What this overvoltage protection controller does on the board
The MAX4840AEXT+T is an overvoltage protection controller from Analog Devices, designed to monitor the input voltage rail and disconnect the load when the supply exceeds a safe threshold. It sits between the power source and the downstream circuitry, acting as a fast-acting electronic fuse that opens before the overvoltage reaches sensitive components. Target applications include cell phones, digital cameras, and media players — portable devices where a faulty charger or a transient on the USB bus could damage the battery charger IC or the main PMIC. The controller's job is to pull the gate of an external N-channel MOSFET low when the input voltage rises above the trip point, isolating the protected rail.
Housed in a 6-TSSOP / SC-88 / SOT-363 package, the supplier device package is SC-70-6 — a compact 6-lead surface-mount package with 0.65 mm pitch.