MB39A132QN-G-ERE1 Datasheet, PDF (17/56 Pages) Fujitsu Component Limited. – ASSP For Power Management Applications (Rechargeable Battery) Synchronous Rectification DC/DC Converter IC for Charging Li-ion Battery

MB39A132
1. Blocks of DC/DC Converter
(1) Reference voltage block (REF)
The reference voltage circuit uses the voltage supplied from the VCC pin (pin 1) to generate stable voltage
(Typ. 5.0 V) that has undergone temperature compensation. The generated voltage is used as the reference
power supply for the internal circuitry of the IC.
This block can output load current of up to 1 mA from the reference voltage VREF pin (pin 21).
(2) Triangular wave oscillator block (OSC)
The triangular wave oscillator builds the capacitor for frequency setting into, and generates the triangular
wave oscillation waveform by connecting the frequency setting resistor with the RT pin (pin 20).
The triangular wave is input to the PWM comparator on the IC.
Triangular wave oscillation frequency: fosc
fosc (kHz) =: 17000/RT (kΩ)
(3) Error amplifier block (Error Amp1)
This amplifier detects the output signal from the current detection amplifier (Current Amp1) and outputs a
PWM control signal.
In addition, a stable phase compensation can be made available to the system by connecting the resistor
and the capacitor to the COMP1 pin (pin 8).
(4) Error amplifier block (Error Amp2)
This amplifier detects the output signal from the current detection amplifier (Current Amp2), compares this
to the output signal from the charge current control circuit, and outputs a PWM control signal to be used in
controlling the charge current.
In addition, a stable phase compensation can be made available to the system by connecting the resistor
and the capacitor to the COMP2 pin (pin 15).
(5) Error amplifier block (Error Amp3)
This error amplifier (Error Amp3) detects the output voltage from the DC/DC converter, compares this to the
output signal from the VO REFIN controller circuit, and outputs the PWM control signal. Arbitrary output
voltage from 2 Cell to 4 Cell can be set by connecting an external resistor of charging voltage to ADJ3 pin
(pin 18).
In addition, a stable phase compensation can be made available to the system by connecting the resistor
and the capacitor to the COMP3 pin (pin 16).
(6) Current detection amplifier block (Current Amp1)
The current detection amplifier (Current Amp1) amplifies the voltage difference between the +INC1 pin (pin
3) and the -INC1 pin (pin 2) by 25 times and outputs the amplified signal to the OUTC1 pin (pin 10).
(7) Current detection amplifier block (Current Amp2)
The current detection amplifier (Current Amp2) detects a voltage drop occurring at both ends of the charge
current sense resistor (Rs) with the +INC2 pin (pin 12) and the -INC2 pin (pin 13). It outputs the signal
amplified by 25 times to the inverted input pin of the following error amplifier (Error Amp2) and to the OUTC2
pin (pin 11).
(8) PWM comparator block (PWM Comp.)
The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty according to
the output voltage of the error amplifiers (Error Amp1 to Error Amp3).
The triangular wave voltage generated by the triangular wave oscillator is compared with the output voltage
of one of the three error amplifiers (Error Amp1, Error Amp2 and Error Amp3) that has the lowest potential.
The main FET is turned on during the period when the triangular wave voltage is lower than the error amplifier
output voltage.
(9) Output block (OUT)
The output block uses a CMOS configuration on both the high-side and the low-side, and can drive the
external N-ch MOS FET.
DS04–27265–3E
17