What this supervisor does on the rail
The MAX6458UKD3C+T is a single-channel voltage supervisor from Maxim Integrated — a Simple Reset/Power-On Reset IC that monitors a single supply rail and holds the reset output active-low until the voltage has been stable for at least 90 ms. The open-drain output lets you wire-OR it with other reset signals or pull it up to a different logic voltage. It comes in a SOT-23-5 package, rated for -40°C to 125°C, so it fits industrial control boards, motor drives, and anything that sees a hot enclosure.
90 ms timeout — what it buys you
The 90 ms minimum reset timeout is the window the supervisor gives the power rail to settle after it crosses the threshold. If your supply has a slow ramp or a capacitor bank that takes tens of milliseconds to charge, this part won't release the reset early and let the MCU start running on a brown rail. That 90 ms floor is a minimum — the actual timeout can be longer, but you design for the floor.
Open-drain output — pull-up required
Because the output is open drain, it cannot source current — it only pulls the line low when reset is asserted. An external pull-up resistor to the MCU's VDD (or to any rail up to the absolute maximum) is required to hold the reset line high during normal operation.