FUJITSU MB39A104 - Manual (Page 27)

MB39A104
27
Example:
CH1
CH2
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. It is therefore
necessary to determine the load level at which continuous operation becomes possible. In this application, the
Sumida CDRH104R-150 is used. At 15
µH, the load current value under continuous operating conditions is
determined by the following formula.
Load current value under continuous operating conditions : I
O
Example: Using the CDRH104R-150
15
µH (allowable tolerance ±30%) , rated current = 3.6 A
CH1
CH2
L ≥
2 (V
IN
− V
O
)
ton
I
O
≥
2 Ч (19 − 5)
Ч
1
Ч 0.263
I
O
500
× 10
3
≥ 4.91 µH
L ≥
2 (V
IN
− V
O
)
ton
I
O
≥
2
Ч (19 − 3.3)
Ч
1
Ч 0.174
I
O
500
× 10 3
≥ 3.64 µH
I
O
≥
V
O
toff
2L
I
O
≥
V
O
toff
2L
≥
5
Ч
1
Ч (1 − 0.263)
2
Ч 15 Ч 10 −6 500
Ч 10
3
≥ 245.7 mA
I
O
≥
V
O
toff
2L
≥
3.3
Ч
1
Ч (1 − 0.174)
2
Ч 15 Ч 10 −6 500
Ч 10
3
≥ 181.7 mA