MB39A104
PC = ID 2 × RDS (ON) × Duty
=
3
2 × 0.05 × 0.263
=: 0.118 W
VD (Max) × ID × tr × fOSC
PS (ON)
=
=
6
19 × 3 × 100 × 10−9 × 500 × 103
6
=: 0.475 W
VD (Max) × ID (Max) × tf × fOSC
PS (OFF)
=
6
19 × 3.25 × 100 × 10−9 × 500 × 103
=
6
=: 0.515 W
PT
= PC + PS (ON) + PS (OFF)
=: 0.118 + 0.475 + 0.515
=: 1.108 W
The above power dissipation figures for the TPC8102 are satisfied with ample margin at 2.4 W (Ta = +25 °C) .
CH2
Input voltage VIN (Max) = 19 V output voltage VO = 3.3 V, drain current ID = 3 A, Oscillation frequency
fOSC = 500 kHz, L = 15 µH, drain-source on resistance RDS (ON) =: 50 mΩ, tr = tf=: 100 ns.
Drain current (Max) : ID (Max)
VIN − VO
ID (Max) = IO +
ton
2L
19 − 3.3
2 × 15 × 10−6
1
= 3 +
×
× 0.174
500 × 103
=: 3.18 (A)
Drain current (Min) : ID (Min)
VIN − VO
ID (Min) = IO −
ton
2L
19 − 3.3
2 × 15 × 10−6
1
= 3 −
×
× 0.174
500 × 103
=: 2.82 (A)
25
FUJITSU [ FUJITSU ]
