd need a different voltage option in the STM6315 family.
That covers engine-bay electronics, outdoor telecom cabinets, factory-floor sensors, and anything that sees a hot summer day inside a sealed enclosure. The 125°C upper limit is the junction temperature for the silicon, not just ambient — so in a system that self-heats, you still have margin before the part derates or fails.
Housed in a SOT-143-4 package (TO-253-4 / TO-253AA), this is a four-pin surface-mount device. The SOT-143 footprint is common and easy to hand-solder for prototypes, but the small body means the open-drain pull-up resistor should sit close to the pin to keep the trace short — otherwise the output rise time stretches noticeably with even a few pF of trace capacitance.
Lifecycle status — no LTB pressure here
There's no last-time-buy notice, no end-of-life announcement, and no successor part to worry about.