Sense fet having a selectable sense current ratio and method of manufacturing the same

Abstract

A sense FET is provided that is capable of achieving one of many available sense current ratios after manufacture, and a method of manufacturing the same. The sense FET includes a main cell array of MOSFET cells connected in parallel, and a main pad connected to the sources of the main cells. A plurality of unit sense cells are arranged in arrays, and also optionally in groups corresponding to portions of the arrays. A plurality of sense pads are electrically insulated from each other. Each sense pad is connected to the sources of the unit sense cells of either a complete sense cell array, or of a group corresponding to a portion of an array. Every sense pad is connected either to the sense resistor or to the main pad. When connected to a sense resistor, the corresponding unit cells are used as sense cells. For every different combination of sense pads that are connected to the sense resistor, a different number of unit cells are used as sense cells, and therefore a different sense current ratio is effectuated for the device. Connection to the sense resistor is by a reconfigurable wire bonding process, or by cutting electrically metal thin film fuses that initially connect the sense pads. The fuses can also initially join the sense pads to the main pad. This way the unit cells of unused sense pads can act instead as main cells.