Analysis of Lossless Current Sensing Techniques with High Accuracy and Linearity

Several lossless current sensing techniques have been proposed in literatures and adopted by the industries in recent years. However, none of these solutions have addressed the issue of uniform sense accuracy. In this paper, an in-depth analysis of the lossless current sensing technique implemented in a dc-dc buck converter is presented. The compensation techniques for achieving a uniform sense-ratio are discussed and analyzed using two different current sense circuit topologies. The sense circuits are designed using the AMS 0.35 um, 4 metals, double poly CMOS process. Using the same technology and operating under the same electrical conditions, the simulation results show that the proposed sense circuits achieved a maximum sense accuracy of 99%, compared to 95% achieved using the conventional approach.