The LTC3559EUD-1#PBF comes in a 16-WFQFN exposed pad package (3x3 mm body), surface-mount only. The exposed pad under the QFN needs a thermal land on the PCB with vias to a ground plane — without it the charge current rating at 85°C ambient drops. No lab bench required for a field swap if the pad is pre-tinned and the board has a solder stencil; hot-air rework is the tool here, not a soldering iron. It is a single-cell Lithium Ion/Polymer charger with a programmable constant-current profile, maxing out at 950 mA. The USB interface means it negotiates power from a standard USB port — the supply voltage tops out at 5.5 V, so a 5 V rail is fine, but a 5 V wall wart that drifts above 5.5 V will hit the abs-max.
Analog Devices lists this part as Active.