ZHCSD62F December 2012 – May 2021 LM25017
PRODUCTION DATA
The minimum inductance is selected to limit the output ripple to 15 to 40 percent of the maximum load current. In addition, the peak inductor current at maximum load should be smaller than the minimum current limit as given in Section 6.5. The inductor current ripple is shown in Equation 10.
The maximum ripple is observed at maximum input voltage. To achieve the required output current of 650 mA without exceeding the peak current limit threshold, low ripple current is required. Substituting VIN = 48 V and ΔIL = 15 percent x IOUT (max) results in L1 = 169 μH. The higher value of 220 μH is chosen. The peak-to-peak minimum and maximum inductor current ripples of 19 mA and 75 mA at the minimum and maximum input voltages respectively. The peak inductor and switch current is shown in Equation 11.
688 mA is smaller than the minimum current limit threshold, which is 700 mA. The selected inductor should be able to operate at the maximum current limit of 1.3 A, during startup and overload conditions without saturating.