Fujitsu MB39A105 manual 2LV O

MB39A105

Example:

L ≥	VIN (Max)	2	ton
	2IOVO
≥	42			⋅	9−4	⋅	1
	2 ⋅ 0.25 ⋅ 9				9		500 ⋅ 103

≥3.95 ∝H

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 CMD5D13-6R8 is used. At 6.8 ∝H, the load current value under continuous operating conditions is determined by the following formula.

Load current value under continuous operating conditions : IO

IO ≥	VIN (Max) 2
		ton
	2LVO
≥	42		⋅	9−4	⋅	1
	2 ⋅ 6.8 ⋅ 10−6 ⋅ 9			9		500 ⋅ 103

≥145.2 mA

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	≥	VO ⋅ IO		+	VIN	ton	ton =	VO − VIN	t
		VIN			2L			VO
Peak-to-peak value : ΔIL
ΔIL	=	VIN	ton
		L

Example: Using the CMD5D13-6R8

6.8 ∝H (allowable tolerance ±20%) , rated current = 1.4 A

Peak value:

IL ≥

VO ⋅ IO

+

VIN

ton

ton =

VO − VIN

t

VIN

2L

VO

≥

9 ⋅ 0.25

+

2.4 ⋅

(9 − 2.4)

⋅

1

2.4

2 ⋅ 6.8

⋅ 10−6 ⋅ 9

500 ⋅ 103

≥1.20 A

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