LP8543 LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight Literature Number: SNVS604C LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight General Description Features The LP8543 is a white LED driver with integrated boost converter. It has 7 adjustable current sinks which can be controlled by SMBus or I2C-compatible serial interface, PWM input and Ambient Light Sensor (ALS). The boost converter has adaptive output voltage control based on the LED driver voltages. This feature minimizes the power consumption by adjusting the voltage to lowest sufficient level in all conditions. Phase Shift PWM dimming offers further power saving especially when there is poor matching in the forward voltages of the LED strings. Boost voltage can also be controlled through the SMBus/I2C. Internal EEPROM stores the data for backlight brightness and ambient light sensor calibration. Brightness can be calibrated during the backlight unit production so that all units produce the same brightness. EEPROM also stores the coefficients for the LED control equations and the default LED current value. LED current has 8-bit adjustment from 0 to 60 mA. The LP8543 has several safety and diagnostic features. Lowinput voltage detection turns the chip off if the system gets stuck and battery fully discharges. Input voltage detection threshold is adjustable for different battery configurations. Thermal regulation reduces backlight brightness above a set temperature. LED fault detection reports open or LED short fault. Boost over-current fault detection protects the chip in case of over-current event. LP8543 is available in the LLP 24-pin package. High-voltage DC/DC boost converter with integrated FET 5.5V to 22V input voltage range to support 2x, 3x and 4x Li-Ion batteries. PWM phase shift control with adaptive boost output to increase efficiency compared to conventional boost converters topologies PWM brightness control for single wire control and standalone use Digital Ambient light sensor interface with userprogrammed ambient light to backlight brightness curve Easy-to-use EEPROM calibration for current, intensity and ambient light response setting Seven LED drivers with LED fault (short/open) detection Eight-bit LED current control Internal thermal protection and backlight safety dimming feature Two wire, SMBus/ I2C-compatible control interface Low-input voltage detection and shutdown Minimum number of external components LLP 24-pin package, 4 x 4 x 0.8 mm Applications Medium sized (>10 inches) LCD Display Backlight LED Lighting Typical Application 30085870 (c) 2011 Texas Instruments Incorporated 300858 www.ti.com LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight November 14, 2011 LP8543 Typical Application, Using 7 Outputs for Display1 30085871 Typical Application, Stand-Alone Mode 30085869 www.ti.com 2 LP8543 Connection Diagrams and Package Mark Information 24-pin Leadless Leadframe Package (LLP) 4.0 x 4.0 x 0.8mm, 0.5 mm pitch NS Package Number SQA24A 30085872 30085875 Bottom View Top View Package Mark 30085896 Package Mark - Top View U = Fab Z = Assembly XY = 2-Digit Date Code TT = Die Traceability L8543SQ = Product Identification Ordering Information Order Number Spec/flow Package Marking Supplied As LP8543SQX HFLF L8543SQ 4500 units, Tape-and-Reel 3 www.ti.com LP8543 Pin Descriptions Pin # Name Type 1 GND_SW G Boost ground Description 2 PWM I PWM dimming input. This pin must be connected to GND if not used. 3 IF_SEL I Serial interface mode selection: IF_SEL= Low for I2C-compatible interface and IF_SEL=High for SMBus interface. 4 EN I Enable input pin 5 ALSI I Ambient light sensor frequency input pin. This pin must be connected to GND if ALS is not used. 6 ALSO O Ambient light sensor enable output 7 FAULT OD 8 VDDIO P Digital IO reference voltage 1.65V to 5.5V. Needed in SMBus/I2C and stand alone mode. 9 GND_S G Signal ground 10 SCLK I Serial clock. This pin must be connected to GND if not used. 11 SDA I/O Serial data. This pin must be connected to GND if not used. 12 OUT1 A Current sink output 13 OUT2 A Current sink output 14 OUT3 A Current sink output 15 GND_L G Ground for current sink outputs 16 OUT4 A Current sink output 17 OUT5 A Current sink output. Can be left floating if not used. 18 OUT6 A Current sink output. Can be left floating if not used. 19 OUT7 A Current sink output. Can be left floating if not used. 20 ADR I Serial interface address selection. See serial interface chapter for details. This pin must be connected to GND if not used. 21 FB A Boost feedback input 22 VLDO A LDO output voltage. 470 nF capacitor should be connected to this pin. 23 VIN P Input power supply 5.5V to 22V 24 SW A Boost switch Fault indication output A: Analog Pin, G: Ground Pin, P: Power Pin, I: Input Pin, I/O: Input/Output Pin, O: Output Pin, OD: Open Drain Pin www.ti.com 4 (Note 1, Note 2) Input Voltage Range VIN 5.5 to 22.0V VDDIO 1.65 to 5V V (OUT1...OUT7, SW, FB) 0 to 40V Junction Temperature (TJ) Range -40C to +125C Ambient Temperature (TA) Range (Note 6) -40C to +85C 2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and specifications. VIN VDDIO, VLDO Voltage on Logic Pins (PWM, ADR EN, IF_SEL, ALSO, ALSI) Voltage on Logic Pins (SCLK, SDA, FAULT) V (OUT1...OUT7 SW, FB) Continuous Power Dissipation (Note 3) Junction Temperature (TJ-MAX) Storage Temperature Range Maximum Lead Temperature (Soldering) ESD Rating Human Body Model: Machine Model: -0.3V to +24.0V -0.3V to +6.0V -0.3V to +6.0V Thermal Properties Junction-to-Ambient Thermal Resistance (JA), SQA Package (Note 7) -0.3V to VDDIO 35 - 50C/W -0.3V to +44.0V Internally Limited 125C -65C to +150C (Note 4) (Note 5) 2 kV OUT7: 150V All other pins : 200V Electrical Characteristics (Note 2, Note 8) Limits in standard typeface are for TA = 25C. Limits in boldface type apply over the full operating ambient temperature range (-40C < TA < +85C). Unless otherwise specified: VIN = 12.0V, VDDIO = 2.8V, CVLDO = 470 nF, L1 = 15 H, CIN = 10 F, COUT = 4.7 F. (Note 9) Symbol IIN Parameter Condition Standby supply current Internal LDO disabled EN=L and PWM=L Normal mode supply current LDO enabled, boost enabled, no current going through LED outputs Min Typ Max Units 1 A 3.5 fOSC Internal Oscillator Frequency Accuracy -4 -7 VLDO Internal LDO Voltage 4.5 ILDO Internal LDO External Loading 5.0 mA 4 7 % 5.5 V 5.0 mA Max Units Boost Converter Electrical Characteristics Symbol Parameter Condition Typ 0.12 38 V VIN 12V, VOUT = 38V VIN = 5.5V, VOUT = 38V 400 180 mA BOOST_FREQ_SEL = 0 BOOST_FREQ_SEL = 1 625 1250 RDS-ON Switch ON resistance VMAX Boost maximum output voltage ILOAD Maximum Continuous Load Current fSW Switching Frequency VOV Over-voltage protection voltage VBOOST = 38V VBOOST < 38V tPULSE Switch pulse minimum width Startup delay tDELAY Min ISW = 0.5A kHz VBOOST + 1.6V VBOOST + 4V V no load 50 ns EN_STANDALONE = 1, PWM input active, EN is set from low to high 2 ms 5 www.ti.com LP8543 Operating Ratings Absolute Maximum Ratings (Note 1, Note LP8543 Symbol tSTARTUP IMAX Parameter Condition Startup time (Note 10) SW pin current limit IMAX_SEL[1:0] = 00 IMAX_SEL[1:0] = 01 IMAX_SEL[1:0] = 10 IMAX_SEL[1:0] = 11 Min Typ Max Units 8 ms 0.9 1.4 2.0 2.5 A LED Driver Electrical Characteristics Symbol Parameter Condition ILEAKAGE Leakage current Outputs OUT1 to OUT7 (Voltage on pins 40V) IMAX Maximum Source Current Outputs OUT1 to OUT7 IOUT Output current accuracy (Note 11) Output current