FA5540 Fuji Electric holdings CO.,Ltd, FA5540 Datasheet - Page 21

• Manufacturer Part Number: FA5540
• Description: Fuji Switching Power Supply Control Ic
• Manufacturer: Fuji Electric holdings CO.,Ltd

Rev.0 July-2007
contrary when FB pin voltage rises higher than the pulse shutdown threshold voltage, switching is started
again. FB pin voltage overshoots and undershoots centering around the pulse shutdown threshold voltage for
mode change. Continuous pulse is output during the overshoot period and long period burst frequency is
obtained during the undershoot period.
When FB pin voltage drops lower than the pulse shutdown threshold voltage, switching is shut down. On the
(2) Burst operation at light load
FB pin
Voltage
Pulse stop
voltage
VTHFB0
OUT pin
Switching
pulse
Heavy load
Light load (burst switching)
Fig.4 Burst operation at light load
FA5540/5541/5542
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Fuji Electric Device Technology