High-level design of a digital current sensor using multibit sigma-delta modulation

The sigma-delta modulation has become the standard A/D conversion for most applications requiring high resolution. A recent extension of this principle consists in replacing the first stage of the modulator (a servo-controlled adder) by a physical opposition cell. The expected benefits for digital sensors are high resolution as well as improved linearity. In this paper, the high-level design of a sigma-delta, current sensor is proposed. It is based upon a Hall effect cell included in a 3-bit second-order sigma-delta modulator. In order to counterbalance the limitations induced by the physical cell, a design method based on the continuous-time synthesis has been developed and validated considering achieved resolution and bandwidth performances.