set to 20 mA IMATCH Matching OUT1-7 (Note 11) Output current set to 20 mA IMATCH Matching OUT1-6 (Note 11) PWMRES PWM output resolution Typ -1 Max Units 1 A 60 -3 -4 mA 3 4 % 0.8 1.5 % Output current set to 20 mA 0.5 1.35 % fPWM_OUT 4883 Hz 10 fPWM_OUT = 9766Hz 9 fPWM_OUT = 19531Hz 8 Min LED Switching Frequency PWM_FREQ[2:0] = 000b PSPWM_FREQ[1:0] = 00b, PWM_MODE = 0 -4% -7% Max LED Switching Frequency PWM_FREQ[2:0] = 111b, PSPWM_FREQ[1:0] = 11b, PWM_MODE = 0 -4% -7% fLED VSAT Min bit 229 4% 7% 19531 4% 7% Output current set to 20 mA 200 270 330 Output current set to 60 mA 300 400 540 Hz Saturation voltage (Note 12) mV Ambient Light Sensor Interface Characteristics Symbol fALS tCONV Max Units ALS Frequency Range Parameter Condition Min 0.2 2000 kHz ALS Duty Cycle 40 60 % Conversion Time Typ 500 ms PWM Interface Characteristics Symbol fPWM Parameter PWM Frequency Range tSTBY Turn Off Delay tPULSE PWM Input Pulse Width PWMRES PWM input resolution www.ti.com Condition Min Typ 0.1 PWM input low time for turn off, stand-alone mode, slope disabled 50 200 Units 25 kHz ms ns fPWM_IN < 4.5 kHz 10 fPWM_IN = 20 kHz 8 6 Max bit LP8543 Under-Voltage Protection Symbol VUVLO Parameter Condition UVLO Threshold Voltage Min Typ Max UVLO_THR = 1, falling 2.55 2.70 2.94 UVLO_THR = 1, rising 2.62 2.76 3.00 UVLO_THR = 0, falling 5.11 5.40 5.68 UVLO_THR = 0, rising 5.38 5.70 5.98 Units V Logic Interface Characteristics Symbol Parameter Condition Min Typ Max Units 0.4 V 1.0 A 0.4 V 1.0 A 0.2xVDDIO V Logic Input PWM VIL Input Low Level VIH Input High Level 2.2 II Input Current -1.0 V Logic Input EN VIL Input Low Level VIH Input High Level 1.2 II Input Current -1.0 V Logic Input SCLK, SDA, ADR, ALSI, IF_SEL VIL Input Low Level VIH Input High Level II Input Current V 0.8xVDDIO -1.0 1.0 A Logic Outputs SDA, FAULT VOL Output Low Level IOUT = 3 mA (pull-up current) IL Output Leakage Current VOUT = 2.8V 0.3 -1.0 0.5 V 1.0 A 0.5 V 1.0 A Logic Output ALSO VOL Output Low Level IOUT = 3 mA (pull-up current) VOH Output High Level IOUT = -3 mA (pull-up current) IL Output Leakage Current VOUT = 2.8V V -1.0 I2C Serial Bus Timing Parameters (SDA, SCLK) Symbol 0.3 VLDO - 0.5V VLDO - 0.3V (Note 13) Limit Parameter Min Max 400 Units fSCLK Clock Frequency 1 Hold Time (repeated) START Condition 0.6 s 2 Clock Low Time 1.3 s 3 Clock High Time 600 ns 4 Setup Time for a Repeated START Condition 600 ns 5 Data Hold Time 50 ns 6 Data Setup Time 100 ns 7 Rise Time of SDA and SCL 20+0.1Cb 300 ns 8 Fall Time of SDA and SCL 15+0.1Cb 300 ns 9 Set-up Time for STOP condition 600 ns 10 Bus Free Time between a STOP and a START Condition 1.3 s Cb Capacitive Load for Each Bus Line Load of 1 pF corresponds to 1 ns. 10 7 200 kHz ns www.ti.com LP8543 30085898 SMBus Timing Parameters (SDA, SCLK) Symbol fSCLK (Note 13, Note 14) Limit Parameter Units Min Max 100 Clock Frequency 10 1 Hold Time (repeated) START Condition 4.0 kHz 2 Clock Low Time 4.7 3 Clock High Time 4.0 4 Setup Time for a Repeated START Condition 4.7 s 5 Data Hold Time 300 ns 6 Data Setup Time 250 7 Rise Time of SDA and SCL 1000 ns 8 Fall Time of SDA and SCL 300 ns s s 50 s ns 9 Set-up Time for STOP condition 4.0 s 10 Bus Free Time between a STOP and a START Condition 4.7 s Cb Capacitive Load for Each Bus Line Load of 1 pF corresponds to 1 ns. 10 200 ns Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical Characteristics tables. Note 2: All voltages are with respect to the potential at the GND pins. Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150C (typ.) and disengages at TJ = 130C (typ.). Note 4: For detailed soldering specifications and information, please refer to Texas Instruments AN1187: Leadless Leadframe Package (LLP). Note 5: The Human body model is a 100 pF capacitor discharged through a 1.5 k resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin. MIL-STD-883 3015.7 Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125C), the maximum power dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (JA), as given by the following equation: TA-MAX = TJ-MAX-OP - (JA x PD-MAX). Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm. Note 9: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics. Note 10: Start-up time is measured from the moment boost is activated until the VOUT crosses 90% of its target value. Note 11: Output Current Accuracy is the difference between the actual value of the output current and programmed value of this current. Matching is the maximum difference from the average. For the constant current sinks on the part (OUT1 to OUT7), the following are determined: the maximum output current (MAX), the minimum output current (MIN), and the average output current of all outputs (AVG). Two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN/ AVG). The largest number of the two (worst case) is considered the matching figure. The typical specification provided is the most likely norm of the matching figure for all parts. Note that some manufacturers have different definitions in use. Note 12: Saturation voltage is defined as the voltage when the LED current has dropped 10% from the value measured at 2V. Note 13: Guaranteed by design. VDDIO = 1.65V to 5.5V. Note 14: The switching characteristics of the LP8543 fully meets or exceeds the published System Management Bus (SMBus) Specification Version 2.0. www.ti.com 8 LP8543 Typical Performance Characteristics Unless otherwise specified: VBATT = 12.0V, CVLDO = 470 nF, L1 = 15 H, CIN = 10 F, COUT = 4.7 F LED Drive Efficiency, fLED = 19.5 kHz, PSPWM enabled Boost Converter Efficiency 30085825 30085819 Boost Maximum Output Current at VBOOST = 38V Battery Current 30085828 30085827 Boost Converter Typical Waveforms VBOOST = 38V, IOUT = 50 mA Boost Line Transient Response 30085830 30085829 9 www.ti.com LP8543 Typical Waveforms in PSPWM Mode, fLED = 4.2 kHz Typical Waveforms in Normal PWM Mode, fLED = 4.2 kHz 30085831 www.ti.com 30085832 10 3. The LP8543 is a high-voltage LED driver for medium-sized LCD backlight applications. It includes 38V boost converter, 7 current sink outputs for the backlight and an interface for digital Ambient Light Sensor (ALS). LP8543 can be controlled through SMBus or I2C serial interface or PWM input. Light-tofrequency type ambient light sensor can be directly connected to LP8543 and the sensor response vs. LED brightness curve can be programmed in the on-chip EEPROM memory. LP8543 differs from conventional LED drivers due to following advanced features. 1. PHASE SHIFT PWM FEATURE LP8543 supports a state-of-the-art feature called Phase Shift PWM (PSPWM). Key advantages of the PSPWM is improved power efficiency when there is variation in the forward voltages amongst the LED strings. Due to an unmatched LED VF there is a random difference in each string forward voltage. PSPWM optimizes the boost converter output voltage by turning off LED outputs periodically. The lower the brightness, the more strings can be simultaneously off. When the strings with higher forward voltages are turned off, the boost voltage is automatically lowered thereby improving efficiency. The second benefit of PSPWM control is that it will make the boost and battery loading more constant. In other words, the peak current needed from the battery is greatly reduced beause not all LED outputs are simultaneously on. 2. PROGRAMMABLE OUTPUT STRINGS Programmability helps display manufacturers to fit LP8543 to several sizes of displays. The number of output strings in use is a parameter in EEPROM and can be fixed during the manufacturing process of displays. Based on the configuration the device will automatically adjust the phase Shift PWM function for a given number of output strings. LP8543 supports of minimum of 4 strings and a maximum of 7 strings. In this datasheet , strings 1 through 6 are classified as Display1, and string 7 is classified as Display2. 