MB39A125 Datasheet, PDF (56/64 Pages) Fujitsu Component Limited. – DC/DC Converter IC for Charging Li-ion Battery

MB39A125/126
• Input current sense resistor
Please note the following in selecting the input 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 input 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, 15 mΩ of the KOA SL1TTE15LOF is used.
Sense resistor : RS1
+INE2
RS1 =
20 × IIN
Example) When the +INE2 terminal (pin 3) voltage is 1.79 V and the input current (IIN) is 6.0 A
RS1
+INE2
=
20 × IIN
1.79
=
20 × 6.0
= 14.9 mΩ
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