L6739 Datasheet, PDF (26/30 Pages) STMicroelectronics – CPU and DSP power supply

Application information
L6739
10.3
Input capacitors
The input capacitor bank is designed considering mainly the input RMS current that
depends on the output deliverable current (I_OUT) and the duty cycle (D) for the regulation as
follows:
Equation 18
I_rms = I_OUT  D  1 – D
The equation reaches its maximum value, I_OUT / 2, with D = 0.5. The losses depend on the
input capacitor ESR and, in the worst case, are:
Equation 19
P = ESR  I_OUT  2²
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