Step-up Switching Regulator with Integrated Current Limit

In the form of the LT1618, Linear Technology (www.lineartech.com) has made available a step-up switching regulator with a current limit mechanism. This makes it easy to protect an otherwise not short-circuit-proof switching regulator: the input voltage is always connected to the output via an inductor and a diode. We can limit the current at the input (Figure 1), which limits the current drawn by the entire circuit; alternatively, with the circuit of Figure 2, the output current can be limited. This enables the design of constant current sources at voltages higher than the input voltage. In the circuit shown the nominal output voltage of the step-up switching regulator will be around 22 V.