FUJITSU MB39A104 - Manual (Page 28)

MB39A104
28
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
Peak-to-peak value :
∆I
L
Example: Using the CDRH104R-150
15
µH (allowable tolerance ±30%) , rated current = 3.6 A
Peak value:
CH1
CH2
Peak-to-peak value:
CH1
CH2
I
L
≥ I
O
+
V
IN
− V
O
ton
2L
∆I
L
=
V
IN
− V
O
ton
L
I
L
≥ I
O
+
V
IN
− V
O
ton
2L
≥ 3 +
19 − 5
Ч
1
Ч 0.263
2
Ч 15 Ч 10 −6 500
Ч 10
3
≥ 3.25 A
I
L
≥ I
O
+
V
IN
− V
O
ton
2L
≥ 3 +
19
− 3.3
Ч
1
Ч 0.174
2
Ч 15 Ч 10 −6 500
Ч 10 3
≥ 3.18 A
∆I
L
=
V
IN
− V
O
ton
L
=
19 − 5
Ч
1
Ч 0.263
15
Ч 10 −6 500
Ч 10
3
= 0.491 A
∆I
L
=
V
IN
− V
O
ton
L
=
19
− 3.3
Ч
1
Ч 0.174
15
Ч 10 −6 500
Ч 10 3
= 0.364 A