Data Sheet

© 2006 Fairchild Semiconductor Corporation www.fairchildsemi.com
FSQ-Series • Rev. 1.1.3 4
FSCQ-Series — Green Mode Fairchild Power Switch (FPS™)
Pin Configuration
5
SYNC
4
VFB
3
VCC
2
GND
1
DRAIN
Figure 3. Pin Assignments (Top View)
Pin Descriptions
Pin
Name
Description
1
DRAIN
This pin is the high-voltage power SenseFET drain connection.
2
GND
This pin is the control ground and the SenseFET source.
3
VCC
This pin is the positive supply input. This pin provides internal operating current for both startup
and steady-state operation.
4
VFB
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 7.5 V, the overload protection
triggers, which results in the FPS™ shutting down.
5
SYNC
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 4.6 V / 2.6 V. Whereas,
the sync threshold is changed to 3.0 V / 1.8 V in an extended quasi-resonant operation.