MB3888 Fuji Electric, MB3888 Datasheet - Page 15

• Manufacturer Part Number: MB3888
• Description: DC/DC Converter IC for Charging Li-ion Battery
• Manufacturer: Fuji Electric

CTL function table
2. Protection Functions
Under voltage lockout protection circuit (UVLO)
Protection function (UVLO) operation table
3. Soft-Start Function
Soft-start block (SOFT)
(7) Output block (OUT)
(8) Control block (CTL)
(9) Bias voltage block (VH)
The PWM comparator circuit compares the triangular wave generated by the triangular wave oscillator to the
error amplifier output voltage or DTC terminal 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.
The output circuit uses a totem-pole configuration capable of driving an external P-channel 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.
Setting the CTL terminal (pin 3) at “L” level places the IC in the standby mode. (The supply current is 10 A at
maximum in the standby mode.) Setting the CTL terminal at “H” level generates an internal reference voltage,
placing the system under outputting status.
The bias voltage circuit outputs V
mode, this circuit outputs the potential equal to V
The transient state or a momentary decrease in supply voltage or internal reference voltage (VREF) , which
occurs when the power supply (VCC) is turned on, may cause malfunctions in the control IC, resulting in
breakdown or degradation of the system.
To prevent such malfunction, the under voltage lockout protection circuit detects a supply voltage or internal
reference voltage drop and fixes the OUT terminal (pin 18) to the “H” level. The system restores voltage supply
when the supply voltage or internal reference voltage reaches the threshold voltage of the under voltage lockout
protection circuit.
When UVLO is operating (VCC or VREF voltage is lower than UVLO threshold voltage) .
Connecting a capacitor to the CS terminal (pin 20) prevents surge currents when the IC is turned on. Using an
error amplifier for soft-start detection makes the soft-start time constant, being independent of the output load
of the DC/DC converter.
OUTD
CTL
Hi-Z
H
L
CC
6 V (Typ) as the minimum potential of the output circuit. In the standby
OFF (Standby)
ON (Active)
Power
OUT
CC
H
.
OUTD
Hi-Z
CS
L
L
MB3888
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