MB3832APFV(1999) 데이터 시트보기 (PDF) - Fujitsu
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MB3832APFV Datasheet PDF : 23 Pages
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MB3832A
s FUNCTIONAL DESCRIPTION
1. Switching Regulator Functions
(1) Reference voltage circuit (Ref)
The reference voltage generator uses the voltage supplied from the VCC pin (pin 18) to generate a temperature-
compensated, stable voltage (about 2.50 V) as the reference supply voltage for the IC’s internal circuitry.
The reference voltage can be output, up to 1 mA, to an external device through the VREF pin (pin 1).
(2) Triangular wave oscillator (OSC)
The triangular wave oscillator generates a triangular waveform with a timing capacitor and a timing resistor
respectively connected to the CT pin (pin 3) and RT pin (pin 2).
The triangular wave is input to the PWM comparator in the IC while it can also be supplied to an external device
through the CT pin. In addition, the oscillator can be used for external synchronization, where it generates a
triangular wave synchronous to the input signal from the SYNC pin (pin 4).
(3) Error amplifiers (Error Amp. 1, 2)
The error amplifiers detect the output voltage from the switching regulator and outputs the PWM control signal.
It supports a wide range of in-phase inputs from 0 V to “VCC – 0.9 V”. An arbitrary loop gain can be set by
connecting a feedback resistor and capacitor from the FB1 pin (pin 6) [FB2 pin (pin 15)] to the –IN1 pin (pin 7)
[–IN2 pin (pin 14)] of the error amplifier, enabling stable phase compensation to the system.
(4) Current detector amplifier (Current Amp.)
The current detector amplifier provides 25 × amplification of the voltage drop between the two ends of the
output sensor resistor (RS) in the switching regulator, that occurs due to the flow of the charging current. At
the same time, the amplifier converts the voltage to the GND-reference voltage level and outputs it to the COUT
pin (pin 12). It can also control the charging current in combination with the error amplifier circuit.
(5) Power control circuit (CTL)
The power control circuit can control turning on and off the power supply through the CTL pin (pin 17). (Supply
current in standby mode: About 0 µA)
Depending on the voltage level of the PWM Comp. input pin, the OUT pin (pin 19) may become “L” level during
discharging of the VREF voltage after the CTL pin is turned off with a capacitor connected to the VREF pin. The
power control circuit contains a function for fixing the OUT output pin to the “H” level when CTL = “L” and VREF
= “H”, preventing inadvertent “L” level output after turning the CTL pin off.
(6) PWM comparator circuit (PWM Comp.)
The PWM comparator circuit is a voltage-pulse width converter for controlling the output duty of the error
amplifiers (Error Amp. 1, 2) depending on their output voltage.
The PWM comparator circuit turns on the external output transistor during the interval in which the triangular
wave voltage level is lower than the voltage level at both of the error amplifier output pins (FB1 pin (pin 6), FB2
pin (pin 15)) and the DTC pin (pin 16).
(7) Output circuit (Out)
The output circuit uses a totem-pole configuration, capable of driving an external P-channel MOS FET and
PNP transistor. It can also control the output sink current with a resistor connected between the VE pin
(pin 20) and the GND pin (pin 11).
2. Protection Functions
(1) Low input voltage malfunction preventive circuit (ULVO)
The transient state or a momentary decrease in supply voltage, which occurs when the power supply is turned
on, may cause errors in the control IC, resulting in breakdown or degradation of the system. The low input
voltage malfunction preventive circuit detects the internal reference voltage level according to the supply voltage
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