mb3883pv Fujitsu Microelectronics, Inc., mb3883pv Datasheet - Page 19

• Manufacturer Part Number: mb3883pv
• Description: 6-ch Dc/dc Converter Ic With Synchronous Rectification For Voltage Step-up And Step-down
• Manufacturer: Fujitsu Microelectronics, Inc.

2. Channel Control Function
3. Protective Functions
(1) Timer-latch short-circuit protection circuit
(2) Undervoltage lockout protection circuit
(3) Output switch control circuit
CTL
Channels are turned on and off depending on the voltage levels at the CTL terminal (pin 20), CTL1, 2 terminal
(pin 21), CTL3 terminal (pin 22), CTL4 terminal (pin 23), and CTL5 terminal (pin 24).
The short-circuit detection comparator in each channel detects the output voltage level and, if any channel output
voltage falls below the short-circuit detection voltage, the timer circuits is actuated to start charging the external
capacitor C
When the capacitor voltage reaches about 0.70 V, the circuit is turned off the output transistor and sets the dead
time to 100 %.
To reset the actuated protection circuit, turn the power supply on back. (See “SETTING TIME CONSTANT FOR
TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT”.)
The transient state or a momentary decrease in supply voltage, which occurs when the power supply is turned
on, may cause the IC to malfunction, resulting in breakdown or degradation of the system. To prevent such
malfunctions, the undervoltage lockout protection circuit detects a decrease in internal reference voltage with
respect to the power supply voltage, turns off the output transistor, and sets the dead time to 100% while holding
the CSCP terminal (pin 18) at the “L” level.
The circuit restores the output transistor to normal when the supply voltage reaches the threshold voltage of the
undervoltage lockout protection circuit.
When the power is turned on, this circuit prevents reactive current flow to external step-up circuits on CH5 and
CH6. When the SWIN terminal (pin 2) is a state at “H” level after releasing UVLO and the C+IN6 terminal (pin5)
voltage goes above 0.9 V (Typ.), the SWOUT terminal (pin 1) becomes “L” level. External P-ch MOS FET is
turned on at this time and the output voltage is generated.
H
L
: Undefined
CTL1, 2
Voltage level at CTL pin
SCP
H
L
connected to the CSCP terminal (pin 18).
CTL3
H
H
L
L
CTL4
H
H
H
H
L
L
L
L
Channel On/Off Setting Conditions
CTL5
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
Power/CH6
ON
CH1, CH2
OFF
Channel on/off state
ON
OFF (Standby state)
CH3
OFF
OFF
ON
ON
CH4
OFF
OFF
OFF
OFF
ON
ON
ON
ON
MB3883
CH5
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
ON
ON
ON
19