4. 5. 6. 11 INDIVIDUALLY CONTROLLED LED STRING FOR BACKSIDE DISPLAY BACKLIGHT OUT7 string can be either used for main backlight or for possible back side sub display. Separate control allows dimming through I2C interface and reduces extra components or ICs in display module. LED FAULT DETECTION LED fault detection enables higher yield in display manufacturing process and also makes possible to monitor backlight faults during normal operation. Fault test detects both open circuit (string with unconnected or open circuit LED) and short circuit of 2 or more shorted LEDs. Single LED short can also be detected if the amount of LEDs per string and/or the VF variation are sufficiently low. Threshold levels are EEPROM programmable. Fault information is available in the status register and in the open drain active low FAULT output. LED PWM TEMPERATURE REGULATION This feature will decrease the effect of high temperature LED lifetime reduction. LP8543 reduces output PWM of the LEDs at high temperatures and prevents overheating of the device and LEDs. Temperature threshold can be programmed to EEPROM. AMBIENT LIGHT SENSOR INTERFACE WITH USER PROGRAMMABLE CONTROL CURVE Ambient light sensing reduces power consumption and it allows natural backlight in any ambient light condition. Programmability allows display manufacturer and even end user to control sensor to backlight control loop. By integrating this feature LP8543 reduces external component count, wiring and complexity of the design. LP8543 supports digital light-to-frequency type sensors. Prescaler and compensation curve can be programmed in to the EEPROM. www.ti.com LP8543 Functional Overview LP8543 Brightness Control Methods 1. 2. 3. CURRENT CONTROL The 8-bit LED current default value is read from EEPROM when the chip is activated. Current value can be used for fine tuning the backlight brightness between panels. This current setting can be overridden by a register write from the serial interface. Current control range is from 0 to 60 mA with 0.23 mA step. This fine grained current control gives backlight manufacturer possibility to adapt different LED bins in one product and maintain the full PWM control range. There are separate controls for both Display1 and Display2. INTERNAL PWM CONTROL The basic brightness control is register based 8-bit PWM control. There is a piecewise linear transfer curve from register value to LED PWM value and the curve coefficients are stored in the EEPROM. This makes possible to calibrate the 100% brightness and the dimming behavior. LED PWM frequency is selectable from 229 Hz to 19.5 kHz. In addition PSPWM can be used. EXTERNAL PWM CONTROL An external PWM signal can be used to set the brightness of the display. LP8543 measures the duty www.ti.com 4. 12 cycle of this input signal to calculate the output PWM value. Input PWM frequency can vary from 100 Hz to 25 kHz. Based on the configuration selected, this external PWM control can linearly reduce the brightness from the value set by the Brightness Register. This external PWM control can also be used as the only control for LP8543. In this case, when PWM input is permanently low, the chip is turned off. When there is signal in PWM input, the chip turns on and adjusts brightness according to PWM signal duty cycle. In addition, PSPWM can also be used in this mode. AMBIENT LIGHT SENSING External ambient light sensor can be used for controlling the brightness of the LEDs. Light-to- Frequency type light sensor can be connected to ALSI input in LP8543 for ambient light compensation. Transfer curve coefficients for response setting are stored in EEPROM. LP8543 has an enable output, ALSO to activate the light sensor (active high/low, programmed to EEPROM). Light sensor supply voltage can be taken from the 5V regulator in LP8543. Ambient light control is possible for Display1 (4-7 outputs). Energy Efficiency LP8543 has an internal EEPROM to store different control parameters which allows calibrating the backlight brightness at various brightness settings so that every display has exactly the same brightness and several LP8543 circuits can be used in the same display if needed. Programming the EEPROM is easy. User needs to write the data in the shadow RAM memory and give the EEPROM write command. On-chip boost converter produces the needed erase and program voltages, no external voltages other than normal input voltage are required. Calibration in backlight or display production can be done according to the flowchart below The voltage across the LED drivers is constantly monitored and boost voltage is adjusted to minimum sufficient voltage when adaptive boost mode is selected. Inductive boost converter maintains good efficiency over wide input and output operating voltage ranges. The boost output has over voltage protection limiting the maximum output to 38V. The boost is internally compensated and the output voltage can be either controlled with 5-bit register value or automatically adjusted based on the LED driver voltages. LP8543 has an internal 5V LDO with low current consumption. The 5V LDO can supply 5 mA current for external devices like ALS (Ambient Light Sensor). LDO is switched off in standby mode. The internal LDO is used for powering internal blocks as well; therefore the 470 nF CVLDO capacitor must be used even if external load is not used. Serial Communication LP8543 supports two serial protocols: SMBus and I2C. IF_SEL input is used to determine the selection. SMBus interface is selected when IF_SEL is high and I2C is selected when IF_SEL is low. 30085803 13 www.ti.com LP8543 Calibration LP8543 Block Diagram 30085874 www.ti.com 14 LP8543 LED Driver Control BASIC OPERATION Principle of the LED driver control is shown in the following figure: 30085804 Principle of the LED Control Methods LED CURRENT CONTROL LP8543 is designed to be flexible to support backlighting Two 8-bit EEPROM registers, Display1 current and Disneeds for the main display as well as lighting needs of a sub play2 current (addresses B0H and B1H) hold the default display (also for e.g. keyboard lighting or status LED) when LED string current for the Display1 and Display2 groups rerequired. In addition, a variety of PWM options are supported spectively. The default values are read from EEPROM when to drive the backlight LED strings. Various configurations that the chip is activated. When required the LED current can be are supported using a set of programmable internal registers adjusted also in the registers Display1 and Display2 curand EEPROM are described below. Both the register map rent (addresses 05H and 06H). Use of this register is enabled and the EEPROM memory map are listed at the end of this by setting bit 1 in Config2 register. Default value for <CURdatasheet. RENT SEL> bit is 0, which means that current values in OUTPUT GROUPING EEPROM are used. Current control range is linear from 0 to 60 A with 0.23 mA step. Factory default current for Display1 LP8543 features a total of 7 