SLUSAU4B DECEMBER 2011 – February 2019 TPS53219A
Selecting external components is a simple process using D-CAP Mode.
The inductance should be determined to give the ripple current of approximately ¼ to ½ of maximum output current. Larger ripple current increases output ripple voltage and improves the signal-to-noise ratio and helps stable operation.
The inductor also requires a low DCR to achieve good efficiency. It also requires enough room above the peak inductor current before saturation. The peak inductor current can be estimated in Equation 10.
When organic semiconductor capacitors or specialty polymer capacitors are used, for loop stability, capacitance and ESR should satisfy Equation 2. For jitter performance, Equation 11 is a good starting point to determine ESR.
The output voltage is programmed by the voltage-divider resistor, R1 and R2 shown in Figure 17. R1 is connected between the VFB pin and the output, and R2 is connected between the VFB pin and GND. Recommended R2 value is between 10 kΩ and 20 kΩ. Determine R1 using Equation 12.