The World Leader in High Performance Signal Processing Solutions ADI Confidential Information ADI Confidential Information – – Not for external distribution Not for external distribution Advanced LED Backlighting Technology Justin Zhao Nov 1st, 2008 Including ALS (ambient light sensing), dimming & fading, fun-lighting, etc.. http://www.elecfans.com 电子发烧友 http://bbs.elecfans.com 电子技术论坛
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The World Leader in High Performance Signal Processing Solutions
ADI Confidential InformationADI Confidential Information –– Not for external distributionNot for external distribution
Advanced LED Backlighting Technology
Justin ZhaoNov 1st, 2008
Including ALS (ambient light sensing), dimming & fading, fun-lighting, etc..
Using a PhotoDiode to measure the Ambient Light ConditionsLight level is used to Dynamically adjust the backlight light intensity to match the ambient light
Higher Backlight Current in Higher Ambient Light Conditions
Some example SettingsOutdoor 16mA (5-6 LEDS)Office 5mADark 1.5mA
Solution 2 : Image Content Based Adaptive Backlight Control (cABC)
90% of Display Power is taken by BacklightCABC looks at video image data and used PWM to reduce backlight based on content. (Darker Images require less backlighting)Average reduction in power is 30%Gamma Compensation of Image Required
Ambient Light Sensor ImplementationsIt is critical to maintaining battery life as backlight + (keypad) usage increases
Method #1 – Manual ☺ Method #2 - ADC
User manually adjusts backlight to level most often used –“office” +must be ok in daylight GPS, Video, Internet = Dangerous, FrustratingHigher IAverage = Less Battery Life
e.g Capella CM3200 Requires Processor polling and ADC (built into processor)Sony Ericsson xxxx, Nokia xxx, xxxx, xxx– Discrete (E.g. Osram SFH3710 Photodiode)
ADP5501 “Glowfish” Ambient Light Sensing Lighting Management System
-40°C to 85°C
TemperatureRange
Vboost: 24VImax : 31mA
(programmable)
Boost
KEY BENEFITSKEY BENEFITSBacklight Driver
24V Low noise 1.5 MHz to 2.5 MHz PWM Boost with selectable opera24V Low noise 1.5 MHz to 2.5 MHz PWM Boost with selectable operating ting frequencyfrequency
BuiltBuilt--in automatic OVP protection with IRQin automatic OVP protection with IRQ93% efficiency, 4.7 uH 93% efficiency, 4.7 uH –– 10 10 μμH selectable power inductor value H selectable power inductor value (selectable via fuse)(selectable via fuse)
Each profile allows customizable: Max current, Dim current, Dim Each profile allows customizable: Max current, Dim current, Dim timeout, Off timeout, timeout, Off timeout, Fade law, FadeFade law, Fade--in time, fade out time in time, fade out time
programmable trip points & hysteresis for profile transitions wiprogrammable trip points & hysteresis for profile transitions with absolutely th absolutely no flickerno flickerII22C override for 100% customization and controlC override for 100% customization and controlAutonomous mode to completely off load processorAutonomous mode to completely off load processor
Push button display & processor wake Push button display & processor wake -- upup
All lighting functions can be handled with 3 lines to the procesAll lighting functions can be handled with 3 lines to the processorsor
Function/PerformanceCharge Pump based WLED DriverTri-Mode Charge Pump for high efficiency30mA Typical LED currentInternal Soft Start, shutdownUVLO, OVP, Thermal ShutdownAutomatic LED disconnect
FeaturesIndependent Current Sink ControlAutomatic Ambient Light Sense Control
Built in comparator with programmable trip points for Dark, Office and Outdoor ModesIndependent LED sinks with programmable blinking and fade features
Parallel LED Configuration ProsNo inductor required – May have less EMI One LED Failure will not disable display5V Process may allow for lower cost, integration into PMUSmaller, Lower Profile Solution
0.5mm Height
Series LED Configuration ProsImproved efficiency across Li-Ion Battery RangeCurrent Matching not an issueInductor size and cost reducing
ADP5520 – ALS Backlight Driver with I/O Port ExpanderKEY FEATURESKEY FEATURESBackl
Customiza
Configurable Port Expander
RGB/In
State Machi
ight DriverNonNon--synchronous boost converter operating at 85% efficiencysynchronous boost converter operating at 85% efficiencyDrive up to 6 white Drive up to 6 white LEDsLEDs in seriesin series
ble Ambient Light Management SystemLED current control via a programmable current sink (128 levels LED current control via a programmable current sink (128 levels between 0 and 30mA)between 0 and 30mA)Programmable backlight fade in/out, dim and off timersProgrammable backlight fade in/out, dim and off timersAmbient light sensor for automatic backlight adjustmentAmbient light sensor for automatic backlight adjustment
8 configurable GPIO pins (input, output, up to 4x4 keypad matrix8 configurable GPIO pins (input, output, up to 4x4 keypad matrix))
dicator LED ControllersUp to 3 auxiliary LED current sinks (64 levels between 0 and 15mUp to 3 auxiliary LED current sinks (64 levels between 0 and 15mA)A)Programmable auxiliary LED fade in/out timersProgrammable auxiliary LED fade in/out timersProgrammable auxiliary LED on/off timers (allows blinking)Programmable auxiliary LED on/off timers (allows blinking)
neII22C compatible serial interfaceC compatible serial interfaceInterrupt line for signaling an external processorInterrupt line for signaling an external processorCurrent limit, overvoltage & thermal overload protectionCurrent limit, overvoltage & thermal overload protectionHard resetHard reset
Minimizes lines across the hinge Minimizes lines across the hinge Off loads processor functionsOff loads processor functions
&&Reduces system power consumptionReduces system power consumption
Analog Devices, Inc.22/F, One Corporate Avenue222 Hu Bin Road, Shanghai, 200021, ChinaOffice: 86-21-2320-8088Mobile: 86-1376-122-5504EMAIL: [email protected]