Compensation of Assembly Tolerances in Magnetic Current Sensors with External Conductor

Small-sized SMD current sensor ICs offer a cost effective solution for several current sensing applications utilizing standard printed circuit board (PCB) technology. The key to measurement-range scalability is to use a current rail external to the sensor package instead of being an integral part of the package. However, state of the art PCB mounting processes show assembly tolerances, which may cause several percent of error in the sensitivity. Such level of errors is usually not tolerable by the electronics manufacturers, so the best they can do is a final End-Of-Line (EOL) calibration after mounting, where specific current levels need to be set accurately and forced through the device. This paper presents the idea of compensation of assembly tolerances as a potential counteraction already on IC-level. The method itself is based on additional sensing-elements integrated onto the die beside the main ones: their signals are combined with the main sensor signals to get the compensated current signal. Adopting this principle, the costly and time-consuming EOL calibration can be abandoned resulting in increased IC-product value