SLVSHH9 February 2024 TPS54KC23
PRODUCTION DATA
To calculate the value of the output inductor (LOUT), use Equation 12. The output capacitor filters the inductor-ripple current (IRIPPLE), Equation 13. Therefore, selecting a high inductor-ripple current impacts the selection of the output capacitor because the output capacitor must have a ripple-current rating equal to or greater than the inductor-ripple current. Larger ripple current increases output ripple voltage, but improves signal-to-noise ratio and helps to stabilize operation. Generally speaking, the inductance value must set the ripple current at approximately 15% to 40% of the maximum output current for a balanced performance.
For this design, the inductor-ripple current is set to 20% of 30A output current. With a 800kHz switching frequency, 16V as maximum VIN, and 0.8V as the output voltage, the calculated inductance is 0.16μH. An inductance value of 0.15µH is chosen.
The inductor requires a low DCR to achieve good efficiency. The inductor also requires enough room above peak inductor current before saturation. The peak inductor current is estimated using Equation 14. Peak inductor current under maximum VIN is calculated as 33.2A. Equation 15 calculates the RMS current in the inductor and the heat current rating of the inductor must be greater than this.