MB3886 데이터 시트보기 (PDF) - Fujitsu

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MB3886

2-Channel DC/DC Converter IC with Overcurrent Protection Symmetrical-Phase Type

Fujitsu 

MB3886

s SETTING THE TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT

PROTECTION CIRCUIT

Each channel uses the short-circuit detection comparator (SCP Comp.) to always compare the error amplifier’s

output level to the reference voltage.

While the DC/DC converter load conditions are stable on both channels, the short-circuit detection comparator

keeps its output at the “H” level and the CSCP terminal (pin 25) remains at the input standby voltage (VSTB=: 50

mV) .

If a load condition changes rapidly due to a short circuit of the load, causing the output voltage to drop, the short-

circuit detection comparator changes its output to the “L” level. This causes the external short-circuit protection

capacitor Cscp connected to the CSCP terminal to be charged at 10 µA.

Short-circuit detection time : tscp

tscp (s) =: 0.068 × Cscp (µF)

When the capacitor Cscp is charged to the threshold voltage (VTH=: 0.68 V) , the protection circuit sets the latch

and turns off the external FET (setting the dead time to 100%) . At this time, the latch input is closed and the

CSCP terminal is held at the input latch voltage (VI =: 50 mV) . The protection circuit shuts off both channels

even when a short circuit is detected on only either.

s PROCESSING WITHOUT USING THE CSCP TERMINAL

When the timer-latch short-circuit protection circuit is not used, the CSCP terminal (pin 25) should be shorted

to SGND using the shortest possible connection.

6 SGND

CSCP 25

< Operation Without Using the CSCP Terminal >

19

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