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MB39A104
25
The above power dissipation figures for the TPC8102 are satisfied with ample margin at 2.4 W (Ta = +25 °C) .
CH2
Input voltage V
IN (Max) = 19 V output voltage VO = 3.3 V, drain current ID = 3 A, Oscillation frequency
f
OSC = 500 kHz, L = 15 µH, drain-source on resistance RDS (ON) := 50 mΩ, tr = tf := 100 ns.
Drain current (Max) : I
D (Max)
Drain current (Min) : ID (Min)
PC = ID
2
× RDS (ON) × Duty
= 3
2
× 0.05 × 0.263
:= 0.
118 W
PS (ON) =
VD (Max) × ID × tr × fOSC
6
=
19 × 3 × 100 × 10
−9
× 500 × 10
3
6
:= 0.475
W
PS (OFF) =
VD (Max) × ID (Max) × tf × fOSC
6
=
19 × 3.25 × 100 × 10
−9
× 500 × 10
3
6
:= 0.515
W
PT = PC + PS (ON) + PS (OFF)
:= 0.118 + 0.475 + 0.515
:= 1.
108 W
ID (Max) = IO +
VIN − VO
ton
2L
= 3 +
19 − 3.3
×
1
× 0.174
2 × 15 × 10
−6
500 × 10
3
:= 3.18 (A)
ID (Min) = IO −
VIN − VO
ton
2L
= 3 −
19 − 3.3
×
1
× 0.174
2 × 15 × 10
−6
500 × 10
3
:= 2.82 (A)