MB39A113 Datasheet, PDF (33/51 Pages) Fujitsu Component Limited. – ASSP for Power Supply Applications (Secondary Battery)

MB39A113
Example) Using the CDRH104R-150
15 µH (tolerance ± 30%) , rated current = 3.6 A
Peak value
16.8 V output
VIN−Vo
IL ≥ Io +
tON
2L
≥ 3+
25−16.8
2 × 15 × 10^−6
≥ 3.6 A
1
×
× 0.672
300 × 10³
12.6 V output
VIN−Vo
IL ≥ Io +
tON
2L
≥ 3+
22−12.6
2 × 15 × 10^−6
≥ 3.6 A
1
×
× 0.572
300 × 10³
Peak-peak value
16.8 V output
∆IL =
VIN−Vo
L
25−16.8
=
15 × 10^−6
=: 1.22 A
tON
1
×
× 0.672
300 × 10³
12.6 V output
∆IL =
VIN−Vo
L
22−12.6
=
15 × 10^−6
=: 1.2 A
tON
1
×
× 0.572
300 × 10³
• Flyback diode
As a flyback diode, in general, a Schottky barrier diode (SBD) is used when the reverse voltage to the diode is
40 V or less. The SBD has the characteristic of higher speed in terms of faster reverse recovery time, and lower
forward voltage, and is ideal for archiving high efficiency. There is no problem as long as the DC reverse voltage
is sufficiently higher than the input voltage, and the mean current flowing during the diode conduction time is
within the mean output current level, and as the peak current is within the peak surge current limits.
In this application the RB053L-30 (ROHM) are used. The diode mean current and diode peak current can be
obtained by the following formulas.
Diode mean current : IDi
Vo
IDi ≥ Io × (1−
)
VIN
Diode peak current : IDip
Vo
IDip ≥ (Io +
2L
tOFF)
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