MB3873 Datasheet, PDF (13/22 Pages) Fujitsu Component Limited. – Multi-Resonance AC/DC Converter IC

MB3873
s SETTING THE SOFT START TIME
When the MB3873 is started, the soft start capacitor (Cs) connected to the CS terminal begins charging. While
the CS terminal voltage is =: 0 to 1.1V, the oscillator frequency is controlled by the CS terminal voltage, thereby
controlling the output voltage.
The soft start capacitor charging current is as follows
ICS1 =: 25 µA (CS pin voltage =: 0 to 1.1V)
ICS2 =: 2.5 µA (CS pin voltage =: 1.1 to 3.1V (CS pin clamp voltage))
Soft start time (time until CS pin voltage reaches 1.1V)
tCS
[s]
=:
1.2 ×
25
CS [µF]
[µA]
s SETTNG THE OVERLOAD DETECTION DELAY TIME
When an overload condition is detected, the delay capacitor (CD) connected to the CD terminal starts charging
( =: 10 µA), increasing the CD terminal voltage.
When the CD terminal voltage exceeds the threshold voltage ( =: 4V), the error detection latch is set, and the
VREF terminal (pin 10) and OUT terminal (pin 8) are set to “L” level.
Overload detection delay time (time from overload detection until error latch is set)
tCS [s] =:
3.9 × CD [µF]
10 [µA]
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