Programmable Current Backlight Driver with Ambient Light Sensor Input ADP5501 TYPICAL OPERATING CIRCUIT 1µF 2.7V TO 5.5V 1µF 4.7µH 2 1 PGND SW 21 VBAT 16 VDDIO 5 SCL 4 SDA 3 INT 15 RST 2.2kΩ 10kΩ 2.2kΩ I/O RAIL 10kΩ Efficient asynchronous boost converter for driving up to 6 white LEDs 2.7 V to 5.5 V input voltage range 128 programmable backlight LED current levels (30 mA maximum) Programmable backlight fade-in/fade-out times Programmable backlight dim and off times Ambient light sensing with autonomous backlight adjustment 3 auxiliary LED current sinks 64 programmable auxiliary LED current levels (14 mA maximum) Programmable auxiliary LED fade-in/fade-out times Programmable auxiliary LED on and off times (allows blinking) I2C-compatible serial interface Interrupt line for signaling an external processor (INT) Hard reset (RST) Current limit protection Thermal overload protection Available in small 4.0 mm × 4.0 mm, 24-lead LFCSP package 22 23 BST BL_SNK CAP_OUT 20 1µF GND 19 GND 24 100nF CMP_IN 17 RGB NC NC NC NC NC NC 6 GND 18 ADP5501 7 8 9 10 11 LED1 LED2 LED0 12 13 14 VBAT 3.3V Figure 1. APPLICATIONS Display backlight driver with ambient light sensor input and control and multiple LED indicator sinks GENERAL DESCRIPTION The ADP5501 is a versatile, single-chip, white LED backlight driver with programmable ambient light sensor input and programmable LED current. This device is designed for mediaenabled handset applications. The ADP5501 uses an I2C®compatible serial interface and a single line interrupt to communicate with the host processor. The ADP5501 can detect ambient light levels and adjust the backlight brightness accordingly, resulting in extended battery life. Once configured, the ADP5501 is capable of controlling the display backlight intensity, on/off timing, dimming, and fading without the intervention of the main processor, which translates into valuable battery power savings. The three auxiliary LEDs are also capable of fading and are timed on and off via register programming. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2008 Analog Devices, Inc. All rights reserved. 07780-001 FEATURES ADP5501 TABLE OF CONTENTS Features .............................................................................................. 1 Fade Override ............................................................................. 13 Applications ....................................................................................... 1 Advanced Fading (Square) ........................................................ 13 Typical Operating Circuit ................................................................ 1 Advanced Fading (Cubic 1 and Cubic 2) ................................ 13 General Description ......................................................................... 1 Ambient Light Sensing .............................................................. 14 Revision History ............................................................................... 2 Automatic Backlight Adjustment ............................................. 14 Specifications..................................................................................... 3 LED Current Sinks ..................................................................... 15 Absolute Maximum Ratings............................................................ 5 Interrupt Output (INT) ............................................................. 17 Thermal Resistance ...................................................................... 5 Reset Input (RST) ....................................................................... 17 ESD Caution .................................................................................. 5 Communicaton Interface .............................................................. 18 Pin Configuration and Function Descriptions ............................. 6 Register Map ................................................................................... 19 Typical Performance Characteristics ............................................. 7 Detailed Register Descriptions ..................................................... 20 Theory of Operation ........................................................................ 9 Applications Information .............................................................. 26 Backlight Drive Control .............................................................. 9 Converter Topology ................................................................... 26 Backlight Operating Levels ....................................................... 10 PCB Layout ................................................................................. 27 Backlight Maximum and Dim Settings ................................... 10 Example Circuit .......................................................................... 27 Backlight Turn-On/Turn-Off/Dim .......................................... 10 Outline Dimensions ....................................................................... 28 Automatic Dim and Turn-Off Timers ..................................... 11 Ordering Guide .......................................................................... 28 Linear Backlight Fade-In and Fade-Out.................................. 11 REVISION HISTORY 10/08—Revision 0: Initial Version Rev. 0 | Page 2 of 28 ADP5501 SPECIFICATIONS VBAT = 2.7 V to 5.5 V, TJ = −400C to +1250C, unless otherwise noted. Table 1. Parameter SUPPLY VOLTAGE VBAT Input Voltage Range VDDIO Input Voltage Range Undervoltage Lockout Threshold SW Leakage SUPPLY CURRENT Shutdown Current3 Standby Current4 Conditions1 Symbol VBAT VIO UVLOVBAT UVLOVBAT UVLOVDDIO UVLOVDDIO SWLEAKAGE VBAT falling VBAT rising VDDIO falling VDDIO rising 2.7 V ≤ VBAT ≤ 5.5 V ISD ISTNBY OPEN-DRAIN OUTPUT LOGIC LEVELS (INT, SDA) Logic Low Output Voltage Logic High Leakage Current AUX LED CURRENT SINKs (ILED, C3, R3) Leakage Full-Scale Current Sink THERMAL SHUTDOWN Thermal Shutdown Threshold Thermal Shutdown Hysteresis I2C TIMING SPECIFICATIONS Delay from Reset Deassertion to I2C Access SCL Clock Frequency SCL High Time SCL Low Time Data Setup Time Data Hold