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June 14 - 16, 2009 Introducing LED Backlighting Solutions AC103 Michael Jennings Market Segment Manager – Display Products TM Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Contents ►Target Applications ►LED Backlighting ►LED Advantages ►Technical Challenges ►Advanced Architectures ►Notebook/Medium Panel LED Solution ►Large Screen LED Solution ►Future Products ►Summary Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 2 Target Applications Automotive – 2% Picture Frame – 2% Industrial – 2% Portable DVD – 5% Monitor – 39% LCD-TV – 22% Notebook – 27% Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 3 LED Backlighting Introduction ► LED • backlights dominate the smaller LCD display market Cell phone, GPS, PDA ► Larger display have traditionally used Cold Cathode Fluorescent Lamps (CCFLs) ► LEDs • • now penetrating larger LCD modules Notebooks have largest adoption today Monitor and TVs are emerging market CCFL Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. LED TM 4 LED Backlight Classification ► The LEDs used in backlighting are characterized in two major ways 1. Current capability • • • Standard LED – drive current < 50mA High current LED – drive current 50 – 150 mA High power LED – drive current 150 – 1000mA+ Standard LED Color 2. • • White LEDs Red, Green and Blue LEDs Combined to make white Philips Luxeon K2 High Power LED LED forward voltage depends on color ► • Red ~ 2V, Green ~ 3.5V, Blue/White ~3.5 – 4V Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 5 The LED Advantage ►LEDs • Point source characteristics enable more flexible backlight architectures • • • • • • • • have many advantages compared to CCFL Enables thinner backlight designs Enables advanced backlight architectures Higher efficacy (more light at a give power) – White LEDs only today Longer lifetime (50,000 hrs vs. ~20,000 hrs.) Dimmable – accurate with infinite steps Low voltage drivers reduces complexity Environmentally friendly (CCFLs contain mercury) Rugged – CCFLs are glass and can break easily Reduced IR emission – no interference with remote devices RGB specific advantages Wider color gamut Tunable white point Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 6 LED Driver Challenges – LED Connection Each backlight consists of many LEDs – 3 to 1000+ depending on display size 25V ► LEDs can be connected in series or parallel ► Series Perfect current matching High voltage drivers are more expensive Inefficient for high step up ratio Parallel Needs current matching circuits – less accurate Enables lower voltage drivers Needs many channels = expensive 5V 17V Series/ Parallel Compromise between high voltage and number of drivers Best cost/ performance ratio Most common approach for >8 LEDs = 4S4P Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 7 LED Driver Challenges – Current Driver ► To • • maintain backlight uniformity, all LEDs must be the same brightness For LEDs, light output is dependent on current, not voltage Therefore current needs to be matched • Target for TV = ±1% matching, Target for monitors and notebooks = ±2% Complicated by the fact that LED forward voltages (VF) vary by ±10-15% ► Assume 5V the LEDs have a VF range of 3.0V to 3.6V (Mean = 3.3V) and we want 20mA 5V 5V 5V 5V 5V Vx R Resistor current setting R = (5 – 3.3)/20mA = 85Ω ILED1 = (5 – 3.0)/85 = 24mA ILED2 = (5 – 3.6)/85 = 16mA > Low cost > Poor matching ±20% > Not suitable for backlight Ideal current source = perfect matching Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Real world implementation Active circuit maintains voltage across current setting transistor - Vx VF voltage difference drop across transistor LED current set by Vx/R Matching set by Vx accuracy > Suitable for backlight driver > Freescale has best in class current matching ±1% to ±2% TM 8 LED Driver Challenges – Current Driver ► To • • maintain backlight uniformity, all LEDs must be the same brightness For LEDs, light output is dependent on current, not voltage Therefore current needs to be matched • Target for TV = ±1% matching, Target for monitors and notebooks = ±2% Complicated by the fact that LED forward voltages (VF) vary by ±10-15% ► Assume 5V the LEDs have a VF range of 3.0V to 3.6V (Mean = 3.3V) and we want 20mA 5V 5V 5V 5V 5V Vx R Resistor current setting R = (5 – 3.3)/20mA = 85Ω ILED1 = (5 – 3.0)/85 = 24mA ILED2 = (5 – 3.6)/85 = 16mA > Low cost > Poor matching ±20% > Not suitable for backlight Ideal current source = perfect matching Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Real world implementation Active circuit maintains voltage across current setting transistor - Vx VF voltage difference drop across transistor LED current set by Vx/R Matching set by Vx accuracy > Suitable for backlight driver > Freescale has best in