WIDE INPUT 3A STEP-DOWN CONVERTER

2007-1-4

4/10

FSP3128

TYPICAL APPLICATION CIRCUIT

APPLICATION INFORMATION

Output Voltage Setting

Figure 1 shows the connections for setting the output voltage. Select the proper ratio of the two feedback resistors

Figure 1 Output Voltage Setting

Inductor Selection

The inductor maintains a continuous current to the output load. This inductor current has a ripple that is dependent on

the inductance value: higher inductance reduces the peak-to-peak ripple current. The trade off for high inductance

value is the increase in inductor core size and series resistance, and the reduction in current handling capability. In

general, select an inductance value L based on ripple current requirement.

peak-to-peak ripple current being a percentage of the maximum output current. With this inductor value (Table 1), the

Finally, select the inductor core size so that it does not saturate at 5A.

1.5V

1.8V

2.5V

3.3V

5V

L

6.8µ H6.8µ H6.8µ H8.5µ H15µ H

Table 1: Typical Inductor Values