MB3882 Datasheet, PDF (15/30 Pages) Fujitsu Component Limited. – 2-channel DC/DC Converter IC with Synchronous Rectifier

MB3882
s SETTING THE TIMER LATCH SHORT CIRCUIT PROTECTOR TIME CONSTANT
Each channel has a short circuit protection comparator (SCP Comp.) which constantly compares the error Amp.
output level to the reference voltage.
When the DC/DC comparator load conditions are stable on all channels, the short circuit protection comparator
output is at “H” level, transistor Q1 is on, and the CSCP terminal (pin 22) is held at input standby voltage
(VSTB : = 50 mV) .
If load conditions change rapidly, such as during a load short, causing output voltage to drop, the short circuit
protection comparator output goes to “L” level. This causes the transistor Q1 to shut off, charging the short circuit
protection capacitor Cscp (connected to the CSCP terminal) at 1 µA.
Short detection time
tscp (s) =: 0.68 × Cscp (µF)
When the capacitor Cscp is charted to the threshold voltage (VTH : = 0.68 V) a latch is set, turning the external
FET off (setting the idle interval to 100%) . At this time the latch input is closed and the CSCP terminal is held
at the input latch voltage (VI : = 50 mV) . (When a short circuit is detected on either of the two channels, both
channels are shut off.)
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