MB39A119 Datasheet, PDF (19/53 Pages) Fujitsu Component Limited. – DC/DC Converter IC of Synchronous Rectification for charging Li-ion battery

MB39A119
■ CONSTANT CHARGING VOLTAGE AND CURRENT OPERATION
The MB39A119 is DC/DC converter IC with the pulse width modulation method (PWM method) .
In the output voltage control loop, the output voltage of the DC/DC converter is detected, and the Error Amp3
compares internal reference voltage 4.2 V and DC/DC converter output to output the PWM controlled signal.
In the charging current control loop, the voltage drop generated at both ends of charging current sense resistor
(RS1) is sensed by +INC2 terminal (pin 10) , -INC2 terminal (pin 11) of Current Amp2, and the signal is output
to OUTC2 terminal (pin 9) , which is amplified by 24.5 times. Error Amp2 compares the OUTC2 terminal (pin 9)
voltage, which is the output of Current Amp2, and +INE2 terminal (pin 12) to output the PWM control signal,
and it regulates the charging current.
In AC adapter current control loop, the voltage drop generated at both ends of AC adapter current sense resistor
(RS2) is sensed by +INC1 terminal (pin 3) , -INC1 terminal (pin 2) of Current Amp1, and the signal is output to
-INE1 terminal (pin 8) , which is amplified by 25 times. Error Amp1 compares -INE1 terminal (pin 8) voltage,
which is output of Current Amp1, and +INE1 terminal (pin 7) to output PWM controlled signal, and it limits the
charging current due to the AC adapter current not to exceed the setting value.
The PWM comparator compares the triangular wave to the smallest terminal voltage among the Error Amplifier
output voltage (Error Amp1 to Error Amp3) . And the triangular wave voltage generated by the triangular wave
oscillator. When the triangular wave voltage is smaller than the error amplifier output voltage, the main side
output transistor is turned on and the synchronous rectification side output transistor is turned off.
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