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Power Supplies 101 Slide 26

Now, the presentation will look at a few design examples, starting with an asynchronous peak current mode regulator. The high side switch is integrated into the package for this part, so it is not necessary to select a FET. This design example will use a VIN of 12V, a VOUT of 5V and an IOUT of 2A. The selected switching frequency is 1 MHz. R5 sets the resistor frequency according to the graph shown. A value of 18.2kΩ will give a FSW of 1 MHz. To set the output voltage, select R6 to be 10.5kΩ. From the feedback equation, R4 should be 42kΩ. Power train components and compensation components are selected via the table on the next slide. Based on the table, select C2 as 22μF, L1 as 4.7μH, R7 as 45.3kΩ, C5 as 0.47nF and C8 as 10pF. Other component values and selections are given in the datasheet. This includes C4, D1, C1, D2, and C7.

PTM Published on: 2011-09-27