Figure 3. Pin Configuration (Top View)
Pin # Name
SenseFET Drain. High-voltage power SenseFET drain connection.
Ground. This pin is the control ground and the SenseFET source.
Power Supply. This pin is the positive supply input, providing internal operating current for
both startup and steady-state operation.
Feedback. 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 6V, the overload pro-
tection triggers, which shuts down the FPS.
Sync. This pin is internally connected to the sync-detect comparator for quasi-resonant switch-
ing. In normal quasi-resonant operation, the threshold of the sync comparator is 1.2V/1.0V.
Startup. This pin is connected directly, or through a resistor, to the high-voltage DC link. At
startup, the internal high-voltage current source supplies internal bias and charges the exter-
nal capacitor connected to the VCC pin. Once VCC reaches 12V, the internal current source is
disabled. It is not recommended to connect Vstr and Drain together.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1