A lossless current sensing technique is proposed, which takes advantage of the on-resistance of the sync FET used in the buck converter to sense the current flowing through the device and to reconstruct an emulated version of the inductor current. The current sensing circuit is integrated into the MOSFET driver and co-packaged with a set of FETs in a stacked die arrangement with common lead-frame shared between driver and sync FET to enable accuracy equivalent to or better than DCR sensing. In addition to steady-state operation, modern multiphase controllers are required to drive the buck converter in other operating modes including: Diode Emulation Mode (DEM), body-braking, tri-state (phase off). These additional modes are also correctly emulated by the current sense logic.