Fujitsu MB39A104 manual Example

MB39A104

Example:
CH1	2 (VIN − VO)
L ≥		ton
	IO
≥	2 ⋅ (19 − 5)	⋅	1	⋅ 0.263
	IO		500 ⋅ 103

≥4.91 ∝H

CH2	2 (VIN − VO)
L ≥		ton
	IO
≥	2 ⋅ (19 − 3.3)	⋅	1	⋅ 0.174
	IO		500 ⋅ 103

≥3.64 ∝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 CDRH104R-150 is used. At 15 ∝H, the load current value under continuous operating conditions is determined by the following formula.

Load current value under continuous operating conditions : IO

IO ≥ VO toff 2L

Example: Using the CDRH104R-150

15 ∝H (allowable tolerance ±30%) , rated current = 3.6 A

CH1

IO ≥ VO toff 2L

≥	5	⋅	1	⋅ (1 − 0.263)
	2 ⋅ 15 ⋅ 10−6		500 ⋅ 103

≥245.7 mA

CH2
IO ≥	VO		toff
	2L
≥		3.3		1		⋅ (1 − 0.174)
				⋅
	2 ⋅ 15 ⋅ 10−6				500 ⋅ 103

≥181.7 mA

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