strings (OUT1-OUT7), which can and Display2 is 20 mA. be arranged into 2 groups (Display1 and Display2). Display1 refers to backlighting for main display and Display2 refers to LED ON/OFF CONTROL lighting for a sub display. Number of outputs used for Display1 LED strings can be activated with 100% PWM by writing can be defined using EEPROM register bits, as shown in the <DRV[7:0]> bits high. All these controls are in Direct contable below. LP8543 supports a minimum of 4 strings and a trol register. maximum of 7 strings for Display1. Outputs must be used in order starting from OUT1. Unused outputs can be left open. PWM CONTROL SELECTION When needed OUT7 can be configured for Display2 and it has PWM control of the LED strings can be established through its own current and PWM control registers for independent 4 combinations of user configurable options as shown in the control. EEPROM default factory setting is 6 outputs for Distable below. <PM_MD> and <PWM_SEL> bits are part of play1 and OUT7 for Display2. Config1 Register. TABLE 1. Output Configurations Default setting is external PWM input signal. Each of the option is explained in the following sections. OUTPUT_CONF[1:0] Outputs for Outputs for Display1 Display2 00 OUT1-OUT4 OUT7 01 OUT1-OUT5 OUT7 10 OUT1-OUT6 OUT7 11 OUT1-OUT7 15 www.ti.com LP8543 TABLE 2. PWM Control Selection PWM_MD PWM_SEL 1 1 PWM input (Direct control) 0 1 PWM input pin (Duty cycle based), default 1 0 Brightness register 0 PWM input pin (Duty cycle based) and Brightness register 0 PWM source In addition Ambient light sensor (when used) and on-chip temperature regulation also influence the output PWM control. This is described later. A. Direct PWM Input Control Display1 group can be directly controlled with external PWM signal (bypassing all the PWM logic) by setting <PWM_MD> and <PWM_SEL> bits high. Outputs will be active when the PWM input pin is high, and when the input is low the outputs will be off. Input PWM frequency can vary from 100 Hz to 25 kHz. Display2 is not controlled with this signal. Note: In this mode, Ambient Light sensor and PSPWM scheme do not influence the output PWM. B. PWM Input Pin Control (Duty Cycle-based) An external PWM signal can be used to set the brightness of the Display1 group. LP8543 measures the duty cycle of this input signal to calculate the output PWM value. Input PWM frequency can vary from 100 Hz to 25 kHz. Output PWM frequency is set by EEPROM registers. Note: In this mode, Ambient Light compensation and PSPWM scheme can be also used. C. PWM Control Using Brightness Register Generation of PWM for LED strings can be based on Brightness register value. For Display1 group, this scheme is enabled when <PWM_SEL> bit is set to 0 and <PWM_MD> is set to 1. Display2 group has the brightness register control enabled by default. Two separate 8-bit registers Displ1 brightness and Displ2 brightness store the brightness values for Display1 and Display2 respectively. For Display1, this 8-bit brightness value from the register is converted to 10-bit LED PWM value using a three-part piecewise linear transfer curve as shown below. This makes it possible to calibrate the 100% brightness and the dimming behavior. The curve coefficients are stored in the EEPROM and are user programmable if needed. The LED PWM frequency is set by EEPROM register. Note: In this mode, Ambient Light compensation and PSPWM scheme can be also used. www.ti.com 30085821 Three-Segment Transfer Curve Example D. PWM Pin and Register Control In this mode, PWM control pin can linearly reduce the brightness of Display1 from the value set by the Brightness Register and Ambient Light sensor. Same controls can be used as in brightness register based PWM control. Output PWM frequency is set by EEPROM registers. This mode is compatible with Intel DPST (Display Power Saving Technology). STAND ALONE MODE LP8543 can be set to operate in stand alone mode, where LP8543 operates without I2C / SMBus and EN and PWM input pins are the only controls for the device. To enable standalone mode, EEPROM bit <EN_STANDALONE> must be set to 1 in register B4h. In this mode PWM pin sets the brightness and with EN pin the backlight can be turned on. When PWM or EN input pin is permanently low, the chip is turned off. Turn off time is typically 50 ms. When there is signal in PWM input and EN is high, the chip turns on and adjusts brightness according to PWM signal duty cycle. All settings needed for operation like LED current, number of LEDs etc. are obtained from EEPROM. If only one signal control is needed, the EN and PWM pin can be tied together and PWM signal can be connected to this. Stand alone mode is useful in applications where I2C or SMBus control is not possible or available to use. AMBIENT LIGHT COMPENSATION LP8543 supports an external ambient light sensor to control the backlight brightness (Display1) and its usage is controlled with two bits in the Config2 register, namely <ALSO_EN> and <ALSO_CALC_EN>. <ALSO_EN> bit controls enabling/ disabling of the sensor itself, and <ALSO_CALC_EN> bit determines whether the ALS measurement data will be used by an external processor (Host) or by LP8543's internal control logic to control the brightness. If <ALSO_EN> bit is 1 the ALSO output pin is set high and the input frequency measuring is enabled. Frequency is measured for 500 ms, and the result is divided with 10-bit prescaler (defined in EEPROM), resulting in a 10-bit value. This 10-bit result can be read from ALS MSB and ALS LSB registers. ALS MSB register must be read first followed by ALS LSB register. If ALS_CALC_EN bit is set to 0, then the measurement data is not used by LP8543's internal PWM logic but left for the host to adjust the brightness. On the other hand if the ALS_CALC_EN bit is set to 1, ALS measurement result will control backlight brightness in all but direct external PWM control mode. The measured ALS value 16 Phase shift frequency can either be the same as the PWM frequency or a lower frequency can be selected with <PHASE_SHIFT_FREQ[1:0]> EEPROM bits. At highest 19.5 kHz PSPWM frequency, the boost will use a constant voltage based on the highest VF string because of timing constraints of the high PWM frequency. PSPWM is enabled by default, but it can be disabled by setting <DISABLE_PS> EEPROM bit to 1. Two PSPWM modes are available. PSPWM mode is selected with <PWM_MODE> EEPROM bit. Difference between modes is in the PWM frequencies available. PWM and PSPWM frequency settings are shown in Table 4. Number of strings simultaneously on in PSPWM mode with different PWM values and different output configurations is shown in the following diagram. TABLE 3. Slope Selections SLOPE_SEL[1:0] Slope 00 130 ms 01 0.5s 10 1.0s 11 2s ALSO output can be used as GPO if not used for ALS control. ALSO pin state is then controlled with <ALSO_EN> register bit. PHASE SHIFT PWM (PSPWM) PSPWM improves the system efficiency by optimizing the boost converter voltage on a cycle by cycle basis instead of maintaining a constant voltage based on the highest VF string. PSPWM scheme can be used for Display1 group. Phase shift PWM control principle is illustrated in the picture below using an example of 6 string implementation and 41.7% brightness setting. In a 6-string implementation, each of the string supports a maximum of 16.67% (1/6) of the total backlight brightness. The brightness set value in this example is 41.7%. Hence two strings are fully on (2 x 16.67% = 33.33%) and one string is 50% on (0.5 x 16.67% = 8.34%). This pattern of two 100% and one 50% strings is then cycled through all 6 output strings. After 6 cycles the brightness value is changed to 83.33%, resulting in 5 LEDs fully on (5 x 16.67%). 