MB39A112 Datasheet, PDF (25/35 Pages) Fujitsu Component Limited. – 3-ch DC/DC Converter IC

MB39A112
• CH2
L ≥ ^{2 (VIN − Vo2)} tON
Io
≥ ^{2 × (12−3.3)}
1
×
1
2350 × 10³
×
0.275
≥ 2.04 µH
• CH3
L≥
2 (VIN − Vo3)
Io
tON
≥
2 × (12 − 5)
0.3
1
× _{2350 × 103}
× 0.417
≥ 8.28 µH
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
TOKO A916CY-2R0M, A916CY-3R3M and A916CY-100M are used. At 2 µH, 3.3 µH and 10 µH, the load current
value under continuous operating conditions is determined by the following formula.
Load current value under continuous operating conditions : Io
Vo
Io ≥
tOFF
2L
Example : Using the A916CY-2R0M
2 µH (allowable tolerance ± 20 %), rated current = 3 A
• CH1
Vo1
Io ≥
tOFF
2L
1.2
≥
2 × 2 × 10^−6
≥ 0.11 A
1
×
× (1 − 0.1)
2350 × 10³
Example : Using the A916CY-3R3M
3.3 µH (allowable tolerance ± 20 %) , rated current = 2.57 A
• CH2
Vo2
Io ≥
tOFF
2L
3.3
≥
2 × 3.3 × 10^−6
≥ 0.15 A
1
×
× (1 − 0.275)
2350 × 10³
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