An inrush current is an instantaneous input current surge drawn by an electrical device, measured during the initial turn-on of the power supply. This current reduces to a lower steady-state current once the input capacitors charge. There are multiple ways to limit the inrush current pertinent, because uncontrolled inrush can damage components, lowering the available supply voltage to other circuits, and causing system errors. A few ways of controlling the inrush current include: Over designing the power supply to accommodate the inrush current, Building an external soft start circuit with power FET with RC circuit, or Using a power supply with a built-in circuit to slow down the start-up ramp rate (fixed or adjustable). The latter can serve as the easiest, most convenient, and economical solution to tackle inrush current issues. SIMPLE SWITCHER LMZ3 power modules contains integrated soft-start functionality which helps control the inrush current.