JAJS298D DECEMBER 2003 – June 2019 TPS54110
PRODUCTION DATA.
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Use Equation 7 to calculate the minimum value of the output inductor:
KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum output current. For designs using low-ESR capacitors such as ceramics, use KIND = 0.2. When using higher ESR output capacitors, KIND = 0.1 yields better results. If higher ripple currents can be tolerated, KIND can be increased allowing for a smaller output-inductor value.
This example design uses KIND = 0.2, yielding a minimum inductor value of 6.29 µH. The next-higher standard value of 6.8 µH is chosen for this design. If a lower inductor value is desired, a larger amount of ripple current must be tolerated.
The RMS-current and saturation-current ratings of the output filter inductor must not be exceeded. The RMS inductor current can be found from Equation 8:
The peak inductor current is determined from Equation 9:
For this design, the RMS inductor current is 1.503 A and the peak inductor current is 1.673 A. The inductor chosen is a Coilcraft DS3316P-682 6.8 µH. It has a saturation current rating of 2.8 A and an RMS current rating of 2.2 A, easily meeting these requirements.