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Power loss calculation with CSI consideration for synchronous buck converters (Rev. A)


The synchronous buck converter is a widely used topology in low-voltage, high-current applications. Low-power loss and highly efficient synchronous buck converters are in great demand for advanced microprocessors of the future. Good understanding of power losses in a synchronous buck converter is critical for improving converter performance. Common source inductance (CSI) is the inductance shared by the main current path and the gate driver loop in a converter and carries the drain-source current and the gate-charging current. A high-side (HS) FET CSI has significant impact on converter performance, especially switching power loss: the greater the HS CSI, the greater the switching loss. This application report analyzes MOSFET-related power losses in a synchronous buck converter. The effects of HS CSI are also discussed and quantified.