Time Setup Time for Repeated Start 2.7 1.8 1.7 Backlight code = 0x7F, bias = 0.65 V Fade timers disabled BLFULLSCALE 1.8 V ≤ VDDIO ≤ 3.3 V2 1.8 V ≤ VDDIO ≤ 3.3 V2 1.8 V ≤ VDDIO ≤ 3.3 V2 VOL VOH-LEAKAGE ISINK = 1mA 1.8 V ≤ VDDIO ≤ 3.3 V2 LEDLEAKAGE LEDFULLSCALE Sink disabled Applied pin voltage = 1 V TS TSHYS TJ rising TJ falling Max Unit 5.5 3.32 2.1 2.4 1.3 1.4 0.1 1 0.1 25 1 45 μA μA 450 200 24.5 600 200 27 1 750 400 29.5 mA mΩ V mS 26 30 32 mA 1.1 2.7 0.3 0.7 VIL VIH VI-LEAKAGE VIL-DBNC Typ V V V V V V μA VDDIO = 0 V 1.8 V ≤ VDDIO ≤ 3.3 V2, STNBY = 0 BACKLIGHT LED DRIVER (SW, BST) Current Limit (Peak Inductor Current) On Resistance Overvoltage Threshold Boost Startup Time BACKLIGHT LED CURRENT SINK (BL_SNK) Full-Scale Current Sink Backlight Current Ramp Rate AMBIENT LIGHT SENSOR (CMP_IN) Full-Scale Current INPUT LOGIC LEVELS (SCL, SDA, RST) Logic Low Input Voltage Logic High Input Voltage Input Leakage Current INPUT LOGIC DEBOUNCE (RST) Min 1 mA/ms 1.2 mA 0.3 × VDDIO 0.1 75 1 100 V V μA μs 0.1 0.4 1 V μA 0.1 14 1 16.5 μA mA 0.7 × VDDIO 50 10.5 150 10 °C °C 60 fSCL tHIGH tLOW tSU, DAT tHD, DAT tSU, STA 400 0.6 1.3 100 0 0.6 Rev. 0 | Page 3 of 28 0.9 μs kHz μs μs ns μs μs ADP5501 Parameter Hold Time for Start/Repeated Start Bus Free Time for Stop and Start Condition Setup Time for Stop Condition Rise Time for SCL and SDA Fall Time for SCL and SDA Pulse Width of Suppressed Spike Capacitive Load for Each Bus Line Symbol tHD, STA tBUF tSU, STO tR tF tSP CB 5 Conditions 1 Min 0.6 1.3 0.6 20 + 0.1 CB 20 + 0.1 CB 0 Typ Max Unit μs μs μs ns ns μs pF 300 300 50 400 1 All limits at temperature extremes are guaranteed via correlation using standard statistical quality control (SQC). Typical values are at TA = 25°C, VBAT = 3.6 V. 3.3 V or VBAT, whichever is smaller. Internal LDO powered down, digital blocks inactive, I2C inactive, boost inactive. 4 Internal LDO powered up, digital blocks active, I2C active, boost inactive. 5 CB is the total capacitance of one bus line in picofarads (pF). 2 3 SDA tLOW tR tF tSU, DAT tF tHD, STA tSP tBUF tR SCL S tHD, DAT tHIGH tSU, STA Sr P S 07780-002 S = START CONDITION Sr = REPEATED START CONDITION P = STOP CONDITION tSU, STO Figure 2. Interface Timing Diagram Rev. 0 | Page 4 of 28 ADP5501 ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings apply individually only, not in combination. Unless otherwise specified, all other voltages are referenced to GND. Table 2. Parameter VBAT to GND VDDIO to GND SW/BST to GND LED0/LED1/LED2/CMP_IN/SCL/SDA/INT/ RST/CAP_OUT/BL_SNK to GND PGND to GND Operating Ambient Temperature Range Operating Junction Temperature Range Storage Temperature Range Soldering Conditions 1 Rating –0.3 V to +6 V –0.3 V to VBAT –0.3 V to +30 V –0.3 V to +6 V THERMAL RESISTANCE θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. –0.3 V to +0.3 V −40°C to +85°C1 –40°C to +125°C –65°C to +150°C JEDEC J-STD-020 In applications where high power dissipation and poor thermal resistance are present, the maximum ambient temperature may have to be derated. Maximum ambient temperature (TA(MAX)) is dependent on the maximum operating junction temperature (TJ(MAXOP) = 125°C), the maximum power dissipation of the device (PD(MAX)), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), using the following equation: TA(MAX) = TJ(MAXOP) – (θJA x PD(MAX)). Table 3. Thermal Resistance Package Type 24-Lead LFCSP_VQ ESD CAUTION Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rev. 0 | Page 5 of 28 θJA 50 Unit ⁰C/W ADP5501 24 23 22 21 20 19 GND BL_SNK BST VBAT CAP_OUT GND PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 1 2 3 4 5 6 PIN 1 INDICATOR ADP5501 TOP VIEW (Not to Scale) 18 17 16 15 14 13 GND CMP_IN VDDIO RST LED0 LED2 NOTES 1. NC = NO CONNECT. 2. EXPOSED PAD MUST BE CONNECTED TO GROUND. 07780-003 NC NC NC NC NC LED1 7 8 9 10 11 12 PGND SW INT SDA SCL NC Figure 3. Pin Configuration Table 4. Pin Function Descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Mnemonic PGND SW INT SDA SCL NC NC NC NC NC NC LED1 LED2 LED0 RST 16 VDDIO 17 18 19 20 CMP_IN GND GND CAP_OUT 21 22 23 24 VBAT BST BL_SNK GND EPAD Description Power Switch Output to Ground. Power Switch Input. Processor Interrupt, Active Low, Open Drain. INT should be pulled up to VDDIO. I2C-Compatible Serial Data Line (Open Drain Requires External Pull-Up) to VDDIO. I2C-Compatible Serial Clock Line (Open Drain Requires External Pull-Up) to VDDIO. No Connect. No Connect. No Connect. No Connect. No Connect. No Connect. LED 1 Current Sink. LED1 can be used with LED0 and LED2 as RGB. LED 2 Current Sink. LED2 can be used with LED1 and LED0 as RGB. LED 0 Current Sink. LED0 can be used with LED1 and LED2 as RGB. Reset Input, Active Low. This input signal resets the device to the power-up default conditions. It must be driven low for a minimum of 75 μs (typical) to be valid. Supply Voltage for the I/O Pin. The output pin can be 1.8 V to 3.3 V or VBAT, whichever is smaller. If VDDIO = 0, the device goes into full shutdown mode. Input for Ambient Light Sensing. Ground. Ground. Capacitor for Internal 2.7 V LDO. A 1 μF capacitor must be connected between this pin and ground. Do not use this pin to supply external loads. Main Supply Voltage for the IC (2.7 V to 5.5 V). Overvoltage Monitor Input for the Boost Converter. Backlight Current Sink. Ground. The exposed pad must be connected to ground. Rev. 0 | Page 6 of 28 ADP5501 TYPICAL PERFORMANCE CHARACTERISTICS VBAT = 3.6 V, TA = 25°C, unless otherwise noted. Inductor = LPS4012-472MLB. Schottky rectifier = MBR140SFT1G. 48 90 STANDBY SUPPLY CURRENT (µA) 85 80 EFFICIENCY (%) 75 70 65 60 6 LEDs, 6 LEDs, 6 LEDs, 6 LEDs, 55 50 VBAT VBAT VBAT VBAT = 3.0V = 3.6V = 4.2V = 5.5V TEMP = –40°C 40 TEMP = +25°C 32 24 16 TEMP = +85°C 8 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 BACKLIGHT CURRENT (mA) 30 0 2.5 07780-004 Figure 4. Efficiency vs. Backlight Current (6 LEDs) AUX LED FULL-SCALE SINK CURRENT (mA) 80 EFFICIENCY (%) 75 70 65 6 LEDs, VBAT = 3.6V 5 LEDs, VBAT = 3.6V 4 LEDs, VBAT = 3.6V 60 55 50 45 2 4 6 8 10 12 14 16 18 20 22 24 26 28 BACKLIGHT CURRENT (mA) 30 5.0 5.5 6.0 85 80 75 6 LEDs, VBAT = 4.2V 6 LEDs, VBAT = 4.2V, AUTOLOAD-ENABLED 