A very interesting integrated circuit for step-down converter designs (voltage reducers) with an output current capacity of up to 2 A is the LT3481 from Linear Technology (www.linear.com). This component has an input voltage range of 3.6 V to 34 V with a maximum of 36 V and a switching frequency of 2.8 MHz. In burst mode operation the ripple with 50 uA Iq, 12 V input and 3.3 V output. This ripple under these conditions is less than 15 mV. The boost diode is integrated and the feedback reference voltage is 1,265 V. The device can supply output voltages from 1,265 V to 20 V and has soft start capabilities. The power switch included on the chip has a resistance of only 0.18 ohms which leads the device to achieve high efficiencies, above 80% at full load. In figure 1 we have an application circuit for an input of 6.3 V to 34 V and an output of 5 V.
For 3.3 V and 2.5 V outputs with inputs in the 4 to 34 V range, we have the two circuits shown in figure 5. In all cases, we have shutdown features that reduce consumption to less than 1 uA. The device is supplied in a 10-pin MSOP enclosure as well as DFN.
