A shows a typical LTC 1148 surface-mount, application providing 5 V at 2 A from an input voltage of 5.5 V to 13.5 V. The operating efficiency, shown in B, peaks at 97% and exceeds 90% from 10 mA to 2 A with a 10-V input. Ql and Q2 comprise the main switch and synchronous switch, respectively, and inductor current is measured via the voltage drop across the current shunt. /vgENSE is the key component used to set the output, current capability according to the formula/QUT =100 mV/ftSENSE.
The advantages of current control include excellent line and load transient rejection, inherent short-circuit protection and controlled startup currents. Peak inductor current is limited to 150 mV//SENSE or 3 A for the circuit in A.