FSCQ-SERIES
Internal Block Diagram
Sync
5
Vcc
3
Drain
1
+
-
Quasi-Resonant
(QR) Switching
Controller
+
-
fs
Threshold
9V/15V
Soft Start
4.6V/2.6V : Normal QR
3.0V/1.8V : Extended QR
Vcc good
Auxiliary
Burst Mode
Controller
OSC
Vref
Main Bias
VBurst
Normal Operation
Burst Switching
Normal
Internal
Bias
Vref
IBFB
Vref
IFB
Vref
IB
Operation
Vcc
Idelay
PWM
VFB
S
Q
Q
4
2.5R
Gate
Driver
R
R
LEB
600ns
VSD
Sync
S
Q
AOCP
Q
Q
S
Vovp
Vcc good
(Vcc = 9V)
R
Q
2
GND
R
TSD
Vocp
Power Off Reset (Vcc = 6V)
Figure 2. Functional Block Diagram of FSCQ-Series
2