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
VIN − VO
IL ≥ IO +
ton
2L
Peak-to-peak value : ∆IL
VIN − VO
∆IL
=
ton
L
Example: Using the CDRH104R-150
15 µH (allowable tolerance ±30%) , rated current = 3.6 A
Peak value:
CH1
VIN − VO
ton
IL ≥ IO +
2L
19 − 5
1
× 0.263
≥ 3 +
2 × 15 × 10−6 × 500 × 103
≥ 3.25 A
CH2
VIN − VO
IL ≥ IO +
ton
2L
19 − 3.3
2 × 15 × 10−6
1
≥ 3 +
×
× 0.174
500 × 103
≥ 3.18 A
Peak-to-peak value:
CH1
VIN − VO
∆IL =
ton
L
19 − 5
1
=
× 0.263
15 × 10−6 × 500 × 103
= 0.491 A
CH2
VIN − VO
∆IL
=
ton
L
19 − 3.3
15 × 10−6
1
=
×
× 0.174
500 × 103
= 0.364 A
28
FUJITSU [ FUJITSU ]
