A FEM Approach for Mitigating Magnetic Crosstalk for an Embedded Current Sensor

Accurate measurements of the current sharing between parallel dies are essential when designing compact fast switching multichip power modules. A two-stage current sensor has been demonstrated which due to its embedded current transformers can be integrated inside a power module and used for individual die current measurements. However, parasitic magnetic couplings between the current transformers and the layout has been observed which during switching of the dies yield an undesired crosstalk current in the current sensors. A finite element method based crosstalk mitigation strategy is proposed where the parasitic magnetic couplings are estimated using Ansys Maxwell. Through equations describing the different contributions to the induced current in the secondary winding of each current transformer, the crosstalk current’s contribution can be mitigated, leading to an improved sensor accuracy. The mitigation strategy is tested and verified by comparing the total die current measured with a Rogowski coil to the summation of the individual die currents with and without applying the mitigation strategy.