MB39A119 Datasheet, PDF (15/53 Pages) Fujitsu Component Limited. – DC/DC Converter IC of Synchronous Rectification for charging Li-ion battery

MB39A119
■ FUNCTION DESCRIPTION
1. DC/DC Converter Block
(1) Reference voltage block (REF)
The reference voltage circuit uses the voltage supplied from the VCC terminal (pin 1) to generate a temperature
compensated, stable voltage (5.0 V Typ) used as the reference power supply voltage for the IC’s internal circuitry.
This block can also be used to obtain a load current to a maximum of 1 mA from the reference voltage VREF
terminal (pin 19) .
(2) Triangular wave oscillator block (OSC)
The triangular wave oscillator block has built-in capacitor for frequency setting and generates the triangular wave
oscillation waveform by connecting the triangular wave oscillation frequency setting resistor with the RT terminal
(pin 17) .
The triangular wave is input to the PWM comparator circuits on the IC.
(3) Error amplifier block (Error Amp1)
This amplifier detects the output signal from the current detection amplifier (Current Amp1) , compares this to
the +INE1 terminal (pin 7) , and outputs a PWM control signal to be used in controlling the charge current.
In addition, an arbitrary loop gain can be set up by connecting a feedback resistor and capacitor between the
FB123 terminal (pin 14) and -INE1 terminal (pin 8) , providing stable phase compensation to the system.
(4) Error amplifier block (Error Amp2)
This amplifier detects the output signal from the current detection amplifier (Current Amp2) , compares this to
the +INE2 terminal (pin 12) , and outputs a PWM control signal to be used in controlling the charge current.
In addition, an arbitrary loop gain can be set up by connecting a feedback resistor and capacitor between the
FB123 terminal (pin 14) and -INE2 terminal (pin 13) , providing stable phase compensation to the system.
(5) Error amplifier block (Error Amp3)
This error amplifier (Error Amp3) detects the output voltage from the DC/DC converter and outputs the PWM
control signal. External output voltage setting resistors can be connected to the error amplifier inverted input
terminal to set the desired level of output voltage from 1 cell to 4 cells.
In addition, an arbitrary loop gain can be set by connecting a feedback resistor and capacitor from the FB123
terminal (pin 14) to the -INE3 terminal (pin 15) of the error amplifier, enabling stable phase compensation to the
system.
(6) Current detection amplifier block (Current Amp1)
The current detection amplifier (Current Amp1) detects a voltage drop which occurs between both ends of the
output sense resistor (RS2) due to the flow of the AC adapter current, using the +INC1 terminal (pin 3) and -INC1
terminal (pin 2) . The AC adapter current control signal is amplified to 25 times and output to the inverse input
terminal of Error Amp1 through the internal 100 kΩ.
This amplifier cannot use for detecting the charge current.
(7) Current detection amplifier block (Current Amp2)
The current detection amplifier (Current Amp2) detects a voltage drop which occurs between both ends of the
output sense resistor (RS1) due to the flow of the charge current, using the +INC2 terminal (pin 10) and -INC2
terminal (pin 11) . The signal amplified to 24.5 times is output to the OUTC2 terminal (pin 9) .
(8) PWM comparator block (PWM Comp.)
The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty of the error
amplifiers (Error Amp1 to Error Amp3) depending on their output voltage.
The PWM comparator circuit compares with either of low voltages between the triangular wave voltage generated
by the triangular wave oscillator and the error amplifier output voltage, turns on the main side output transistor
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