What this supervisor does — and where it fits
The MAX6381XR28D2+T is a single-channel voltage supervisor from Analog Devices, built to monitor a 2.8V supply rail and assert a reset signal when the voltage drops below that threshold. It is a Simple Reset/Power-On Reset type, meaning it holds the reset output low for a minimum of 20ms after the supply rises above the threshold — enough time for most MCUs, FPGAs, and SoCs to stabilise their internal oscillators and memory. The output is push-pull, active low, so it drives the reset pin directly without needing an external pull-up resistor. This is the kind of part you drop onto a 3.3V or 2.8V rail in an industrial controller, a telecom line card, or an automotive ECU where you need a clean, glitch-free power-on reset and brown-out detection across -40°C to 125°C.
2.8V threshold — what it means for the rail
The 2.8V threshold is set for monitoring a nominal 3.3V supply with margin. If your 3.3V rail dips below 2.8V, the supervisor pulls RESET low, holding the system in reset until the supply recovers and stays above 2.8V for at least 20ms. That 500mV guard band below 3.3V catches brown-out events before the logic rails collapse, without nuisance resets on normal ripple. For a 2.8V or 3.0V rail, the threshold is tighter — you would want a lower-voltage variant in the MAX6381 family. The single-voltage monitoring channel covers one rail; if you need to track multiple supplies, you would stack several of these or move to a multi-voltage supervisor.
Package and handling — SC-70-3
The SC-70-3 (also called SOT-323) package is a three-lead surface-mount part measuring roughly 2.0mm x 2.1mm. It is small enough for dense layouts but still hand-solderable with a fine-tip iron if you are careful. No exposed pad, so thermal management is through the leads — fine for the low quiescent current of a supervisor. The part ships in Tape & Reel or Cut Tape options, standard for pick-and-place. MSL rating is not in the record, but most SC-70 supervisors are MSL 1; still, if the reel has been open past the floor-life window, bake before reflow.
Lifecycle and sourcing
The MAX6381XR28D2+T is listed as Active with ROHS3 compliance. For BOM planning, this means no near-term obsolescence risk. If you need a second-source option, the MAX6381 family includes multiple threshold and timeout variants; a pin-compatible alternative with a different threshold (e.g., 3.0V or 1.8V) would require a different suffix, but the SC-70-3 footprint and pinout are consistent across the family.