MB39A112 Datasheet, PDF (28/35 Pages) Fujitsu Component Limited. – 3-ch DC/DC Converter IC

MB39A112
• Flyback diode
The flyback diode is generally used as a Shottky barrier diode (SBD) when the reverse voltage to the diode is
less than 40 V. The SBD has the characteristics of higher speed in terms of faster reverse recovery time, and
lower forward voltage, and is ideal for archiving high efficiency. As long as the DC reverse voltage is sufficiently
higher than the input voltage, the average current flowing through the diode is within the average output current
level, and peak current is within peak surge current limits, there is no problem. In this application the SANYO
SBE001, SBS005 are used. The diode average current and diode peak current can be calculated by the following
formulas.
Diode mean current : IDi
Vo
IDi ≥ Io × ( 1 −
)
VIN
Diode peak current : IDip
Vo
IDip ≥ (Io +
tOFF)
2L
Example : Using the SBE001
VR (DC reverse voltage) = 30 V, average output current = 2.0 A, peak surge current = 20 A,
VF (forward voltage) = 0.55 V, at IF = 2.0 A
• CH1
Diode mean current
Vo1
IDi ≥ Io × (1 −
)
VIN
≥ 1.5 × (1 − 0.1)
≥ 1.35 A
Diode peak current
Vo1
IDip ≥ (Io +
tOFF)
2L
≥ 1.61 A
• CH2
Diode mean current
Vo2
IDi ≥ Io × (1 −
)
VIN
≥ 1.0 × (1 − 0.275)
≥ 0.725 A
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