Wide application of step-down switching power supply

Although adding a filter circuit can reduce noise, it occupies a larger PCB area. Since the conversion efficiency of the 1.8V output switching power supply is lower than that of the 3.3V output switching circuit, the heat loss is greater. In addition, it needs to be boosted to provide a 3.3V/2A power supply, which further aggravates the heating problem. If the step-down circuit shown in Figure 4-3 is used, the DC/DC conversion module provides a 3.3V power supply. Since the minimum bias voltage of the MAX1714 in the figure is not less than 4.5V, a boost chip needs to be added to convert 3.3V to 5V, and the 5V power supply required by the internal control and bias circuits of the MAX1714 only requires less than 40 mA of current.

Therefore, the problem can be solved by using the charge pump power supply MAX619 shown by the dotted line in the figure. Because MAX1714 uses synchronous switching rectification technology, the conversion efficiency is about 7 to 8 percentage points higher than that of ordinary converters, so the conversion efficiency of its power supply can be as high as more than 90%.