MB39A125 Datasheet, PDF (52/64 Pages) Fujitsu Component Limited. – DC/DC Converter IC for Charging Li-ion Battery

MB39A125/126
Inductance value : L
2 (VIN − Vo)
L≥
tON
Io
16.8 V output
Example)
2 (VIN (Max) − Vo)
L≥
tON
Io
2 × (25 − 16.8)
1
≥
×
× 0.672
3
300 × 10³
≥ 12.2 µH
12.6 V output
Example)
2 (VIN (Max) − Vo)
L≥
tON
Io
2 × (22 − 12.6)
1
≥
×
× 0.572
3
300 × 10³
≥ 12.0 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
SUMIDA CDRH104R-150 is used. The following formula is available to obtain the load current as a continuous
current condition when 15 µH is used.
The value of the load current satisfying the continuous current condition : Io
Vo
Io ≥
tOFF
2L
Example) Using the CDRH104R-150
15 µH (tolerance ± 30%) , rated current = 3.6 A
16.8 V output
Vo
Io ≥
tOFF
2L
16.8
1
≥
×
× (1 − 0.672)
2 × 15 × 10^−6
300 × 10³
≥ 0.61 A
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