The TPS259540DSGT is a Texas Instruments electronic fuse that covers the common intermediate bus rails: 3.3 V, 5 V, 12 V, and up to 18 V nominal. The 4 A continuous output rating sets the load budget for the protected rail — budget derating above 85 °C ambient, as the package thermal impedance (exposed pad on 8-WSON 2x2 mm) limits the power dissipation at the high end of the 2.7 V to 18 V input range.
±7.5 % current-limit accuracy — tighter than the typical eFuse
The ±7.5 % accuracy on the current limit means you can set the threshold closer to the load's maximum draw without tripping on inrush or transient peaks. For a 4 A rail, a ±7.5 % band translates to a ±300 mA window — enough headroom to avoid nuisance trips on most capacitive loads.
Package and rework — 8-WSON with exposed pad
It reflows well with a standard solder profile, but the pad under the part needs a thermal via array to pull heat into the board plane — without it the junction temperature rises fast above 4 A continuous.
The 125 °C junction ceiling means the part can run at full 4 A output only if the board-level thermal design keeps the junction below that limit — derate the output current above 85 °C ambient based on the package's thermal resistance.