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Backlight Enable
The INV input on pin 35 of the backlight control connector (J1) directly shuts down the
inverter output.
Table 18. Backlight Enable Specifications.
Description
Input characteristic
State definition
Temperature Considerations
The LC640.480.21-065 display is designed to operate over a wide temperature range. To
accomplish this, the display must be heated at low temperatures and the power level
reduced at high temperatures. At low temperatures, the lamps are heated using nichrome
wires. At high temperatures, the internal temperature is lowered by reducing the
backlight luminance. Two sensors located on the lamp circuit board monitor the internal
temperature. The 996-0406-01 product incorporates a cell heater to warm the AMLCD
cell at cold temperatures.
Luminance Variation Due to Ambient Temperature
Although the inverter features regulated lamp current drive, luminance will vary across
the temperature range due to the characteristics of the CCFL tubes. Lamp luminance
decreases at low temperatures as the mercury condenses out of the gas and it decreases
again at high temperatures as the tube phosphors become less efficient. The
LC640.480.21-065 has been designed to provide peak luminance at normal room
temperatures without using a heater, and at low temperatures with a heater for the CCFL
tubes.
Backlight power consumption decreases as temperatures climb and the working voltage
of the CCFL tubes decreases. The graph in Figure 14 indicates typical performance
across temperatures.
Figure 14. Backlight Power Consumption.
100.00%
90.00%
80.00%
70.00%
60.00%
50.00%
40.00%
30.00%
20.00%
10.00%
0.00%
-60
24
LC640.480.21-065 Operations Manual (OM610-00)
Specification
CMOS logic-compatible; open circuit defaults to high state
INV low state turns backlight off
Luminance vs. Temperature
(steady state luminance, standard luminance mode, display enclosed)
-40
-20
0
TEMPERATURE (°C)
20
40
60
80
100
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