Power metal oxide semiconductor field effect transistors with accurate current sensing function over a wide temperature range

In the power metal oxide semiconductor field effect transistor (MOSFETs) with a current-sensing function (current-sensing power MOSFETs), temperature dependence in the current sense ratio has been a significant problem. The authors discuss the mechanisms involved in these temperature-dependent current sense ratios by investigating the following factors: (i) drift layer impurity concentration and layer thickness and (ii) chip size and the position of the sense MOSFET part in the chip. Furthermore, it is shown that temperature dependence in the sense ratio can be reduced by adopting a floating island and thick bottom oxide trench gate MOSFET (FITMOS) structure or by arranging the sense MOSFET part at the centre of the chip.