Fujitsu MB39A104 Datasheet page 28

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