The MAX836EUS+T is a single-channel supervisor in a 4-pin SOT-143-4 package — the same footprint as a small-signal transistor, so it fits into tight power-sequencing slots on mixed-voltage boards. The open-drain output pulls low on a reset event, which means it can be wire-ORed with other supervisors or pulled up to a different rail than the IC's supply.
What the adjustable threshold buys you
The voltage threshold is adjustable/selectable via external resistors — you set the trip point to match the core voltage of whatever processor or FPGA you're monitoring, rather than being locked into a fixed threshold. The 80 µs typical propagation delay means the reset asserts fast enough to catch a brownout before the downstream logic enters an undefined state, but not so fast that it triggers on supply noise.