The circuit is based on IC1, an LTC1430 PWM controller. The current-limiting feature of the IC operates by sensing the voltage across the high-side MOSFET and compares it with a threshold voltage developed across R3.
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The circuit in Figure 1 uses the MIC2545A-2 and the MIC2778. The MIC2545A-2 is a programmable current limit high-side switch that is capable of having current-limit up to 2.5A.
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You can add a simple, two-transistor circuit to a standard, step-down dc/dc converter to provide an adjustable limit for the output current (Figure 1). You can apply this method to most step-down converters that provide access to the feedback node.
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