Akai LCT3285TAJ, Service Manual, Page: 88 / 131

condition at Ta = 25
±
2
℃
and I
L
= 4.0 ~ 5.0 mA
RMS
.
Note (5) The power supply capacity should be higher than the total inverter power consumption P
BL
. Since
the pulse width modulation (PWM) mode was applied for backlight dimming, the driving current
changed as PWM duty on and off. The transient response of power supply should be considered
for the changing loading when inverter dimming.
Note (6) To enhance the performance of backlight, the power consumption will increase to 1.5 times of the
typical power consumption P
BL
in the power on stage and 20 seconds later it will return to typical
value. Thus, the power source capacity for inverter should be considered to supply the initial
power consumption at power on duration.
3.2.3 INVERTER INTERFACE CHARACTERISTICS
Value
Parameter Symbol
Test
Condition
Min. Typ. Max.
Unit Note
ON
－
2.0
－
5.0 V On/Off Control
Voltage
OFF
V
BLON
－
0
－
0.8 V
HI
－
2.0
－
5.0 V Internal/External
PWM Select Voltage LO
V
SEL
－
0
－
0.8 V
MAX
－ －
3.0 V minimum duty ratio Internal PWM
Control Voltage
MIN
V
IPWM
V
SEL
= L
－
0
－
V maximum duty ratio
HI 2.0
－
5.0 V duty on External PWM
Control Voltage
LO
V
EPWM
V
SEL
= H
0
－
0.8 V duty fff
Control Signal Rising Time T
r
－ － －
100 ms
Control Signal Falling Time T
f
－ － －
100 ms
PWM Signal Rising Time T
PWMR
－ － －
50 us
PWM Signal Falling Time T
PWMF
－ － －
50 us
Input impedance R
IN
－
1
－ －
M
Ω
BLON Delay Time T
on
－
500
－ －
ms
BLON Off Time T
off
－
500
－ －
ms
Note (1) The SEL signal should be valid before backlight turns on by BLON signal. It is inhibited to change
the internal/external PWM selection (SEL) during backlight turn on period.
Note (2) The power sequence and control signal timing are shown as the following figure.
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