MB39A112 Datasheet, PDF (23/35 Pages) Fujitsu Component Limited. – 3-ch DC/DC Converter IC

MB39A112
PS (ON) =
=
=:
VD × ID × tr × fosc
6
12 × 1 × 2.9 × 10^−9 × 2350 × 10³
6
0.0136 W
PS (OFF) =
VD × ID (Max) × tf × fosc
6
12 × 1.15 × 8.7 × 10^−9 × 2350 × 10³
=
6
=: 0.047 W
PT = PC + PS (ON) + PS (OFF)
=: 0.0495 + 0.0136 + 0.047
=: 0.11 W
The above power dissipation figures for the MCH3312 are satisfied with ample margin at 1.0 W (Ta = +25 °C) .
Example : Using the MCH3308
• CH3
Input voltage VIN = 12 V, output voltage Vo = 5.0 V, drain current ID = 0.3 A, oscillation frequency fosc =
2350 kHz, L = 10 µH, drain-source on resistance RDS (ON) =: 600 mΩ, tr =: 4 ns, tf =: 4 ns.
Drain current (Max) : ID (Max)
ID (Max) = Io +
VIN − Vo
tON
2L
= 0.3 +
12 − 5
2 × 10 × 10^−6
=: 0.36 (A)
1
×
× 0.417
2350 × 10³
Drain current (Min) : ID (Min)
ID (Min) = Io −
VIN − Vo
tON
2L
= 0.3 −
12 − 5
2 × 10 × 10^−6
=: 0.24 (A)
1
×
×
2350 × 10³
0.417
PC = ID2 × RDS (ON) × Duty
= 0.3² × 0.6 × 0.417
=: 0.023 W
23