MB39C313 Datasheet, PDF (26/52 Pages) Fujitsu Component Limited. – 4ch System Power Management IC for LCD Panel

MB39C313
(2) Rectifier Diode Selection
Schottky diode should be used to attain high efficiency. The reverse voltage rating of the diode must be
higher than the maximum output voltage of the converter. Similar to Buck converter, the required averaged
rectified forward current of the Schottky diode is the product of off-time of Boost converter and the maximum
switch current at SW pin.
Vin
Off-time of Boost converter: D = 1 − D =
Vout
Vin
Maximum output current: Iavg = (1 − D) × ISWLIM
× ISWLIM
Vout
A Schottky diode with maximum rectified forward-current of 2A should be sufficient for most applications.
Another requirement for Schottky diode is the power dissipation. The power dissipation can be calculated
from the formula below:
PD = Iavg × VF = (1 − D) × ISWLIM × VF
Where
PD = power dissipation of the diode [W]
VF = diode forward voltage [V]
ISWLIM = minimum over current protection of SW-pin [A] (2.8 A)
(3) Output Capacitor Selection
Capacitors with low ESR are recommended. Ceramic capacitor which has low ESR is particularly suitable
for this purpose. Typically, three 22 μF ceramic capacitors connected in parallel are placed at the converter
output. More capacitance can be added so as to reduce voltage drop during heavy load transients.
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DS04–27267–1E