30085806 Number of Simultaneously Active Strings 30085805 Principle of the PSPWM Operation 17 www.ti.com LP8543 is converted to PWM value using a three segment linear curve. The calculated PWM value is used as a multiplier for the LED PWM value obtained from brightness register, PWM input pin or combination of both depending which mode is selected. The conversion curve parameters are stored in EEPROM memory. Conversion curve is similar as in PWM control. Smoothing filter is used to prevent rapid changes. Smoothing filter has EEPROM programmable slopes from 0 to 2s. The slope defines the time it takes to change brightness from one value to next. Slope control can be also used to smooth changes to backlight brightness caused by other PWM controls (brightness register or external PWM input). LP8543 TABLE 4. PSPWM Frequency Selection in EEPROM Registers (N = number of strings used) PWM_MODE = 0 PWM_MODE = 1 PWM_FREQ[2:0] + PSPWM_FREQ[1:0] PWM Frequency (Hz) Shift Frequency (Hz) 00000 992 992 992/N 229 229 x N 00001 992 496 496/N 305 305 x N 00010 992 248 248/N 381 381 x N 00011 992 124 124/N 458 458 x N 00100 1526 1526 1526/N 534 534 x N 00101 1526 763 763/N 610 610 x N 00110 1526 382 382/N 687 687 x N 00111 1526 191 191/N 763 763 x N 01000 1983 1983 1983/N 839 839 x N 01001 1983 993 993/N 916 916 x N 01010 1983 496 496/N 992 992 x N 01011 1983 248 248/N 1068 1068 x N 01100 2441 2441 2441/N 1144 1144 x N 01101 2441 1221 1221/N 1221 1221 x N 01110 2441 610 610/N 1297 1297 x N 01111 2441 305 305/N 1373 1373 x N 10000 2974 2974 2974/N 1450 1450 x N 10001 2974 1487 1487/N 1526 1526 x N 10010 2974 744 744/N 1602 1602 x N 10011 2974 372 372/N 1678 1678 x N 10100 3965 3965 3965/N 1755 1755 x N 10101 3965 1983 1983/N 1831 1831 x N 10110 3965 991 991/N 1908 1908 x N 10111 3965 496 496/N 1983 1983 x N 11000 4883 4883 4883/N 2060 2060 x N 11001 4883 2441 2441/N 2671 2671 x N 11010 4883 1221 1221/N 3203 3203 x N 11011 4883 610 610/N 3737 3737 x N 11100 19531 19531 19531/N 4270 4270 x N 11101 19531 9766 9766/N 4808 4808 x N 11110 19531 4883 4883/N 9766 9766 x N 11111 19531 2441 2441/N 19531 19531 x N www.ti.com 18 Output Frequency Output Frequency (Hz) (Hz) Shift Frequency (Hz) LP8543 TABLE 5. PWM Frequencies with Phase Shift Disabled PWM_MODE = 0 PWM_MODE = 1 PWM_FREQ[2:0] + PSPWM_FREQ[1:0] PWM Frequency (Hz) Output Frequency (Hz) 00000 992 229 00001 992 305 00010 992 381 00011 992 458 00100 1526 534 00101 1526 610 00110 1526 687 00111 1526 763 01000 1983 839 01001 1983 916 01010 1983 992 01011 1983 1068 01100 2441 1144 01101 2441 1221 01110 2441 1297 01111 2441 1373 10000 2974 1450 10001 2974 1526 10010 2974 1602 10011 2974 1678 10100 3965 1755 10101 3965 1831 10110 3965 1908 10111 3965 1983 11000 4883 2060 11001 4883 2671 11010 4883 3203 11011 4883 3737 11100 19531 4270 11101 19531 4808 11110 19531 9766 11111 19531 19531 19 www.ti.com LP8543 Device Thermal Regulation LP8543 has an internal temperature sensor which can be used to measure the junction temperature of the device and protect the device from overheating. During thermal regulation, LED PWM is reduced by 4% of full scale per C whenever the temperature threshold is reached. I.e., with 100% PWM value the PWM goes to 0% 25C above threshold temperature. With lower PWM start value 0% is reached earlier. Temperature regulation is enabled automatically when the chip is enabled. 11-bit temperature value can be read from Temp MSB and Temp LSB registers, MSB should be read first. Temperature limit can be programmed in EEPROM as shown in the following table. TABLE 6. Over Temperature Limit Settings TEMP_LIM[1:0] Over Temperature Limit (C) 00 100 01 110 10 120 11 130 www.ti.com 30085823 Internal Temperature Sensor Readings 20 EEPROM memory stores various parameters for chip control. The 256 bit EEPROM memory is organized as 32 x 8 bits. The EEPROM structure consists of a SRAM front end and the Non-volatile memory (NVM). SRAM data can be read and written through the serial interface. To erase and write NVM, separate commands need to be sent. Erase and Write voltages are generated on-chip, no other voltages than normal input voltage are required. A complete EEPROM memory map is shown in the chapter LP8543 EEPROM Memory Map. EEPROM structure is described in the figure below. User has read and write access to SRAM part of the EEPROM directly through I2C / SMBus when PWM calculation is not enabled; i.e., <BL_CTL> = 0 and external PWM pin = low. To see whether the EEPROM can be accessed user can read <EE_READY> bit. ALS and brightness coefficient curves (address A0h - Afh) and empty EEPROM cells (address B4h - 30085839 EEPROM Memory Control and Usage Principle 21 www.ti.com LP8543 BBh) have only NVM and SRAM. Other EEPROM cells have also EEPROM registers. For the cells which have also EEPROM registers, the changes made to SRAM does not take effect until update command is sent. This is done by setting EE_UPDATE and EE_READ bits to 1. After an update, these bits must be set back to 0. For EEPROM bits which do not have registers, changes take effect immediately. At startup the values in NVM part of the EEPROM is loaded to SRAM and to EEPROM registers. User can also load values from NVM to SRAM and EEPROM registers by writing EE_READ to 1. To write SRAM values to NVM user needs to first erase EEPROM and the program it. This is done by first writing EE_ERASE to 1 and then 0. At this point NVM is erased. To burn new values to NVM, user needs to write EE_PROG to 1 and then 0. The LP8543 generates the needed erase and write voltage from boost output voltage. EEPROM LP8543 automatically based on LED driver saturation. In adaptive mode the boost output voltage control steps are 0.25V. Enabling the adaptive mode is done with <BOOST_AUTO> bit in Boost Control register. If boost is started with adaptive mode enabled (default) then the initial voltage value is defined with EEPROM bits at address 29H in order to eliminate long iteration time when the chip is started. If adaptive mode is enabled after boost startup, then the boost will use register 07H values as initial voltage value. The output voltage control changes the resistor divider in the feedback loop. The following figure shows the boost topology with the protection circuitry. Boost Converter OPERATION The LP8543 boost DC/DC converter generates a 10...38V supply voltage for the LEDs from 5.5...22V input voltage. The output voltage is controlled with a 5-bit register in 1V steps. The converter is a magnetic switching PWM mode DC/DC converter with a current limit. The topology of the magnetic boost converter is called CPM (current programmed mode) control, where the inductor current is measured and controlled with the feedback. Switching frequency is selectable between 625 kHz and 1.25 MHz with EEPROM bit <BOOST_FREQ>. Boost is enabled with <EN_BOOST> bit. User can program the output voltage of the boost converter or use adaptive mode where boost output voltage is adjusted 30085840 PROTECTION Four different protection schemes are implemented: 1. Over-voltage protection limit changes dynamically based on output voltage setting -- Over-voltage protection limit changes dynamically based on output voltage setting. -- Keeps the output below breakdown voltage. -- Prevents boost operation if battery voltage is much higher than desired output. 