MB39A105 Datasheet, PDF (22/27 Pages) Fujitsu Component Limited. – 1-ch DC/DC Converter IC for low voltage

MB39A105
Peak-to-peak value:
∆IL =
VIN (Min)
L
ton
=
4 × (9 − 4)
6.8 × 10^−6 × 9
1
× 500 × 10³
=: 0.654 A
• Flyback diode
The flyback diode is generally used as a Shottky barrier diode (SBD) when the reverse voltage to the diode is
less than 40V. The SBD has the characteristics of higher speed in terms of faster reverse recovery time, and
lower forward voltage, and is ideal for achieving high efficiency. As long as the DC reverse voltage is sufficiently
higher than the output voltage, the average current flowing through the diode is within the mean output current
level, and peak current is within peak surge current limits, there is no problem. In this application the SANYO
SBS004 is used. The diode mean current and diode peak current can be calculated by the following formulas.
Diode mean current : IDi
IDi
≥ IO ×
(1 −
VO−VIN (Min)
VO
)
Diode peak current : IDip
IDip
≥
VO × IO
VIN (Min)
+
VIN (Min)
2L
ton
Example: Using the SANYO SBS004
VR (DC reverse voltage) = 15 V, mean output current = 1.0 A, peak surge current = 10 A,
VF (forward voltage) = 0.40 V, IF = 1.0 A
IDi
≥ IO × (1 −
VO−VIN (Min)
VO
)
≥ 0.25 × (1 − 0.733)
≥ 66.8 mA
IDip
≥
VO × IO
VIN (Min)
+
VIN (Min)
2L
ton
≥ 1.20 A
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