65 60 55 50 2 4 6 8 10 12 14 16 18 20 22 24 26 28 BACKLIGHT CURRENT (mA) 30 07780-006 45 0 12 10 8 6 4 2 0 0.5 1.0 1.5 2.0 AUX LED PIN VOLTAGE (V) 2.5 3.0 Figure 8. Typical Auxiliary LED Pin (LED0, LED1, LED2), Full-Scale Sink Current vs. Applied Pin Voltage 90 70 14 0 07780-005 0 Figure 5. Efficiency vs. Backlight Current (4, 5, and 6 LEDs) EFFICIENCY (%) 4.0 4.5 VBAT (V) 16 85 40 3.5 Figure 7. Standby Supply Current vs. VBAT 90 40 3.0 Figure 6. Efficiency vs. Backlight Current (Autoload On/Off) Rev. 0 | Page 7 of 28 07780-008 40 07780-007 45 ADP5501 SW SW 1 1 INDUCTOR CURRENT INDUCTOR CURRENT 2 2 BST CH1 20.0V CH3 10.0V 3 CH2 500mA CH4 1.0V TIME (4µs/DIV) 4 BL_SNK CH1 20.0V CH3 10.0V Figure 9. Boost Operation (Backlight = 30 mA) CH2 500mA CH4 1.0V TIME (4µs/DIV) 07780-011 4 BL_SNK 07780-009 3 BST Figure 11. Boost Operation (Backlight = 2 mA) SW SW 1 1 INDUCTOR CURRENT INDUCTOR CURRENT 2 2 BST BST 3 BL_SNK 3 CH2 500mA CH4 1.0V TIME (4µs/DIV) 4 07780-010 CH1 20.0V CH3 10.0V Figure 10. Boost Operation (Backlight = 15 mA) CH1 10.0V CH3 10.0V CH2 500mA CH4 1.0V TIME (1ms/DIV) Figure 12. Boost Startup Rev. 0 | Page 8 of 28 07780-012 BL_SNK 4 ADP5501 THEORY OF OPERATION 1µF 2.7V TO 5.5V 1µF 4.7µH 2 SW 22 BST BL_SNK 23 THERMAL PROTECTION I-LIMIT OVP 27V PGND VBAT POR EN BACKLIGHT CURRENT CONTROL FB 0.65V IN 21 VDDIO 16 CAP_OUT BOOST CONTROL 1 LDO OUT 1µF VBAT STATE MACHINE 20 2.7V LIGHT SENSOR REGISTER MAP BIAS/CLOCK SCL 5 LED CURRENT CONTROL INTERFACE INT 3 RST 15 CMP_IN 100nF INTERRUPT/RESET CONTROL SDA 4 17 ADP5501 GND GND GND 19 24 6 7 8 9 10 11 13 NC NC NC NC NC NC 12 14 07780-013 18 LED2 LED1 LED0 Figure 13. Internal Block Diagram The ADP5501 is an autonomous backlight white LED driver with programmable current and ambient light sensor input. It is ideal for cellular phone designs and other portable devices, where programmable and automated light output is needed. Its versatility makes it ideal for media-enabled mobile devices. Programmable fade-in, fade-out, dim, and off timers provide the backlight with excellent flexibility and control features. Using an external photodiode, the ADP5501 can perform ambient light sensing and adjust the backlight brightness according to varying lighting conditions. Programmable fading is also available for the three LED sinks. Once programmed through its I2C-compatible interface, the ADP5501 can run autonomously. An interrupt line (INT) is available to alert an external microprocessor of the status of its ambient light sensor comparator states, current limit, thermal overload, and overvoltage conditions. To achieve this high voltage, the ADP5501 contains a nonsynchronous boost device capable of driving an LED string with an OVP limited to 24.5 V(minimum). For detailed information about the boost device, see the Applications Information section. With sufficient forward voltage created, the ADP5501 controls the current (and thus the brightness) of the LED string via an adjustable internal current sink. An internal state machine, in conjunction with programmable timers, dynamically adjusts the current sink between 0 mA and 30 mA to achieve impressive backlight control features. BST DAYLIGHT_MAX DAYLIGHT_DIM OFFICE_MAX OFFICE_DIM BACKLIGHT DRIVE CONTROL BL_SNK BL_VALUE MUX BL_EN DARK_MAX Rev. 0 | Page 9 of 28 DARK_DIM BL_LVL BL_OFFT BL_DIMT DIM_EN BL_LAW BL_FI BL_FO CLOCK GENERATOR 07780-014 White LEDs are common in backlighting the displays of modern portable devices such as cell phones. White LEDs require a high forward voltage, VF (typically, 3.5 V), before they conduct current and emit light. Display panels, depending on their size, can be backlit with single or multiple white LEDs. In panels that require multiple LEDs, the LEDs are commonly connected in a series string to achieve uniform brightness in each LED by passing a common current through all of them. The LED string, however, needs to be biased with a voltage greater than the sum of each LED VF before it can conduct. COUNTERS AND CONTROL LOGIC Figure 14. Backlight Brightness Control ADP5501 The ADP5501 can also implement a nonlinear (square approximation) relationship between input code and backlight current level. In this case (BL_LAW = 01), the backlight current, in milliamperes (mA), is determined by the following equation: BACKLIGHT OPERATING LEVELS Backlight brightness control can operate in three distinct levels: daylight (L1), office (L2), and dark (L3). The BL_LVL bits in Register 0x02 control the level at which the backlight operates. The BL_LVL bits can be changed manually or, if in auto mode, by the ambient light sensor (see the Ambient Light Sensing section). By default, the backlight operates at daylight level (BL_LVL = 00), where the maximum brightness is set using Register 0x05 (DAYLIGHT_MAX). A daylight dim setting can also be set using Register 0x06 (DAYLIGHT_DIM). When operating at office level (BL_LVL = 01), the backlight maximum and dim brightness settings are set by Register 0x07 (OFFICE_MAX) and Register 0x08 (OFFICE_DIM). When operating at dark level (BL_LVL = 10), the backlight maximum and dim brightness settings are set by Register 0x09 (DARK_MAX) and Register 0x0A (DARK_DIM). OFFICE (L2) 2 (2) 30 25 DARK (L3) DAYLIGHT_MAX 20 15 LINEAR 10 SQUARE 5 OFFICE_MAX DARK_MAX 0 0 32 DAYLIGHT_DIM OFFICE_DIM 64 SINK CODE 96 128 07780-016 BACKLIGHT CURRENT ⎞ ⎟ ⎟ ⎠ Figure 16 shows the backlight current level vs. input code for both the linear and square law algorithms. BACKLIGHT CURRENT (mA) 30mA DAYLIGHT (L1) ⎛ Fullscale _ Current Backlight Current = ⎜ Code × ⎜ 127 ⎝ Figure 16. Backlight Current vs. Sink Code DARK_DIM 07780-015 BACKLIGHT TURN-ON/TURN-OFF/DIM 0 BACKLIGHT OPERATING LEVELS Figure 15. Backlight Operating Levels BACKLIGHT MAXIMUM AND DIM SETTINGS The backlight maximum and dim current settings are determined by a 7-bit code programmed by the user into the registers listed in the Backlight Operating Levels section. This 7-bit code allows the user to set the backlight to one of 128 different levels between 0 mA and 30 mA. The ADP5501 can implement two distinct algorithms to achieve a linear and a nonlinear relationship between input code and backlight