class current matching ±1% to ±2% TM 9 LED Driver Challenges – Current Driver ► To • • maintain backlight uniformity, all LEDs must be the same brightness For LEDs, light output is dependent on current, not voltage Therefore current needs to be matched • Target for TV = ±1% matching, Target for monitors and notebooks = ±2% Complicated by the fact that LED forward voltages (VF) vary by ±10-15% ► Assume 5V the LEDs have a VF range of 3.0V to 3.6V (Mean = 3.3V) and we want 20mA 5V 5V 5V 5V 5V Vx R Resistor current setting R = (5 – 3.3)/20mA = 85Ω ILED1 = (5 – 3.0)/85 = 24mA ILED2 = (5 – 3.6)/85 = 16mA > Low cost > Poor matching ±20% > Not suitable for backlight Ideal current source = perfect matching Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Real world implementation Active circuit maintains voltage across current setting transistor - Vx VF voltage difference drop across transistor LED current set by Vx/R Matching set by Vx accuracy > Suitable for backlight driver > Freescale has best in class current matching ±1% to ±2% TM 10 LED Driver Challenges – Current Driver ► To • • maintain backlight uniformity, all LEDs must be the same brightness For LEDs, light output is dependent on current, not voltage Therefore current needs to be matched • Target for TV = ±1% matching, Target for monitors and notebooks = ±2% Complicated by the fact that LED forward voltages (VF) vary by ±10-15% ► Assume 5V the LEDs have a VF range of 3.0V to 3.6V (Mean = 3.3V) and we want 20mA 5V 5V 5V 5V 5V Vx R Resistor current setting R = (5 – 3.3)/20mA = 85Ω ILED1 = (5 – 3.0)/85 = 24mA ILED2 = (5 – 3.6)/85 = 16mA > Low cost > Poor matching ±20% > Not suitable for backlight Ideal current source = perfect matching Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Real world implementation Active circuit maintains voltage across current setting transistor - Vx VF voltage difference drop across transistor LED current set by Vx/R Matching set by Vx accuracy > Suitable for backlight driver > Freescale has best in class current matching ±1% to ±2% TM 11 LED Driver Challenges – Power Dissipation ► VF • • • • • variation between LEDs increases power dissipation/ heating Typical white LED spec’d with VF = 3.0V min, 3.6V max. VS Binning can be used to sort LEDs and reduce this variation Reducing this to a minimum, helps keep power dissipation down However there is a trade off with current accuracy Freescale products typically around 500mV For a string of 12 LEDs, this means VF(total) = 36V to 43.2V In reality, statistical distribution may give 2V - 3V variation The linear drivers have to absorb this voltage difference (VVAR) In addition, there is a minimum voltage in the drivers needed for the current driver (VMIN) • PDiss = ((n – 1) x ILED x (VMIN + VVAR)) + ILED x VMIN • • e.g. For 8 channels, driving 50mA LEDs with average variation of 3V PDiss = ((8 -1) x 50.10-3 x (0.5 + 3)) + 50.10-3 x 0.5 = 1.08W VVAR + VMIN ► Dynamic Headroom Control (DHC) • To reduce power dissipation, the string voltage (VS) should be kept to a minimum • As LED voltage is unknown, fixed output voltage must assume worst case (43.2V) • DHC measures the voltage connected to the LED driver and adjusts the output voltage (VS) to the minimum capable of driving the LEDs – 500mV for FSL drivers • Delivers minimum possible dissipation/ highest efficiency for LED driver Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 12 LED Drivers – Linear vs. Switching ►Freescale products use linear current ►Alternatively can use switching driver drivers Linear Driver Switching Driver Single DC:DC Linear driver absorbs string difference = higher power dissipation Fewer expensive external components = lower cost = smaller footprint Separate DC:DC per string Switcher absorbs string difference = higher efficiency Requires separate inductor+capacitors/ string = higher cost = large PCB area Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 13 LED Placement ►Edge lit backlight Backlight Driver • • LEDs along edge of display Generally used in smaller panels • • • • • Backlight Driver Backlight Driver 30”+ Enables advanced architectures • backlight LED array behind LCD Used in larger panels <2mm thick for notebook Uniformity worst than direct backlight Backlight Driver Now in TV’s up to 40” Enables super thin backlight ►Direct Scanning and local dimming Good uniformity Especially for larger displays Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 14 Advanced LED Backlight Architectures ►Advanced LED backlight architectures are being used to overcome drawbacks of the LCD technology ►One ►A such drawback is contrast ratio second is power consumption ►Local • • Local Dimming dimming improves both Backlight is divided in to a number of zones The backlight is then adjusted depending on the picture content With Contrast