2. SW current limiting, limits the maximum inductor current. 3. Over-current protection enables fault flag and shuts down boost converter in over-current condition. 4. Duty cycle limiting. TABLE 7. Boost Output Voltage Controls VPROG[4:0] Bin Dec Volts 00000 0 10 00001 1 11 00010 2 12 00011 3 13 00100 4 14 ... ... ... 11011 27 37 11100 28 38 ADAPTIVE BOOST CONTROL Adaptive boost control function adjusts the boost voltage to the minimum sufficient voltage for proper LED driver operation. When PSPWM is used the output voltage can be adjusted for every phase shift step separately except in 19.5 kHz PSPWM mode due to timing constraints. To enable PSPWM to each phase, the <BOOST_MODE> EEPROM bit must be 0. This enables power saving when strings have mismatch in VF voltages. The correct voltage for each string is stored and used in predicting when the boost has to start increasing voltage for the next step. The boost setup time can be defined with two EEPROM bits. Principle of the boost voltage adjustment with PSPWM is illustrated below. If higher PWM value is used then more strings are on at the same time, and voltage is adjusted based on highest VF on simultaneously active strings. MANUAL OUTPUT VOLTAGE CONTROL User can control the boost output voltage with Boost_output (07H) register when adaptive mode is disabled; i.e., <BOOST_AUTO> = 0. www.ti.com Voltage (typical) 22 LP8543 30085842 Normal Operation, High PWM Value If one LED driver voltage is below Low, boost voltage will be increased. This is seen in the following figure. 30085841 Boost Adaptive Voltage Control for 5-String PSPWM When adaptive boost mode is selected the voltages across the LED drivers are constantly monitored. There are three voltage thresholds used, Low, Mid and High. Low and High thresholds are adjustable with 3 EEPROM bits. Low threshold range is from 0.5V to 2.25V and High threshold range is from 3 to 10V. Mid threshold is set 0.5V above Low threshold. Threshold levels are listed in the table below. Adjustability is provided to enable adaptation to different conditions. If there is a lot of variation between LED string VF, then higher threshold levels must be used to avoid false fault indications. If there is low variation between LED string VF, then lower thresholds are recommended to maintain good efficiency. Fault detection chapter describes how these thresholds are used also for fault detection. 30085843 Boost voltage too Low TABLE 8. LED Voltage Comparator Thresholds EEPROM bits If all driver voltages are above Mid threshold (or any of the voltages in PSPWM adaptation mode and with low PWM value), boost voltage will be lowered. Decision is always based on number of strings active at the same time. In the illustrations 6 outputs are active, which basically means close to 100% PWM value with PSPWM. Threshold (V) LED_FAULT_THR[5:3] (HIGH comparator) DRV_HEADR_CTRL[2:0] (LOW comparator) Low High 000 0.50 3 001 0.75 4 010 1.00 5 011 1.25 6 100 1.50 7 101 1.75 8 110 2.00 9 111 2.25 10 Mid Low + 0.5V If only one string is on at a time (Brightness value lower than 100% divided by number of strings) the voltage for each string is adjusted so that the voltage across the driver will fall between Low and Mid threshold. If more strings are on at the same time (high PWM value, or PSPWM not used) the situation looks like in the following diagram. In this diagram 6 outputs are on at the same time. In normal operation voltages across all LED driver outputs are between high and low threshold. 30085844 Boost voltage too High 23 www.ti.com LP8543 Fault Detection LP8543 has fault detection for LED fault, low-battery voltage, overcurrent and thermal shutdown. The open drain output pin (FAULT) can be used to indicate occurred fault. The cause for the fault can be read from status register. Refreshing the <BL_CTL> bit high will reset the fault register and fault pin state. LED FAULT DETECTION There are two methods of detecting the LED fault. First method is based on measuring the voltage on LED driver pins (analog fault detection) and another is based on adaptive boost voltage hopping between strings (digital fault detection). The used fault detection mode is selected in EEPROM as well as the threshold levels. <FAULT_SEL[1:0]> bits selects the used mode as follows: 30085845 Open Fault TABLE 9. LED Fault Mode Selection FAULT_SEL[1:0] If one or more LEDs are shorted, this causes the voltage to rise in this LED driver output pin above the high threshold. This causes short fault detection as seen in the following figure: Fault mode 00 No fault detection 01 Analog fault detection based on LED driver voltage 10 Digital fault detection based on boost voltage hopping 11 Both analog and digital fault detection Two fault detection methods are used to detect faults in different conditions. Analog detection works better with high PWM values (in PSPWM mode) where many strings are active at a same time. It does not work when only one string is active at a time, because it is based on comparing driver voltages on strings active simultaneously. Digital fault detection is used to complement this case. Digital fault detection works better with low PWM values, where not all strings are on at the same time. Digital short detection works only with cases where one string is active at the same time. 30085846 Short Fault DIGITAL FAULT DETECTION With digital fault detection the voltage hopping between LED strings is monitored in PSPWM mode. In normal PWM mode or with high PWM values with PSPWM mode this does not apply. If there's open in one of the LED strings, the LED driver output pin will drop to 0V. When this happens the boost will try to increase the voltage to get enough headroom for the driver. When the voltage for one string reaches maximum voltage (38V) and the difference between consecutive LED strings is higher than set threshold level an open LED fault is detected. If all voltages are close to 38V then the threshold condition is not met and no fault is detected. If the LED output is shorted to GND it will be detected same way. Open fault detection is seen in the following figure: ANALOG FAULT DETECTION When analog fault detection mode is selected, the voltages across the LED drivers are constantly monitored. The same threshold levels (Low, Mid and High) are used for fault detection to adjust the boost voltage. If one of the LED strings has an open fault (LED driver output pin has no contact to LED string), the output pin voltage drops to 0V. When this happens the boost voltage will be adjusted higher to get enough headroom, but at some point the voltage for all other strings will rise over the high threshold. In this case the LP8543 detects open fault, and adjusts the boost voltage based on other LED strings needs, i.e., the faulty LED string voltage is not used anymore for adjusting boost output voltage. If the LED driver output pin is shorted to GND the fault detection works exactly the same. This situation with 6 LEDs active at the same time is illustrated in the following diagram: www.ti.com 24 30085847 UNDER-VOLTAGE DETECTION LP8543 has detection for too low VIN voltage. Threshold level for the voltage is set with EEPROM register bits as seen in the following table: Digital