current. The BL_LAW bits, in Register 0x02, are used to swap between algorithms. With the device in normal mode (set in Register 0x00 by STNBY = 1), the backlight can be turned on using the BL_EN bit in Register 0x00. Before turning on the backlight, the user should choose the level (daylight (L1), office (L2), or dark (L3)) to operate in and ensure that maximum and dim settings are programmed for that level. The backlight turns on when BL_EN = 1. The backlight turns off when BL_EN = 0. BACKLIGHT CURRENT MAX Backlight Current = Code × (Fullscale_Current/127) where: Code is the input code programmed by the user. Fullscale_Current is the maximum sink current allowed (typically, 30 mA). (1) BL_EN = 1 BL_EN = 0 07780-017 By default, the ADP5501 uses a linear algorithm (BL_LAW = 00), where the backlight current increases linearly for a corresponding increase of input code. Backlight current, in milliamperes (mA), is determined by the following equation: Figure 17. Backlight Turn-On/Turn-Off While the backlight is on (BL_EN = 1), the user can change it to a dim setting by programming DIM_EN = 1 in Register 0x00. If DIM_EN = 0, the backlight reverts to its maximum setting. Rev. 0 | Page 10 of 28 ADP5501 BACKLIGHT CURRENT program the off timer before turning on the backlight. If BL_EN = 1, the backlight turns on to its maximum setting, and the off timer starts counting. When the off timer expires, the internal state machine clears the BL_EN bit, and the backlight turns off. MAX BACKLIGHT CURRENT OFF TIMER RUNNING DIM BL_EN = 1 DIM_EN = 1 DIM_EN = 0 BL_EN = 0 07780-018 MAX The maximum and dim settings can be set between 0 mA and 30 mA; therefore, it is possible to program a dim setting that is greater than a maximum setting. For normal expected operation, the user should program the dim setting to less than the maximum setting. BL_EN = 1 BL_EN = 0 SET BY USER SET BY INTERNAL STATE MACHINE Figure 20. Off Time AUTOMATIC DIM AND TURN-OFF TIMERS The user can program the backlight to dim automatically by using the BL_DIMT timer in Register 0x03. The dim timer has 15 settings ranging from 10 sec to 2 min. The user should program the dim timer before turning on the backlight. If BL_EN = 1, the backlight turns on to its maximum setting, and the dim timer starts counting. When the dim timer expires, the internal state machine sets DIM_EN = 1, and the backlight goes to its dim setting. BACKLIGHT CURRENT DIM TIMER RUNNING 07780-020 Figure 18. Backlight Turn-On/Turn-Off/Dim DIM TIMER RUNNING Reasserting BL_EN at any point during the off timer countdown causes the timer to reset and begin counting again. The backlight can be turned off at any point during the off timer countdown by clearing BL_EN. The dim timer and off timer can be used together for sequential maximum-to-dim-to-off functionality. With both the dim and off timers programmed, if BL_EN is asserted, the backlight turns on to its maximum setting. When the dim timer expires, the backlight changes to its dim setting. When the off timer expires, the backlight turns off. BACKLIGHT CURRENT MAX DIM TIMER RUNNING MAX OFF TIMER RUNNING DIM DIM SET BY USER SET BY INTERNAL STATEMACHINE BL_EN = 0 BL_EN = 1 Figure 19. Dim Timer If the user clears the DIM_EN bit (or reasserts the BL_EN bit), the backlight reverts to its maximum setting, and the dim timer begins counting again. When the dim timer expires, the internal state machine again sets DIM_EN = 1, and the backlight goes to its dim setting. Reasserting BL_EN at any point during the dim timer countdown causes the timer to reset and begin counting again. The backlight can be turned off at any point during the dim timer countdown by clearing BL_EN. DIM_EN = 1 BL_EN = 0 SET BY USER SET BY INTERNAL STATE MACHINE 07780-021 DIM_EN = 0 DIM_EN = 1 OR BL_EN = 1 07780-019 BL_EN = 1 DIM_EN = 1 Figure 21. Dim and Off Timers Used Together LINEAR BACKLIGHT FADE-IN AND FADE-OUT To counteract the abrupt effect on the eyes of near instant turnon and turn-off of the backlight, the ADP5501 contains timers to facilitate smooth fading among the off, on, and dim states. By default (BL_LAW = 00 in Register 0x02), the ADP5501 implements a fading scheme using the linear backlight code algorithm (see Equation 1). The user can also program the backlight to turn off automatically by using the BL_OFFT timer in Register 0x03. The off timer has 15 settings ranging from 10 sec to 2 min. The user should Rev. 0 | Page 11 of 28 ADP5501 The BL_FI timer in Register 0x04 can be used for smooth fadein transitions from low to high backlight settings such as off to dim, off to maximum, and dim to maximum. The BL_FI timer can be programmed to one of 15 settings ranging from 0.3 sec to 5.5 sec. The BL_FI timer should be programmed before asserting BL_EN. BACKLIGHT CURRENT FADE-IN OFF-TO-MAX FADE-OUT MAX-TO-DIM FADE-OUT FADE-IN FADE-IN FADE-OUT MAX FADE-OUT DIM-TO-OFF DIM 30.0 27.5 17.5 15.0 12.5 10.0 7.5 5.0 2.5 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 FADE-IN TIME (Sec) 4.0 4.5 5.0 5.5 BL_EN = 1 DIM_EN = 1 BL_EN = 0 The time programmed in BL_FI represents the time it takes the backlight current to go from 0 mA to 30 mA. Fading between intermediate settings is shorter. The BL_FO timer in Register 0x04 can be used for smooth fadeout transitions from high to low backlight settings such as maximum to dim and dim to off. The BL_FO timer can be programmed to one of 15 settings ranging from 0.3 sec to 5.5 sec. The BL_FO timer should be programmed before asserting BL_EN. Figure 24 shows the fade timers in use. With BL_FI and BL_FO programmed, if BL_EN is asserted, the backlight fades in to its maximum setting. If DIM_EN is asserted, the backlight fades out to its dim setting. If BL_EN is cleared, the backlight fades out to off. During any point in a fade-out, if BL_EN is asserted, the backlight stops at its current fade-out position and begins fading in. The fade-in and fade-out timers can be used independently of each other; that is, fade-in can be enabled while fade-out is disabled. The fade timers can also be used with the off and dim timers. Figure 25 shows the fade timers used with the dim and off timers. BACKLIGHT