MB3883 Datasheet, PDF (26/39 Pages) Fujitsu Component Limited. – 6-ch DC/DC Converter IC With Synchronous Rectification for voltage step-up and step-down

MB3883
s SETTING TIME CONSTANT FOR TIMER-LATCH SHORT-CIRCUIT PROTECTION CIRCUIT
The short detection comparator (SCP comparator) in each channel monitors the output voltage.
While the switching regulator load conditions are stable on all channels, the LOG_SCP output remains at “H”
level, transistor Q1 is turned on, and the CSCP terminal (pin 18) is held at “L” level.
If the load condition on a channel changes rapidly due to a short of the load, causing the output voltage to drop,
the output of the short detection comparator on that channel goes to “H” level. This causes transistor Q1 to be
turned off and the external short protection capacitor CSCP connected to the CSCP terminal to be charged at 1.0
µA.
Short detection time (tPE)
tPE (s) =: 0.70 × CSCP (µF)
When the capacitor CSCP is charged to the threshold voltage (VTH =: 0.70 V), the latch is set and the external
FET is turned off (dead time is set to 100%). At this point, the latch input is closed and the CSCP terminal is
held at “L” level.
A
R1
34
−IN1
R2
1.0 V
SCP
− ^Comp.1
+
External FET
Drive
1−1
Drive
1−2
37
OUT1−1
38
OUT1−2
0.9 V
CSCP
18
1 µA
CSCP
Q1
SCP
− Comp.6
+
LOG_SCP
bias
S
R
Timer-latch short
protection circuit
UVLO
Drive
6
bias
47
OUT6
Ref
Power
ON/OFF CTL
20
CTL
Timer-latch short circuit protection circuit
26