Open Fault Detection If there is one or more LEDs shorted in one string, the boost will drop the voltage for this string. When the difference between consecutive LED strings is higher than set threshold level a short LED fault is detected. This is described in the following figure: TABLE 11. Under-Voltage Detection Thresholds 30085848 Threshold level is programmed to EEPROM as shown in the following table. Threshold level adjustability is provided to allow adaptation to different LED VF used in the application. TABLE 10. Digital LED Fault Detection Thresholds Threshold Voltage (V) 00 3 01 5 10 7 11 9 Threshold (V) 0 6 1 3 Under voltage detection is always on. When under voltage is detected the LED outputs and boost will shutdown, Fault pin will be pulled down (open drain output) and corresponding fault bit is set in status register. Fault can be reset by reading the status register. LEDs and boost will start again when the voltage has increased above the threshold level. Hysteresis is implemented to threshold level to avoid continuous triggering of fault when threshold is reached. Note: Due to the nature of fault detection it is possible to generate false faults during startup etc. conditions. Therefore when fault is detected it is recommended to read the fault/ status register twice to make sure that the first fault is real. If the second reading gives the same result then the fault is real. Digital Short Fault Detection DIG_COMP[1:0] UVLO_THR OVER-CURRENT DETECTION LP8543 has detection for too high loading on the boost converter. When over current fault is detected the LP8543 will shut down and set the fault flag. THERMAL SHUTDOWN If the LP8543 reaches thermal shutdown temperature (150C) the LED outputs and boost will shut down to protect it from damage. Also the fault pin will be pulled down to indicate the fault state. Device will activate again when temperature drops below 130C. When Fault is detected the FAULT pin will be pulled down (open drain output), and corresponding status register bit is set. To clear the fault user must read the status register. Note: LED fault output signal is generated only once for certain fault type. If, for example, open fault occurs, new open 25 www.ti.com LP8543 fault does not cause the FAULT pin to be pulled down uless chip is reset by setting EN pin low and high again. The faults will be seen in the register however. If LED fault is detected, the string which created the fault is no longer used for adjusting the boost voltage. Otherwise the LP8543 operates as normally. Note: Due to the nature of fault detection it is possible to generate false faults during startup etc. conditions. Therefore when fault is detected it is recommended to read the fault/ status register twice to make sure that the first fault is real. If the second reading gives the same result then the fault is real. LP8543 SMBus/I2C Compatible Serial Bus Interface INTERFACE BUS OVERVIEW The SMBus/I2C-compatible synchronous serial interface provides access to the programmable functions and registers on the device. This protocol uses a two-wire interface for bidirectional communications between the IC's connected to the bus. The two interface lines are the Serial Data Line (SDA), and the Serial Clock Line (SCL / SCLK). These lines should be connected to a positive supply, via a pull-up resistor and remain HIGH even when the bus is idle. Every device on the bus is assigned a unique address and acts as either a Master or a Slave depending on whether it generates or receives the serial clock (SCLK). LP8543 is always a slave device. DATA TRANSACTIONS One data bit is transferred during each clock pulse. Data is sampled during the high state of the serial clock (SCL). Consequently, throughout the clock's high period, the data should remain stable. Any changes on the SDA line during the high state of the SCLK and in the middle of a transaction, aborts the current transaction. New data should be sent during the low SCLK state. This protocol permits a single data line to transfer both command/control information and data using the synchronous serial clock. 30085820 Start and Stop The Master device on the bus always generates the Start and Stop Conditions (control codes). After a Start Condition is generated, the bus is considered busy and it retains this status until a certain time after a Stop Condition is generated. A high-to-low transition of the data line (SDA) while the clock (SCLK) is high indicates a Start Condition. A low-to-high transition of the SDA line while the SCLK is high indicates a Stop Condition. 30085849 Bit Transfer 30085850 Each data transaction is composed of a Start Condition, a number of byte transfers (set by the software) and a Stop Condition to terminate the transaction. Every byte written to the SDA bus must be 8 bits long and is transferred with the most significant bit first. After each byte, an Acknowledge signal must follow. The following sections provide further details of this process. Start and Stop Conditions In addition to the first Start Condition, a repeated Start Condition can be generated in the middle of a transaction. This allows another device to be accessed, or a register read cycle. ACKNOWLEDGE CYCLE The Acknowledge Cycle consists of two signals: the acknowledge clock pulse the master sends with each byte transferred, and the acknowledge signal sent by the receiving device. The master generates the acknowledge clock pulse on the ninth clock pulse of the byte transfer. The transmitter releases the SDA line (permits it to go high) to allow the receiver to send the acknowledge signal. The receiver must pull down the SDA line during the acknowledge clock pulse and ensure that SDA remains low during the high period of the clock pulse, thus signaling the correct reception of the last data byte and its readiness to receive the next byte. "ACKNOWLEDGE AFTER EVERY BYTE" RULE The master generates an acknowledge clock pulse after each byte transfer. The receiver sends an acknowledge signal after every byte received. www.ti.com 26 Control Register Read Cycle * Master device generates a start condition. * Master device sends slave address (7 bits) and the data direction bit (r/w = 0). * Slave device sends acknowledge signal if the slave address is correct. * Master sends control register address (8 bits). * Slave sends acknowledge signal. * Master device generates repeated start condition. * Master sends the slave address (7 bits) and the data direction bit (r/w = 1). * Slave sends acknowledge signal if the slave address is correct. * Slave sends data byte from addressed register. * If the master device sends acknowledge signal, the control register address will be incremented by one. Slave device sends data byte from addressed register. * Read cycle ends when the master does not generate acknowledge signal after data byte and generates stop condition. ADDRESSING TRANSFER FORMATS Each device on the bus has a unique slave address. The LP8543 operates as a slave device with the 7-bit address combined with data direction bit. Slave address is pin-selectable as follows: TABLE 12. Address Selection ADR Slave Address Write (8 bits) Slave Address Read (8 bits) 0 1 01011000 (58H) 01011010 (5AH) 01011001 (59H) 01011011 (5BH) Before any data is transmitted, the master transmits the address of the slave being addressed. The slave device should send an acknowledge signal on the SDA line, once it recognizes its address. The slave address is the first seven bits after a Start Condition. The direction of the data transfer (R/W) depends on the bit sent after the slave address -- the eighth bit. When the slave address is sent, each device in the system compares this slave address with its own. If there is a match, the device considers itself addressed and sends an acknowledge signal. Depending upon the state of the R/W bit (1:read, 0:write), the device acts as a transmitter or a receiver. TABLE 13. Data Read and Write Cycles Address Mode Data Read <Start Condition> <Slave Address><r/w = 0>[Ack] <Register Addr.