MB39A106 Datasheet, PDF (33/46 Pages) Fujitsu Component Limited. – 2-Channel DC/DC Converter IC with Overcurrent Protection Symmetrical-Phase Type

MB39A106
CH2 (Synchronous rectification side)
Input voltage VIN (Max) = 15 V, output voltage VO = 5 V, drain current ID = 3 A, Oscillation frequency fOSC = 300
kHz, L = 22 µH, drain-source on resistance RDS (ON) =: 28 mΩ, tr = 16.4 ns, tf = 5.2 ns.
Drain current (Max) : ID (Max)
ID (Max) = IO +
VO
2L
toff
=3 +
5
2 × 22 × 10^−6
=: 3.25 (A)
×
1
300 × 10³
×
(1−0.33)
ID (Min) = IO −
VO
2L
toff
=3
−
5
2 × 22 × 10^−6
×
1
300 × 10³
×
(1−0.33)
=: 2.75 (A)
PC2 = ID2 × RDS (ON) × Duty (OFF)
= 3² × 0.028 × (1−0.33)
=: 0.169 W
PS2 (ON)
=
VD (Max) × ID × tr × fOSC
6
=
15 × 3 × 16.4 × 10^−9 × 300 × 10³
6
=: 0.037 W
PS2 (OFF)
=
VD (Max) × ID (Max) × tf × fOSC
6
=
15 × 3.25 × 5.2 × 10^−9 × 300 × 10³
6
=: 0.013 W
PT2 = PC2 + PS2 (ON) + PS2 (OFF)
=: 0.169 + 0.037 + 0.013
=: 0.219 W
PT = PT1 + PT2 (OFF)
=: 0.149 + 0.219
=: 0.368 W
The above power dissipation figures for the IRF7901D1 are satisfied with ample margin at 2W (Ta = +100 °C) .
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