MB3882 Datasheet, PDF (14/30 Pages) Fujitsu Component Limited. – 2-channel DC/DC Converter IC with Synchronous Rectifier

MB3882
2. Channel Control Functions
Channel ON/OFF control is provided by using the CS1 terminal (pin 4) and CS2 terminal (pin 21) setting functions.
Channel On/Off Setting Functions
CS terminal voltage level
Channel output state
CS1
CS2
CH1
CH2
GND
GND
OFF
OFF
GND
Hi-Z
OFF
ON
Hi-Z
GND
ON
OFF
Hi-Z
Hi-Z
ON
ON
3. Protective Functions
(1) Timer Latch Short Circuit Protection (SCP)
The short circuit protection comparators read the output voltage levels. If the output voltage on either channel
falls below the short detection voltage, the timer circuit is activated to start charging the external capacitor Cscp
connected to the CSCP terminal (pin 22) .
When capacitor voltage reaches approximately 0.68 V the output FET turns off, setting the idle interval to 100%.
Once the protection circuit is activated, it can be reset by turning the power supply off and on again. (See “Setting
the Timer Latch Short Circuit Protector Time Constant.”)
(2) Undervoltage Lockout Circuit Block (UVLO)
Transient status during normal power-on or momentary drops in supply voltage can cause abnormal operation
in an control IC, leading to damage or degradation of system components. The undervoltage lockout circuit
prevents such abnormal operations by reading the internal reference voltage level and switching the output
transistor off, setting the idle interval to 100% and holding the CSCP terminal (pin 22) to “L” level.
System operation is restored when the supply voltage rises back about the undervoltage lockout circuit threshold
voltage.
(3) Overvoltage Protection Block (OVP)
The overvoltage protection circuit uses an overvoltage comparator (OVP Comp.) on each channel to read the
output voltage levels from the DC/DC converter. If the output voltage exceeds the threshold voltage a latch is
set, turning off the main side FET on the corresponding channel.
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