JAJSH64B November 2012 – April 2019 TPS53819A
PRODUCTION DATA.
Determined the inducatance to yield a ripple current (IIND(ripple)) of approximately ¼ to ½ of maximum output current. Larger ripple current increases output ripple voltage, improves the signal-to-noise ratio and helps stable operation. Maximum current ripple occurs with the maximum input voltage. Equation 9 calculates the recommended inductance. After choosing the inductance, use Equation 10 to calculate the ripple.
The inductor requires a low DCR to achieve good efficiency. The inductor also requires enough margin above the peak inductor current before saturation. The peak inductor current can be estimated in Equation 11.
Using Equation 9 the recommended inductance for the example is 0.329 μH. An inductor supplied by Pulse Electronics (PA0513.441NLT) is selected with an inductance of 0.440 μH at 0 A and 0.363 μH at its 30 A rated current. The saturation current is 35 A and the DCR is 0.32 mΩ. Using Equation 10 with the selected inductance and maximum input voltage, the current ripple is estimated to be 6.23 A. Equation 11 calculates the peak current to be 31.3 A, well below the saturation current of the inductor. The output current threshold when the supply operates in DCM or CCM can also be estimated as half the estimated current ripple. With the maximum 14 V input in this design the output current threshold is 3.12 A. With lower input voltages, ripple decreases and so does the threshold.