BD7690FJ 查看數據表（PDF） - ROHM Semiconductor
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BD7690FJ Datasheet PDF : 26 Pages
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BD7690FJ
(3-4) VS overvoltage gain increase function (Dynamic OVP)
When output voltage rises by startup or a rapid change of the output load, output voltage rises for a long term because a voltage
control loop is slow. VS pin voltage becomes higher than VOVP (2.625V typ.) (equivalent to +5% of output voltage), the error
amplifier increases a gain. By this operation, it reduces ON width of OUT and prevents a long-term rise of the output voltage.
When VS pin voltage decreases under VOVP(2.625V typ.), this operation stops.
(3-5) VS overvoltage protection function (Static OVP)
VS pin rises across VOVP, static OVP acts, and VS pin voltage rises from VOVP1(2.7V typ.), it stops switching immediately.
VS pin voltage under than VOVP2(2.6V typ.), it starts switching. It shows operation in Figure 8.
PFC
Output
VOVP1
VOVP2
VS
OUT
Switching
stop
Figure 8. VS overvoltage protection operation
(4) CS overcurrent detection
In operation, turn OFF of PFC is usually decided in EO pin voltage. However, when CS pin rises than overcurrent detection
voltage (the CS pin threshold voltage) VCS(0.65V typ.), overcurrent protection works. For this protection, OUT pin turn off pulse
by pulse.
The overcurrent protection limits ON width. The PFC voltage is decrease when this OCP works. Please decide RCS value of
PFC so that this protection does not work in rated load with the minimum input voltage at the time of the application design.
Control
Logic
OUT
CS
Over Current
Protection
0.65V
CCS
RCS
Figure 9. CS overcurrent detection
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TSZ02201-0F2F0A200280-1-2
27. Mar. 2017 Rev.002
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