AME9003 Datasheet, PDF (21/39 Pages) Asahi Kasei Microsystems – CCFL Backlight Controller

AME, Inc.
AME9003
Preliminary
CCFL Backlight Controller
Figure 12. Duty Cycle Dimming
Outside Chip
Inside Chip
BRPOL
Brightness
control
voltage
BRIGHT
CT1
C4
+
-
+
3V ^-
-
50mV ⁺
CHOP
CHOP causes the CCFL to turn on and off
periodically by charging and discharging
SSV. SSV, in turn, pulls the COMP pin low,
periodically turning off the CCFL.
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)
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