Taming Linear-Regulator Inrush Currents

Historically, design engineers chose linear regulators for their low cost, simplicity, low noise, and high PSRR, rarely considering a regulator's ability to control inrush current at start-up. This oversight sometimes rendered the input power supply unable to supply enough start-up current, especially if the regulator had a large output capacitance. To continue going forward, designers had to use external circuitry to provide inrush-current control. Today, however, they can choose from a new generation of linear regulators with integrated soft start/inrush-current control. Taking soft start into consideration early in the design phase provides a problem-free system with controlled, predictable inrush current at start-up.