CURRENT BACKLIGHT CURRENT (mA) 20.0 17.5 15.0 12.5 10.0 7.5 FADE-OUT MAX 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 22.5 OFF TIMER RUNNING FADE-OUT DIM BL_EN = 1 DIM_EN = 1 SET BY USER SET BY INTERNAL STATE MACHINE 5.0 2.5 BL_EN = 0 DIM_EN = 0 Figure 25. Fade/Dim/Off Timers Used Together 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 FADE-OUT TIME (Sec) 4.5 5.0 5.5 07780-023 0 DIM TIMER RUNNING FADE-IN 30.0 25.0 BL_EN = 0 BL_EN = 1 Figure 24. Backlight Turn-On/Turn-Off/Dim with Fade Timers Figure 22. Linear Fade-In Times 27.5 BL_EN = 0 BL_EN = 1 07780-024 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 20.0 Figure 23. Linear Fade-Out Times The time programmed in BL_FO represents the time it takes the backlight current to go from 30 mA to 0 mA. Fading between intermediate settings is shorter. Rev. 0 | Page 12 of 28 07780-025 22.5 07780-022 BACKLIGHT CURRENT (mA) 25.0 ADP5501 30.0 FADE OVERRIDE BACKLIGHT CURRENT FADE-IN OVERRIDDEN FADE-OUT OVERRIDDEN MAX 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 27.5 25.0 BACKLIGHT CURRENT (mA) A fade override feature allows the BL_FI and BL_FO timers to be overridden when the BL_EN bit is reasserted (by the user setting the FOVR bit in Register 0x02) during a fade-in or fadeout period and to set the backlight to its maximum setting. 22.5 20.0 17.5 15.0 12.5 10.0 7.5 5.0 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 FADE-OUT TIME (Sec) 4.5 5.0 5.5 07780-028 2.5 Figure 28. Square Law Fade-Out Times ADVANCED FADING (CUBIC 1 AND CUBIC 2) BL_EN = 0 BL_EN = 0 07780-026 BL_EN = 1 BL_EN = 1 BL_EN = 1 (REASSERTED BY USER ) (REASSERTED BY USER) Figure 26. Fade Override ADVANCED FADING (SQUARE) Although the default linear fade algorithm gives a smooth increase and decrease in backlight current, the resulting increase and decrease in brightness still appear visually abrupt. For example, for a given fade-in time, the eye notices an initial increase in brightness as backlight current is increased but cannot perceive much more increase in brightness as backlight current is increased to maximum. The reason for this is that the eye perceives changes in light when the brightness of the light source is changed logarithmically (Weber-Fechner law). To provide a more natural fading experience to the user, the fade timers can be used in conjunction with the square law approximation backlight codes (see Equation 2) by setting BL_LAW = 01 in Register 0x02. Cubic fading is implemented by re-using the square algorithm codes but ramping them with a clock source whose frequency output increases as the sink current code increases (see Figure 29). Cubic 1 and Cubic 2 have different frequency vs. code characteristics. BST BL_SNK DAYLIGHT_MAX DAYLIGHT_DIM OFFICE_MAX 30.0 OFFICE_DIM 27.5 DARK_MAX DARK_DIM 25.0 22.5 BL_LVL 20.0 BL_VALUE MUX BL_EN BL_OFFT BL_DIMT DIM_EN COUNTERS AND CONTROL LOGIC BL_LAW BL_FI BL_FO 17.5 CLOCK GENERATOR 15.0 10.0 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 7.5 5.0 2.5 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 FADE-IN TIME (Sec) 4.0 4.5 5.0 5.5 07780-029 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 12.5 Figure 29. Backlight Brightness Control (Cubic) 07780-027 BACKLIGHT CURRENT (mA) Two additional advanced settings in Register 0x02 are available for fading the backlight brightness levels, Cubic 1 (BL_LAW = 10) and Cubic 2 (BL_LAW = 11). As shown in the backlight brightness control block diagram in Figure 14, linear fading and square fading are implemented by ramping the 128 linear/square algorithm codes at a fixed frequency over the duration of a given fade-in/fade-out time. Figure 27. Square Law Fade-In Times Rev. 0 | Page 13 of 28 ADP5501 Figure 30 shows a comparison of fading techniques. Cubic fades complete faster than linear or square fades for a given fade time setting. Cubic 1 completes approximately 30% faster, and Cubic 2 completes approximately 10% faster, than an equivalent linear or square fade time. With four fade laws and 15 fade time settings, the user can easily find the right fade experience for an application. 30 L3_CMPR is used to detect when the photosensor output drops below the programmable L3_TRIP point. If this event occurs, the L3_OUT status signal is set. L3_CMPR contains programmable hysteresis, meaning that the photosensor output must rise above L3_TRIP + L3_HYS before L3_OUT is cleared. L3_CMPR is enabled in Register 0x0C via the L3_EN bit. The L3_TRIP and L3_HYS values of L3_CMPR can be set between 0 μA and 127 μA in steps of 0.5 μA (typical). CUBIC 1 L2_TRIP L2_HYS 20 L3_TRIP LINEAR SQUARE L3_HYS 10 CUBIC 2 5 0 1 100 1000 Figure 32. Comparator Ranges 0 0.2 0.4 0.6 UNIT FADE TIME 0.8 1.0 Figure 30. Fade Law Comparison over a Unit Fade Time AMBIENT LIGHT SENSING The ADP5501 can be used in conjunction with an external photosensor to detect when ambient light conditions drop below programmable set points. An ADC samples the output of the external photosensor. The ADC result is fed into two programmable trip comparators. The ADC has an input range of 0 μA to 1000 μA (typical). L2_EN L2_TRIP L2_HYS R MP _C L2 L2_OUT FILTER SETTINGS ADC The L2_CMPR and L3_CMPR comparators can be enabled independently of each other. The ADC and comparators run continuously when L2_EN and/or L3_EN is set during automatic backlight adjustment mode. A single conversion takes 80 ms (typical). Filter times of between 80 ms and 10 sec can be programmed for the comparators before they change state. It is also possible to use the light sensor comparators in a singleshot mode. After the single-shot measurement is completed, the internal state machine clears the FORCE_RD bit in Register 0x0C. The interrupt flag CMPR_INT is set in Register 0x00 if either of the L2_OUT or L3_OUT status bits changes state, meaning that interrupts can be generated if ambient light conditions transition between any of the programmed trip points. CMPR_INT can cause the INT pin to be asserted if the CMPR_IEN bit is set in Register 0x01. The CMPR_INT flag can be cleared only by writing a 1 to it. AUTOMATIC BACKLIGHT ADJUSTMENT L3_TRIP L3_HYS R MP _C L3 L3_OUT L3_EN 07780-031 PHOTO SENSOR OUTPUT 