A Digital Calibration Methodology And Its Application To A Hall Sensor Microsystem

Abstract

This paper presents a complete digital calibrationmethodology and its application to the improvement of a Hall sensor-based current measurement microsystem. It is a step-bystep illustration of how generic calibration techniques and circuits can be used on a practical example. First, the methodology is presented. The successive approximations algorithm and its working conditions are detailed. Circuits used for calibration are also discussed, as well as CAD tools useful for integrating background calibration components in electrical simulations. Then, the Hall sensor microsystem is analyzed at system level and its imperfections identified: sensitivity drift and offset drift. The circuit is designed so that for each imperfection to be cancelled, detection and compensation nodes are identified. To these nodes, generic digital calibration circuits are connected to perform continuous background calibration. In the presented current measurement microsystem, the use of the calibration methodology reduced the sensitivity drift down to 50 ppm/C, which is 10 times less than the state of the art.