AME9002 Datasheet, PDF (20/37 Pages) Asahi Kasei Microsystems – CCFL Backlight Controller

AME, Inc.
AME9002
Preliminary
Figure 12. Duty Cycle Dimming
CCFL Backlight Controller
Outside Chip
Inside Chip
BRPOL
Brightness
control
voltage
BRIGHT
CT1
C4
+
-
+
3V ^-
-
50mV ⁺
CHOP
CHOP causes the CCFL
to turn on and off
periodically.
S
Q
R
Figure 13. Alternative Brightness Control
Inside Chip Outside Chip
CHOP
Always Hi
BRPOL
T1
BRIGHT
5V
CT
-
To PWM
Comparator
To Fault
Control Logic
EA1
-
+
-
COMP
FB
2.5V
CSDET
1.25V
RF
R-C-D
optional
network
R₂
R₁
2R
R
This method disables
duty cycle dimming
Maximum current=
K
R₁//(2R+R)
Minimum current=
K
(R₁+R₂)//(2R+R)
20