MB39A104_06 Datasheet, PDF (28/38 Pages) Fujitsu Component Limited. – 2-ch DC/DC Converter IC with Overcurrent Protection

MB39A104
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
IL ≥ IO +
VIN − VO
2L
ton
Peak-to-peak value : ∆IL
∆IL =
VIN − VO
L
ton
Example: Using the CDRH104R-150
15 µH (allowable tolerance ±30%) , rated current = 3.6 A
Peak value:
CH1
IL ≥ IO +
≥3+
VIN − VO
2L
ton
19 − 5
2 × 15 × 10^−6
×
1
500 × 10³
× 0.263
≥ 3.25 A
CH2
IL ≥ IO +
≥3+
VIN − VO
2L
ton
19 − 3.3
2 × 15 × 10^−6
×
1
500 × 10³
× 0.174
≥ 3.18 A
Peak-to-peak value:
CH1
∆IL =
VIN − VO
L
ton
=
19 − 5
15 × 10^−6
×
1
500 × 10³
× 0.263
= 0.491 A
CH2
∆IL =
VIN − VO
L
ton
=
19 − 3.3
15 × 10^−6
×
1
500 × 10³
× 0.174
= 0.364 A
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