MB39A125 Datasheet, PDF (25/64 Pages) Fujitsu Component Limited. – DC/DC Converter IC for Charging Li-ion Battery

MB39A125/126
(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 AC adapter current, using the +INC2 terminal (pin 24) and
−INC2 terminal (pin 1) . The signal amplified to 20 times is output to the OUTC2 terminal (pin 2) .
(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 the triangular wave voltage the lowest generated by the triangular wave
oscillator to the error amplifier output voltage and turns on the external output transistor, during the interval in
which the triangular wave voltage is lower than the error amplifier output voltage.
(9) Output block (OUT)
The output circuit uses a totem-pole configuration capable of driving an external Pch MOS FET.
The output “L” level sets the output amplitude to 6 V (Typ) using the voltage generated by the bias voltage block
(VH) .
This results in increasing conversion efficiency and suppressing the withstand voltage of the connected external
transistor in a wide range of input voltages.
(10) Power supply control block (CTL)
Setting the CTL terminal (pin 14) low places the IC in the standby mode. (The power supply current is 10µA at
maximum in the standby mode.)
CTL function table : MB39A125
CTL
L
H
Power
OFF (Standby)
ON (Active)
OUTD
Hi-Z
L
CTL function table : MB39A126
CTL
L
H
Power
OFF (Standby)
ON (Active)
(11) Bias voltage block (VH)
The bias voltage circuit outputs VCC − 6 V (Typ) as the minimum potential of the output circuit. In the standby
mode, this circuit outputs the potential equal to VCC.
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