FA5540 Fuji Electric holdings CO.,Ltd, FA5540 Datasheet - Page 23

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

Rev.0 July-2007
(4) Operation at overload
■FA5540 (Auto restart type)
If an overload condition continues more than 180ms, switching is forced to shutdown using an internal timer.
In addition the startup circuit is possible to operate within 1440ms from beginning of an overload condition.
If an overload condition continues, switching is done for 180ms and after that Vcc is provided by a startup
circuit for 1260ms and the operation halt condition is maintained.
When 1440ms passes after beginning of an overload condition, a startup circuit stops its operation and Vcc
begins to drop. When Vcc decreases to 9.0V, IC is once reset and restarted. Since then startup and shutdown
are repeated if an overload condition continues. If load returns to normal, IC returns to an ordinary operation.
However, the output voltage must rise up to the setting value within 180ms settled by the timer at the startup.
Timer
output
FB pin
Vcc
Switching
operation
Start up
circuit
Timer
1440ms
180ms
12.4V
10.2V
9.0V
3.3V
Normal load
180ms
180ms
Fig.7 Operation at overload (FA5540)
FA5540/5541/5542
1440ms
23
Over load
Fuji Electric Device Technology
Normal load