>[Ack] <Repeated Start Condition> <Slave Address><r/w = 1>[Ack] [Register Data]<Ack or NAck> ... additional reads from subsequent register address possible <Stop Condition> Data Write <Start Condition> <Slave Address><r/w='0'>[Ack] <Register Addr.>[Ack] <Register Data>[Ack] ... additional writes to subsequent register address possible <Stop Condition> I2C Chip Address 30085851 Control Register Write Cycle * Master device generates start condition. * Master device sends slave address (7 bits) and the data direction bit (r/w = 0). * Slave device sends acknowledge signal if the slave address is correct. * Master sends control register address (8 bits). * Slave sends acknowledge signal. * Master sends data byte to be written to the addressed register. * Slave sends acknowledge signal. * If master will send further data bytes the control register address will be incremented by one after acknowledge signal. * Write cycle ends when the master creates stop condition. <>Data from master [ ] Data from slave 27 www.ti.com LP8543 There is one exception to the "acknowledge after every byte" rule. When the master is the receiver, it must indicate to the transmitter an end of data by not-acknowledging ("negative acknowledge") the last byte clocked out of the slave. This "negative acknowledge" still includes the acknowledge clock pulse (generated by the master), but the SDA line is not pulled down. LP8543 Register Read and Write Detail 30085894 30085895 www.ti.com 28 Inductor Selection A 15 H shielded inductor is suggested for LP8543 boost converter. Inductor maximum current can be calculated from the equations below. As a result the inductor should be selected according to the ISAT. A more conservative and recommended approach is to choose an inductor that has a saturation current rating greater than the maximum current limit of 0.9...2.5A (programmed to EEPROM). Maximum current limit needed for the application can be approximated with calculations above. A 15 H inductor with a saturation current rating of 2.5A is recommended for most applications. The inductor's resistance should be less than 300 m for good efficiency. For high efficiency choose an inductor with high frequency core material such as ferrite to reduce core losses. To minimize radiated noise, use shielded core inductor. Inductor should be placed as close to the SW pin and the IC as possible. Special care should be used when designing the PCB layout to minimize radiated noise and to get good performance from the boost converter. * IRIPPLE: Average to peak inductor current * IOUTMAX: Maximum load current * VIN: Maximum input voltage in application * L: Min inductor value including worst case tolerances * f: Minimum switching frequency * VOUT: Output voltage OUTPUT CAPACITOR A ceramic capacitor with 50V voltage rating or higher is recommended for the output capacitor. The DC-bias effect can reduce the effective capacitance by up to 80%, which needs to be considered in capacitance value selection. For light loads (<100 mA) 4.7 F capacitor is sufficient. For maximum output voltage/current 10 F capacitor (4 uF effective capacitance @ 38V) is recommended to reduce the output ripple. Small 33 pF capacitor is recommended to use in parallel with the output capacitor to suppress high frequency noise. Example using above equations: * VIN = 12V * VOUT = 38V * IOUT = 400 mA * L = 15 H - 20% = 12 H * f = 1.25 MHz * ISAT = 1.6A LDO CAPACITOR A 470 nF ceramic capacitor with 10V voltage rating is recommended for the LDO capacitor. OUTPUT DIODE A schottky diode should be used for the output diode. Peak repetitive current should be greater than inductor peak current (0.9...2.5A) to ensure reliable operation. Average current rating should be greater than the maximum output current. Schottky diodes with a low forward drop and fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse breakdown voltage of the Schottky diode significantly larger (~60V) than the output voltage. Do not use ordinary rectifier diodes, since slow switching speeds and long recovery times cause the efficiency and the load regulation to suffer. AMBIENT LIGHT SENSOR LP8543 uses light-to-frequency type ambient light sensor. Suitable frequency range for ALS is 200 Hz to 2 MHz. 29 www.ti.com LP8543 Recommended External Components www.ti.com 30 Fault TEMP MSB TEMP LSB EEPROM_control 0CH 0DH 0EH 72H ALS LSB Display2 PWM 08H 0BH Boost Control 07H Config2 Display2 Current 06H ALS MSB Display1 Current 05H 09H Output Control 04H 0AH Status Identification 01H 03H Config1 00H 02H REGISTER Display1 PWM ADDR D7 D6 BOOST_AUTO EE_READY TEMP[2:0] DISP2_FAULT DISP1_FAULT ALS[1:0] LED_PANEL LP8543 Register Map LED_OPEN EN_BOOST D3 NSTBY UVLO EE_UPDATE TEMP[10:3] LED_SHORT ALS[9:2] CURRENT_SEL DISP2_PWM[7:0] DISP2_CURRENT[7:0] DISP1_CURRENT[7:0] OUT[7:1] BL_STAT DISP1_PWM[7:0] D4 1_CH_SD MFG[3:0] 2_CH_SD D5 EE_ERASE ALS_SEL VPROG[4:0] OV_CURR PWM_MD D2 EE_PROG ALS_CALC_EN REV[2:0] THRM_SHDN PWM_SEL D1 EE_READ ALS_EN FAULT BL_CTL D0 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0110 0000 0000 0000 0000 0000 0000 0000 1111 1001 0000 0000 0000 0000 1111 1111 DEFAULT LP8543 SLOPE_SEL[1:0] D6 D5 D4 PWM A3[7:0] PWM B3[7:0] DISP1_CURRENT[7:0] DISP2_CURRENT[7:0] AEH AFH B0H B1H BFH BEH BDH ALS_PRESCALE[1:0] Reserved Reserved IMAX_SEL[1:0] Reserved ALS_PRESCALE[9:2] Reserved Reserved VPROG[4:0] Reserved Reserved 00H DRV_HEADR_CTRL[2:0] Reserved BCH LED_FAULT_THR[2:0] Reserved BAH BBH 00H Reserved 00H 7AH 7CH 90H 00H 00H 00H 00H BCH 45H Reserved DIG_COMP[1:0] FILTER_TIME PSPWM_FREQ[1:0] DISABLE_PS B9H BOOST_MODE B8H PWM_FREQ[2:0] EN_AUTOLOAD Reserved BOOST_UP[1:0] reserved 21H A4H B7H PWM_MODE B5H EN_STANDALONE FAULT_SEL[1:0] 62H 62H FFH 00H FFH FFH 00H 40H Reserved reserved B4H TEMP_LIM[1:0] 00H FFH B6H EN_SLOPE B3H DIS_TEMP_CALC PWM THR2[7:0] ADH EN_DISP2_MON PWM B2[7:0] reserved PWM A2[7:0] ABH ACH UVLO_THR PWM THR1[7:0] AAH ALS_EN PWM B1[7:0] A9H OUTPUT_CONF[1:0] 00H PWM A1[7:0] A8H B2H FFH ALS B3[7:0] A7H FFH ALS A3[7:0] A6H FFH 00H FFH 0AH 3DH DEFAULT ALS B2[7:0] BOOST_FREQ D0 ALS THR2[7:0] ALSO_POLARITY D1 A5H ALS A2[7:0] A3H D2 A4H ALS B1[7:0] ALS THR[7:0] A2H D3 A1H ALS A1[7:0] D7 A0H ADDR LP8543 EEPROM Memory Map LP8543 31 www.ti.com LP8543 www.ti.com 32 LP8543 Physical Dimensions inches (millimeters) unless otherwise noted SQA24A: LLP-24, 0.5mm pitch, no pullback 33 www.ti.com LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight Notes TI/NATIONAL INTERIM IMPORTANT NOTICE Texas Instruments has purchased National Semiconductor. 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Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP(R) Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page www.ti.com/video e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2011, Texas Instruments Incorporated