10 ADC RANGE (µA) 07780-032 15 07780-030 BACKLIGHT CURRENT (mA) 25 Figure 31. Ambient Light Sensing and Trip Comparators The Level 2 (office) light sensor comparator, L2_CMPR, is used to detect when the photosensor output drops below the programmable L2_TRIP point. If this event occurs, the L2_OUT status signal is set. L2_CMPR contains programmable hysteresis, meaning that the photosensor output must rise above L2_TRIP + L2_HYS before L2_OUT is cleared. L2_CMPR is enabled in Register 0x0C via the L2_EN bit. The L2_TRIP and L2_HYS values of L2_CMPR can be set between 0 μA and 1000 μA in steps of 4 μA (typical). The ambient light sensor comparators can be used to automatically transition the backlight among its three operating levels. To enable this mode, the BL_AUTO_ADJ bit is set in Register 0x02. Once enabled, the internal state machine takes control of the BL_LVL bits in Register 0x02 and changes them based on the L2_OUT and L3_OUT status bits in Register 0x0C. The L2_OUT status bit indicates that ambient light conditions have dropped below the L2_TRIP point and the backlight should be moved to its office (L2) level. The L3_OUT status bit indicates that ambient light conditions have dropped below the L3_TRIP point and the backlight should be moved to its dark (L3) level. Table 5 shows the relationship between backlight operation and the ambient light sensor comparator outputs. Rev. 0 | Page 14 of 28 ADP5501 BL_AUTO_ADJ 0 L3_OUT X1 L2_OUT X1 1 0 0 1 0 1 1 1 0 1 1 1 1 Backlight Operation BL_LVL can be manually set by the user. BL_LVL = 00; backlight operates at L1 (daylight). BL_LVL = 01; backlight operates at L2 (office). BL_LVL = 10; backlight operates at L3 (dark). BL_LVL = 10; backlight operates at L3 (dark). X = don’t care. The L3_OUT status bit has greater priority; therefore, the backlight operates at L3 (dark) even if L2_OUT is set. LED CURRENT SINKS The ADP5501 has three additional current sinks that can be used as RGBs or auxiliary LED current sinks. Each current sink is programmable up to 14 mA (typical) and can be independently turned on and off. By default, the ADP5501 uses a linear algorithm (LED_LAW = 0 in Register 0x11), where the LED sink current increases linearly for a corresponding increase of input code. The LED sink current, in milliamperes (mA), is determined by the following equation: LED Sink Current = Code × (Fullscale_Current/63) where: Code is the input code programmed by the user. Fullscale_Current is the maximum sink current allowed (typically, 14 mA). The ADP5501 can also implement a nonlinear (square approximation) relationship between input code and LED sink current level. In this case (LED_LAW = 1 in Register 0x11), the LED sink current, in milliamperes (mA), is determined by the following equation: ⎛ Fullscale _ Current LED Sink Current = ⎜ Code × ⎜ 63 ⎝ LED0_EN LED0_OFFT LED 1 DIGITAL COUNTERS AND CONTROL 10 8 LINEAR 6 SQUARE 4 2 0 0 16 VBAT LED1_EN LED1_OFFT 48 VBAT LED1 LED1_CURRENT 32 CODE Figure 33. LED Sink Current vs. Code VBAT LED0_CURRENT (4) 12 These LEDx_CURRENT registers are six bits wide, allowing the user to set the LED sink current to one of 64 different levels between 0 mA and 14 mA. The ADP5501 can implement two distinct algorithms to achieve a linear and a nonlinear relationship between input code and sink current. LED0 2 14 LED SINK CURRENT (mA) The LED2 pin is the current sink for LED2. Its sink current can be set using LED2_CURRENT in Register 0x16. LED2 sink can be enabled with LED2_EN in Register 0x11. ⎞ ⎟ ⎟ ⎠ Figure 33 shows the backlight current level vs. the input code for both the linear and square law algorithms. The LED0 pin is the current sink for LED0. Its sink current can be set using LED0_CURRENT in Register 0x14. LED0 sink can be enabled with LED0_EN in Register 0x11. The LED1 pin is the current sink for LED1. Its sink current can be set using LED1_CURRENT in Register 0x15. LED1 sink can be enabled with LED1_EN in Register 0x11. (3) LED 2 DIGITAL COUNTERS AND CONTROL LED2 LED2_EN LED2_CURRENT LED2_OFFT LED 3 DIGITAL COUNTERS AND CONTROL LED_ONT LED_FI 07780-033 LED_FO LED_LAW Figure 34. Status LED Current Sink Rev. 0 | Page 15 of 28 64 07780-034 Table 5. Comparator Output Truth Table ADP5501 15 12 9 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 3 By default (LED_LAW = 0 in Register 0x11), the ADP5501 implements a fading scheme using the linear algorithm (see Equation 3). 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 6 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 FADE-IN TIME (Sec) 4.0 4.5 5.0 5.5 07780-037 LED SINK CURRENT (mA) Similar to the backlight current sink, the ADP5501 contains timers to facilitate the smooth fading between off and on states of the LED current sinks. All three LED sinks share a common fade-in (LED_FI) timer as well as a common fade-out (LED_FO) timer. The fade-in and fade-out timers are located in Register 0x13 and can be programmed to one of 15 settings ranging from 0.3 sec to 5.5 sec. Fade-in times represent the time it takes to fade from 0 mA to 14 mA. Fade-out times represent the time it takes to fade from 14 mA to 0 mA. Fading between intermediate settings is shorter. The fade timers should be programmed before asserting LEDx_EN in Register 0x11. Figure 37. Square Law Fade-In Times 15 15 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 12 6 3 0.5 1.0 1.5 2.0 2.5 3.0 3.5 FADE-IN TIME (Sec) 4.0 4.5 5.0 5.5 0 Figure 35. Linear Fade-In Times LED SINK CURRENT (mA) 12 9 6 1.0 1.5 2.0 2.5 3.0 3.5 4.0 FADE-OUT TIME (Sec) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 FADE-OUT TIME (Sec) 4.5 5.0 5.5 The LED current sinks have additional timers to facilitate blinking functions. A shared on timer (LED_ONT in Register 0x12) used in conjunction with three off timers (LED0_OFFT, LED1_OFFT, and LED2_OFFT) allows the LED current sinks to be configured in various blinking modes. The on timer can be set to four different settings: 0.2 sec, 0.6 sec, 0.8 sec, and 1.2 sec. The off timers also have four different settings: disabled, 0.6 sec, 0.8 sec, and 1.2 sec. Blink mode is activated by setting the off timers to any setting other than disabled. 