MB39A125 Datasheet, PDF (55/64 Pages) Fujitsu Component Limited. – DC/DC Converter IC for Charging Li-ion Battery

MB39A125/126
12.6 V output
Vo
IDi ≥ Io × (1 −
)
VIN
≥ 3 × (1 − 0.572)
≥ 1.284 A
16.8 V output
IDip ≥ (Io +
≥ 3.6 A
Vo
tOFF)
2L
12.6 V output
IDip ≥ (Io +
≥ 3.6 A
Vo
tOFF)
2L
• Charge current sense resistor
Please note the following in selecting the charge current sense resistance. First of all, meet the electric power
to the flowing current. However, the conversion efficiency deteriorates because the loss in the sense resistance
grows when resistance is adjusted to a too big value. The accuracy of the charge current deteriorates because
the voltage difference of both ends of the sense resistance becomes small when resistance is adjusted to a too
small value oppositely. 33 mΩ of the KOA SL1TTE33LOF is used in this application. The sense resistance value
can be determined by the following formulas.
In this application, 33 mΩ of the KOA SL1TTE33LOF is used.
Sense resistor : RS2
+INE1
RS2 =
20 × Io
Example) When the +INE1 terminal (pin 9) voltage is 2 V and the charge current (Io) is 3.0 A
+INE1
RS2 =
20 × Io
2
=
20 × 3.0
= 33.3 mΩ
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