Magnum PF21GB300 Service Manual page 19

4.5 SWITCH-MODE POWER SUPPLY IC FSCQ0765RT
Pin Number Pin Name
1 Drain
2 GND
3 Vcc
4 Vfb
5 Sync
Internal Block Diagram
Pin Function Description
High voltage power SenseFET drain connection.
This pin is the control ground and the SenseFET source.
This pin is the positive supply input. This pin provides internal
operating current for both start-up and steady-state operation.
This pin is internally connected to the inverting input of the PWM
comparator. The collector of an opto-coupler is typically tied to this
pin. For stable operation, a capacitor should be placed between this pin
and GND. If the voltage of this pin reaches 7.5V, the over load protection
triggers, which results in the FPS shutting down.
This pin is internally connected to the sync detect comparator for
quasi-resonant switching. In normal quasi-resonant operation, the
threshold of the sync comparator is 4.6V/2.6V. Whereas, the sync threshold
is changed to 3.0V/1.8V in an extended quasi-resonant operation.
19