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LED Backlight Current Sinks
The backlight current is set via the SemWire interface. The current is regulated to one of 32 values
between 0.5mA and 25mA. The step size varies depending upon the current setting. Between 0.5mA and
12mA, the step size is 0.5mA. The step size increases to 1mA for settings between 12mA and 15mA and
2mA for settings greater than 15mA. This feature allows fi ner adjustment for dimming functions in the
low current setting range and coarse adjustment at higher current settings where small current changes
are not visibly noticeable in LED brightness.
All backlight current sinks have matched currents, even when there is variation in the forward voltages
( VF ) of the LEDs. A VF of 1.2V is supported when the input voltage is at 3.0V. Higher VF LED mis-
match is supported when VIN is higher than 3.0V. All current sink outputs are compared and the lowest
output is used for setting the voltage regulation at the VOUT pin. This is done to ensure that suffi cient
bias exists for all LEDs.
The backlight LEDs default to the off state upon powerup. For backlight applications using less than four
LEDs, any unused output must be left open and the unused LED driver must remain disabled. When
writing to the Backlight Enable Control register, a zero
unused output.
Backlight Quiescent Current
The quiescent current required to operate all four backlights is reduced by 1.5mA when backlight current
is set to 4.0mA or less. This feature results in higher efficiency under light-load conditions. Further
reduction in quiescent current will result from using fewer than four LEDs.
Copyright © 2010 LG Electronics. Inc. All right reserved.
Only for training and service purposes
(0)
must be written to the corresponding bit of any
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3. TECHNICAL BRIEF
3. TECHNICAL BRIEF
LGE Internal Use Only
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