MB39A113 Datasheet, PDF (32/51 Pages) Fujitsu Component Limited. – ASSP for Power Supply Applications (Secondary Battery)

MB39A113
12.6 V output
Example)
2 (VIN (Max) −Vo)
L≥
tON
Io
2 × (22−12.6)
1
≥
×
× 0.572
3
300 × 10³
≥ 12.0 µH
Inductance values derived from the above formulas are values that provide sufficient margin for continuous
operation at maximum load current, but at which continuous operation is not possible at light-loads. So, it is
necessary to determine the load level at which continuous operation becomes possible. In this application, the
SUMIDA CDRH104R-150 is used. The following equation is available to obtain the load current as a continuous
current condition when 15 µH is used.
The load current value under continuous operating conditions : Io
Vo
Io ≥
tOFF
2L
Example) Using the CDRH104R-150
15 µH (tolerance ± 30%) , rated current = 3.6 A
16.8 V output
Vo
Io ≥
tOFF
2L
16.8
≥
2 × 15 × 10^−6
≥ 0.61 A
1
×
×
300 × 10³
(1−0.672)
12.6 V output
Vo
Io ≥
tOFF
2L
12.6
≥
2 × 15 × 10^−6
≥ 0.60 A
1
×
×
300 × 10³
(1−0.572)
To determine whether the current through the inductor is within rated values, it is necessary to determine the
peak value of the ripple current as well as the peak-to-peak values of the ripple current that affect the output
ripple voltage.
The peak value and peak-to-peak value of the ripple current can be determined by the following formulas.
Peak value : IL
VIN−Vo
IL ≥ Io +
tON
2L
Peak-peak value : ∆IL
VIN−Vo
∆IL =
tON
L
32