A High Precision Current Sampling Circuit with Rail-to-Rail Common-Mode Input Range

Current information in the lithium-ion battery charging system is important for system control and can be used for overload protection, constant current control, status detection, etc. Since the number and status of cells are not fixed, conventional current sampling circuit is insufficient to the problems of low precision, limited common-mode input voltage range and difficult trim. In order to solve these problems, a symmetrical sampling structure with dual-path operation is proposed. This structure not only achieves a common-mode input range of -1 to 40V, but also has the advantages of high accuracy up to 95% and easy trimming.