ratio improvements to >500,000:1 possible – Without Standard LCD ~ 5000:1 Reduces power dissipation up to 60% – The backlight consumes 30%+ of power in LCD-TVs Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 15 Advanced LED Backlight Architectures ►Another ►This • • • • • problem with LCD is motion blur can be improved using scanned backlights Backlight is divided into rows Light is scanned down the display at frame rate One or more rows can be illuminated at a time Eye tricked in to seeing faster refresh This removes the blur effect ►Often With Scan combined with local dimming Without Scan Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 16 The Freescale Advantage ►Experience • Assembled expert team with many years LED driver experience • System group engaged with major LED backlight vendors for complete solution approach Convert LCD panels to LED backlight Understand all aspect of backlight design Deep understanding of LED design challenges ►Technology • Freescale SMARTMOS™ technology • Enables integration of high density control logic, with integrated power device and accurate analog control circuits ►Proven Capability • Our existing custom products are the highest performing LED drivers on the market • Standard products offer innovative features and differentiated performance to stand out from the competition Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 17 Notebook and Mid-size Display LED Drivers ► Typically ► Edge-lit ► The • use white, standard LEDs (20 to 30mA) is used in almost all these displays number of standard white LEDs varies depending on the application 10 – 100 LEDs will be used depending on screen size 7” = 10-16 LEDs 12” = ~40 LEDs 14.1” = ~54 LEDs 15.4” = ~60 LEDs • Typical applications have a single driver ► Drivers • • are powered from either Internal 5V or 12V Direct from battery 7 to 20V in notebooks Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 18 MC34845 Introduction ►MC34845 is a 6-channel, fully integrated white LED driver Target panel sizes from 10” to 17” • Can drive max.96 LEDs from a single device (16S6P) • Single chip solution in many applications ►Targeted Notebook Applications Industrial/ Instrumentation Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Picture Frame Portable DVD Medical TM 19 MC34845 Advantages ►Advantages • 60V boost output capability supplies more LEDs in series • Drives 96 LEDs from single device using standard 6-pin interconnect Small BOM to minimize footprint and cost Includes integrated boost FET PWM up to 25kHz to remove audible noise concerns • Advanced dynamic headroom control to reduce power dissipation in IC and improve backlight efficiency • High speed drivers provides for improved PWM range even at 25kHz • Minimum input pulse down to 200ns Linear range from 0.4% to 100% Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 20 MC34845 Notebook LED Driver ►Features Input voltage range 5V to 21V • 2.0A Integrated boost • 600kHz or 1.2MHz Output Voltage up to 60V • 6 channel LED driver • • • • • • • VDC1 VDC2 SLOPE SW Regulators Boost Controller PWM frequency up to 100kHz 30,000:1 dimming range 200ns minimum pulse OVP DHC / Fault Detector OVP VOUT I0 EN I1 PWM 6 channel 30mA current driver WAKE Dynamic Headroom control LED open/short protection User programmable OVP OTP, OCP, UVLO fault detection Shutdown to <1μA 24-Ld QFN 4mm x 4mm x 0.65mm package Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. SW COMP Direct PWM input control • Up to 30mA LED current ±2% current matching VIN OCP/OTP/UVLO I2 I3 I4 I5 ISET DGND GNDA PGND TM 21 Monitor and TV LED Drivers ►For monitors and TVs both white and RGB LEDs are used ►Can use all types of LED from standard to high power (50mA to 350mA) ►Edge-lit is most popular today with direct backlight in high end models only ►The LED • • • number of LEDs depends on the size of panel, and the type of Can use 2000 – 4000 standard LEDs For high power LEDs, a few hundred units are used Requires multiple drivers per system ►Power typically comes from a 24V supply Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 22 MC34844 Introduction ►MC34844 is a 10-channel, fully integrated white LED driver Target panel sizes from 14” to 27” • Can drive max.160 LEDs from a single device (16S10P) • Single chip solution in many applications ►Targeted Monitors Applications TVs Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. 