A complete step-down regulator can be designed in a few simple steps using the nomographs and tables in this data sheet (or use the available design software at www.ti.com).

Step 1: Define the power supply operating conditions:

• Required output voltage
• Maximum DC input voltage
• Maximum output load current

Step 2: Set the output voltage by selecting a fixed output LM2676 (3.3-V, 5-V or 12-V applications) or determine the required feedback resistors for use with the adjustable LM2676-ADJ.

Step 3: Determine the inductor required by using one of the four nomographs (Figure 8-2 through Figure 8-5). Table 8-3 provides a specific manufacturer and part number for the inductor.

Step 4: Using Table 8-5 and Table 8-6 (fixed output voltage) or Table 8-9 and Table 8-10 (adjustable output voltage), determine the output capacitance required for stable operation. Table 8-1 and Table 8-2 provide the specific capacitor type from the manufacturer of choice.

Step 5: Determine an input capacitor from Table 8-7 or Table 8-8 for fixed output voltage applications. Use Table 8-1 or Table 8-2 to find the specific capacitor type. For adjustable output circuits, select a capacitor from Table 8-1 or Table 8-2 with a sufficient working voltage (WV) rating greater than V_IN max, and an RMS current rating greater than one-half the maximum load current (two or more capacitors in parallel can be required).

Step 6: Select a diode from Table 8-4. The current rating of which must be greater than I_LOAD max and the reverse voltage rating must be greater than V_IN max.

Step 7: Include a 0.01-µF, 50-V capacitor for C_BOOST in the design.