5.0 All fade-on and fade-off timers should be programmed before enabling any of the LED current sinks. If LEDx is on during a blink cycle and LEDx_EN is cleared, LEDx goes off (or fades to off if fade-out is enabled). If LEDx is off during a blink cycle and LEDx_EN is cleared, LEDx stays off. 4.5 5.5 07780-036 0.5 0.5 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 3 0 0 Figure 38. Square Law Fade-Out Times 15 0 6 3 0 0 9 07780-038 9 LED SINK CURRENT (mA) 0.3 SEC 0.6 SEC 0.9 SEC 1.2 SEC 1.5 SEC 1.8 SEC 2.1 SEC 2.4 SEC 2.7 SEC 3.0 SEC 3.5 SEC 4.0 SEC 4.5 SEC 5.0 SEC 5.5 SEC 07780-035 LED SINK CURRENT (mA) 12 Figure 36. Linear Fade-Out Times To provide a more natural fading experience for the user, the fade timers can be used in conjunction with the square law approximation codes (see Equation 4) by setting LED_LAW = 1. Rev. 0 | Page 16 of 28 ADP5501 VDDIO LEDx CURRENT FADE-IN ALS COMPARATOR INTERRUPTS ON TIME FADE-OUT FADE-IN FADE-OUT OR MAX OVERVOLTAGE INTERRUPT INT 07780-040 ON TIME Figure 40. INT Pin Drive OFF TIME RESET INPUT (RST) 07780-039 LEDx_EN = 1 OFF TIME The ADP5501 can be restored to a power-on reset state if the RST pin is held low. RST contains a debounce circuit; therefore, the pin must be held low for greater than 75 μs (typical) before a reset occurs. Figure 39. LEDx Blink Mode with Fading INTERRUPT OUTPUT (INT) The ADP5501 can generate interrupts to an external processor via its interrupt output, INT. INT is an active low, open-drain pin that should be pulled up to VDDIO. INT can be asserted by one of several internal blocks, as shown in Figure 40. Rev. 0 | Page 17 of 28 ADP5501 COMMUNICATON INTERFACE Communication with the ADP5501 is done via its I2Ccompatible serial interface. Figure 41 shows a typical write sequence for programming an internal register. 5. 6. 7. 8. 0 = WRITE ST SP 1 1 0 0 1 CHIP ADDRESS 0 0 0 0 0 REGISTER ADDRESS ADP5501 RECEIVES DATA 07780-041 0 ADP5501 ACK Figure 41. I2C Write Sequence 0 = WRITE 1 = READ ST 0 1 1 0 0 1 CHIP ADDRESS 0 0 0 0 REGISTER ADDRESS SP 0 1 1 0 0 1 CHIP ADDRESS Figure 42. I2C Read Sequence Rev. 0 | Page 18 of 28 0 0 1 ADP5501 SENDS DATA 07780-042 ST NO ACK 7. 4. ADP5501 ACK 5. 6. 3. ADP5501 ACK 4. 2. ADP5501 ACK 3. ADP5501 ACK 2. The cycle begins with a start condition, followed by the chip write address (0x64). The ADP5501 acknowledges the chip write address byte by pulling the data line low. The address of the register from which data is to be read is sent next. The ADP5501 acknowledges the register address byte by pulling the data line low. The cycle continues with a repeat start, followed by the chip read address (0x65). The ADP5501 acknowledges the chip read address byte by pulling the data line low. The ADP5501 places the contents of the previously addressed register on the bus for readback. There is a no acknowledge following the readback data byte, and the cycle is completed with a stop condition. 1. The cycle begins with a start condition, followed by the chip write address (0x64). The ADP5501 acknowledges the chip write address byte by pulling the data line low. The address of the register to which data is to be written is sent next. The ADP5501 acknowledges the register address byte by pulling the data line low. The data byte to be written to is sent next. The ADP5501 acknowledges the data byte by pulling the data line low. A stop condition completes the sequence. ADP5501 ACK 1. Figure 42 shows a typical read sequence for reading back an internal register. ADP5501 REGISTER MAP All registers are 0 on reset. Unused bits are read as 0. Table 6. Register Address 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x11 0x12 0x13 0x14 0x15 0x16 Register Name MODE_STATUS INTERRUPT_ENABLE BL_CONTROL BL_TIME BL_FADE DAYLIGHT_MAX DAYLIGHT_DIM OFFICE_MAX OFFICE_DIM DARK_MAX DARK_DIM BL_VALUE ALS_CMPR_CFG L2_TRIP L2_HYS L3_TRIP L3_HYS LED_SINK_CONTROL LED_TIME LED_FADE LED0_CURRENT LED1_CURRENT LED2_CURRENT Register Description Sets the device operating mode; contains enables for backlight on/dim and top level interrupt status bits. Contains enables for allowing interrupts to assert INT. Sets parameters relating to backlight control. Contains backlight off and dim timers. Contains backlight fade-in and fade-out timers. Sets the daylight (L1) maximum current. Sets the daylight (L1) dim current. Sets the office (L2) maximum current. Sets the office (L2) dim current. Sets the dark (L3) maximum current. Sets the dark (L3) dim current. Read-only register of what the backlight is presently set to. Sets enables and filters for ambient light sensor comparators; contains comparator output status bits. Sets the light sensor comparator (L2_CMPR) threshold point. Sets the light sensor comparator (L2_CMPR) hysteresis. Sets the light sensor comparator (L3_CMPR) threshold point. Sets the light sensor comparator (L3_CMPR) hysteresis. Contains enables and configuration for the LED current sinks. Contains the on and off timers for the status LED current sinks. Contains the fade-in and fade-out timers for the status LED current sinks. Sets the LED0 sink current. Sets the LED1 sink current. Sets the LED2 sink current. Rev. 0 | Page 19 of 28 ADP5501 DETAILED REGISTER DESCRIPTIONS Table 7. Register 0x00, Device Mode and Status (MODE_STATUS) Bit 7 Name STNBY R/W R/W 6 BL_EN R/W 5 DIM_EN R/W 41 OVP_INT R/W 31 CMPR_INT R/W 2 to 0 Not used 1 Description 0 = the device is in standby mode. (If 1.8V ≤ VDDIO ≤ 2.7V, then I2C.) 1 = the device is in operating mode. Additional functions such as backlight driver, LED sinks, and ambient light sensor functions can be enabled. 0 = the backlight driver is disabled. 1 = the backlight driver is enabled. 0 = dim mode is disabled. 1 = dim mode is enabled. Dim mode can be enabled in two ways. One is by manually setting this bit, in which case, the backlight stays at a dim level until this bit is manually cleared. The second method is by setting the DIMT timer, in which case, an internal state machine sets this bit and clears it when the timer expires. 0 = no overvoltage protection (OVP) condition. 1 = OVP condition detected. Once set, this bit can be cleared by writing a 1 to it. 0 = no ambient light sensor comparators have triggered. 