24” white LED monitor driven using single MC34844 Industrial/ Instrumentation Medical TM 23 MC34844 Advantages ►Advantages • 10-channel, 60V drivers support up to 160 LEDs • One chip supports monitors up to 24” Small BOM to minimize footprint and cost Includes integrated boost FET PWM up to 25kHz to remove audible noise concerns PWM synchronizing capability to remove visual noise artifacts Advanced dynamic headroom control to reduce power dissipation in IC and improve backlight efficiency • High speed drivers provides for improved PWM range even at 25kHz • • • • • Minimum pulse down to 200ns Linear range from 0.3% to 100% Supports I2C/SM-Bus/PWM control inputs Temperature/optical sensor inputs Closed loop control for improved uniformity over lifetime/temp Ambient backlight control for improved battery life Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 24 MC34844 White LED Driver ► Features • • • • • • • • • • • COMP Boost Controller SW VOUT PGND Clock/ PLL PGND REG 2 CK VDC2 V sense M/~S PWM PWM Generator SCK I2C/ SM-Bus interface SDA FAIL I0 10 channel 50mA current mirror I1 I2 I3 I4 I5 A0/SEN PWM synchronizing capability REG 1 EN Up to 50mA LED current ±2% current matching 8-bit programmable for each channel 100Hz to 25kHz 8-bit resolution SW VDC1 OVP Internal PWM generator • 150kHz to 1.2MHz Output Voltage up to 60V 10 channel LED driver • VIN Input voltage of 7V to 28V 3.0A Integrated boost 100Hz to 25kHz I7 Current DAC I8 ISET PIN NIN I2C/ SM-Bus interface Dynamic headroom control Temperature/optical compensation loops LED short detection User programmable OVP OTP/OCP/UVLO lockout 32-Ld QFN 5mm x 5mm x 1mm package Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. I6 I9 Temp/Opto loop control GND OCP/OTP/UVLO GND TM 25 Road Map 50” 40” Local dimming direct backlight chipset solution Edge-lit LED Driver Multiple devices Television 60” Notebook Netbook Monitor 30” 20” MC34844 10-channel Driver + DC:DC MC34845 6-channel Driver + DC:DC 10” Next gen. Mon. Adv 8-channel Driver + DC:DC MC34846 6-channel Driver + DC:DC (TBD) 4-channel Driver + DC:DC 2008 Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. 2009 2010 TM 26 MC34846 Introduction ►MC34846 is a 6-channel, advanced functionality white LED driver Target panel sizes from 10” to 17” • Integrates advanced features for audible/visual noise reduction • ►Targeted Notebook Applications Industrial/ Instrumentation Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. Picture Frame Portable DVD Medical TM 27 MC34846 Advantages ►Advantages • 52V boost output capability supplies more LEDs in series • Drives 84 LEDs from single device using standard 6-pin interconnect Small BOM to minimize footprint and cost Includes integrated boost FET High speed PWM output up to 25kHz • Reduced audible noise • Simplified DC:DC design • Improved efficiency • Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 28 MC34846 Advanced White LED Driver ► Features • • Input voltage range 5V to 24V 2.0A Integrated boost FET • • Output Voltage up to 52V 6 channel LED driver • VIN VDC1 Regulators F_BOOST Boost Controller OVP1 100Hz to 25kHz 10-bit resolution = 1000:1 dimming range 100Hz to 75kHz 200ns minimum pulse 30,000:1 dimming range OVP DHC I0 I1 EN PWM MODE P_RST Dynamic Headroom control User programmable OVP LED open/short detection OTP, OCP, UVLO fault detection Shutdown to <1μA 20-Ld QFN 4mm x 4mm x 0.65mm package Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. SW SW Direct PWM control mode • • • • • • Up to 30mA LED current ±1.5% tolerance Internal PWM generator • 5V to 24V 300kHz to 1.5MHz PWM_SET 6 channel 30mA current driver Logic Control I2 I3 I4 I5 ISET PWM Generator OCP/OTP/UVLO GNDA PGND TM 29 LED Backlight Controllers ►For RGB color control, simple 8-bit MCU is sufficient Freescale solution based on 68HC9S08AW60 • Patented color control system architecture • Package : 44/64LQFP UART LCD TV main Processor Interface 60K Flash FPGA Board Interface User Control Interface Color sensor inputs System Monitoring BDM interface VSS Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. VDD VSSa VDDa TM 30 Freescale Color Management Control System Auto calibration is possible in the manufacturing stage ! Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 31 Small Panel Solutions ►White • LEDs dominate small panel backlighting Cell phones, DSC, smart phone, PDA, MID, GPS… ►Historically have used separate LED driver ►Majority applications now moving to integrated solutions ►Freescale supports this market through integrated solutions only PMIC for portable products Integrates LED driver Future IC Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 32 Summary ►Freescale highly focused on LED backlight market ►Leverage system expertise and Freescale advanced technology to provide differentiated, enabling products ►Freescale ►Future products in volume production today road map to cover all types of LED backlight requirements Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 33 Q&A ► Thank you for attending this presentation. We’ll now take a few moments to review the audience questions, and then we’ll begin the question and answer session. Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. TM 34 TM