MB39C308 Datasheet, PDF (33/60 Pages) Fujitsu Component Limited. – 6ch DC/DC Converter IC for LPIA Platform VR

MB39C308
• Input Capacitor Selection
Because this IC uses the C-Mode system, it is recommended to use ceramic capacitors with a small ESR. See
the “■ RECOMMENDED OPERATING CONDITIONS” for the value of the capacitance.
• Output Capacitor Selection
Because this IC uses the C-Mode system, it is recommended to use ceramic capacitors with a small ESR. See
the “■ RECOMMENDED OPERATING CONDITIONS” for the value of the capacitance.
• Bootstrap Diode Selection
It is not necessary to connect diode to the outside device normally because this device contains a bootstrap
diode. However, it is recommended to add a shotkey barrier diode (SBD) when 4 V drive products is used for
CH1 and CH2 switching FET. In this case, select the smallest forward current possible and connect as the figure
below.
• When adding bootstrap SBD to CH1
CB1
VB
The current to drive on the gate of high-side FET flows to the SBD of the bootstrap diode. The average current
can be found by the following formula. However, set the current which does not exceed the maximum rating.
ID ≥ Qg × fOSC
ID : Forward current [A]
Qg : Total gate electric charge of high-side FET [C]
fOSC : Switching frequency [Hz]
The voltage rating of bootstrap capacitor can be found by the following formula.
VR_BOOT > VDD
VR_BOOT : Bootstrap diode DC reverse voltage [V]
VDD : Switching power supply voltage [V]
DS04-27261-6E
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