1 = one of the ambient light sensor comparators has triggered. Once set, this bit can be cleared by writing a 1 to it. If one of the interrupt bits is cleared and there is a pending interrupt, INT deasserts for 50 μs and reasserts, but the status of the pending interrupt stays set. Table 8. Register 0x01, Interrupt Enable (INTERRUPT_ENABLE) Bit 7 to 5 4 Name Not used AUTO_LD_EN R/W Description R/W 3 CMPR_IEN R/W 2 OVP_IEN R/W 0 = autoload is disabled. 1 = autoload is enabled. A 1 mA dummy load turns on when the backlight code is less than 8 (linear law) or less than Code 32 (square law). 0 = ambient light sensor comparator(s) interrupt is disabled. 1 = ambient light sensor comparator(s) interrupt is enabled. 0 = OVP interrupt is disabled. 1 = OVP interrupt is enabled. 1 to 0 Not used Table 9. Register 0x02, Backlight Control (BL_CONTROL) Bit 7 to 6 Name BL_LVL R/W R/W 5 to 4 BL_LAW R/W Description Brightness level control for the backlight. 00 = daylight (L1). 01 = office (L2). 10 = dark (L3). See the description for the BL_AUTO_ADJ bit. Backlight fade-on/fade-off transfer characteristic. 00 = linear. 01 = square. 10 = Cubic 1. 11 = Cubic 2. Rev. 0 | Page 20 of 28 ADP5501 Bit 3 Name BL_AUTO_AD J R/W R/W 2 OVP_EN R/W 1 FOVR R/W 0 Not used Description 0 = ambient light sensor comparators have no effect on the backlight operating level. The user can manually adjust the backlight operating level using the BL_LVL bits. 1 = ambient light sensor comparators automatically adjust the backlight operating level. The internal state machine takes control of the BL_LVL bits. 0 = soft OVP protection disabled. 1 = soft OVP protection enabled. 0 = backlight fade override is disabled. 1 = backlight fade override is enabled. Table 10. Register 0x03, Backlight Off and Dim Timers (BL_TIME) Bit 7 to 4 Name BL_OFFT R/W R/W 3 to 0 BL_DIMT R/W Description Backlight off timer; the timer should be set before BL_EN is set. 0000 = the timer is disabled. 0001 = 10 sec. 0010 = 15 sec. 0011 = 20 sec. 0100 = 25 sec. 0101 = 30 sec. 0110 = 35 sec. 0111 = 40 sec. 1000 = 50 sec. 1001 = 60 sec. 1010 = 70 sec. 1011 = 80 sec. 1100 = 90 sec. 1101 = 100 sec. 1110 = 110 sec. 1111 = 120 sec. Backlight dim timer; the timer should be set before BL_EN is set. 0000 = the timer is disabled. 0001 = 10 sec. 0010 = 15 sec. 0011 = 20 sec. 0100 = 25 sec. 0101 = 30 sec. 0110 = 35 sec. 0111 = 40 sec. 1000 = 50 sec. 1001 = 60 sec. 1010 = 70 sec. 1011 = 80 sec. 1100 = 90 sec. 1101 = 100 sec. 1110 = 110 sec. 1111 = 120 sec. Rev. 0 | Page 21 of 28 ADP5501 Table 11. Register 0x04, Backlight Fade-In and Fade-Out Timers (BL_FADE) Bit 7 to 4 Name BL_FO R/W R/W 3 to 0 BL_FI R/W Description Backlight fade-out timer; the timer should be set before BL_EN is set. 0000 = the timer is disabled. 0001 = 0.3 sec. 0010 = 0.6 sec. 0011 = 0.9 sec. 0100 = 1.2 sec. 0101 = 1.5 sec. 0110 = 1.8 sec. 0111 = 2.1 sec. 1000 = 2.4 sec. 1001 = 2.7 sec. 1010 = 3.0 sec. 1011 = 3.5 sec. 1100 = 4.0 sec. 1101 = 4.5 sec. 1110 = 5.0 sec. 1111 = 5.5 sec. Backlight fade-in timer; the timer should be set before BL_EN is set. 0000 = the timer is disabled. 0001 = 0.3 sec. 0010 = 0.6 sec. 0011 = 0.9 sec. 0100 = 1.2 sec. 0101 = 1.5 sec. 0110 = 1.8 sec. 0111 = 2.1 sec. 1000 = 2.4 sec. 1001 = 2.7 sec. 1010 = 3.0 sec. 1011 = 3.5 sec. 1100 = 4.0 sec. 1101 = 4.5 sec. 1110 = 5.0 sec. 1111 = 5.5 sec. Table 12. Register 0x05, Level 1 (Daylight) Maximum Current (DAYLIGHT_MAX) Bit 7 6 to 0 Name Not used DAYLIGHT_MAX R/W Description R/W Maximum current setting for the backlight when BL_LVL is at Level 1 (daylight). See Figure 16 for the backlight current vs. sink code relationship. Table 13. Register 0x06, Level 1 (Daylight) Dim Current (DAYLIGHT_DIM) Bit 7 6 to 0 Not used DAYLIGHT_DIM R/W Description R/W Dim current setting for the backlight when BL_LVL is at Level 1 (daylight). See Figure 16 for the backlight current vs. sink code relationship. Table 14. Register 0x07, Level 2 (Office) Maximum Current (OFFICE_MAX) Bit 7 6 to 0 Name Not used OFFICE_MAX R/W Description R/W Maximum current setting for the backlight when BL_LVL is at Level 2 (office). See Figure 16 for the backlight current vs. sink code relationship. Rev. 0 | Page 22 of 28 ADP5501 Table 15. Register 0x08, Level 2 (Office) Dim Current (OFFICE_DIM) Bit 7 6 to 0 Name Not used OFFICE_DIM R/W Description R/W Dim current setting for the backlight when BL_LVL is at Level 2 (office). See Figure 16 for the backlight current vs. sink code relationship. Table 16. Register 0x09, Level 3 (Dark) Maximum Current (DARK_MAX) Bit 7 6 to 0 Name Not used DARK_MAX R/W Description R/W Maximum current setting for the backlight when BL_LVL is at Level 3 (dark). See Figure 16 for the backlight current vs. sink code relationship. Table 17. Register 0x0A, Level 3 (Dark) Dim Current (DARK_DIM) Bit 7 6 to 0 Name Not used DARK_DIM R/W Description R/W Dim current setting for the backlight when BL_LVL is at Level 3 (dark). See Figure 16 for the backlight current vs. sink code relationship. Table 18. Register 0x0B, Backlight Current Value (BL_VALUE) Bit 7 6 to 0 Name Not used BL_VALUE R/W Description R Read-only register that contains the present value to which the backlight is programmed. Table 19. Register 0x0C, Light Sensor Comparator Configuration (ALS_CMPR_CFG) Bit 7 to 5 Name FILT R/W R/W 4 FORCE_RD R/W 3 L3_OUT R 2 L2_OUT R 1 L3_EN R/W 0 L2_EN R/W Description Light sensor filter time. 000 = 0.08 sec. 001 = 0.16 sec. 010 = 0.32 sec. 011 = 0.64 sec. 100 = 1.28 sec. 101 = 2.56 sec. 110 = 5.12 sec. 111 = 10.24 sec. Forces the light sensor comparator to perform a single conversion. This bit is cleared by the internal state machine once the conversion is complete. 0 = ambient light is greater than Level 3 (dark). 1 = the light sensor comparator has detected a change in ambient light from Level 2 (office) to Level 3 (dark). 0 = ambient light is greater than Level 2 (office). 1 = the light sensor comparator has detected a change in ambient light from Level 1 (daylight) to Level 2 (office). 0 = disable Comparator L3_CMPR . 1 = enable Comparator L3_CMPR. If automatic backlight adjustment is required, BL_AUTO_ADJ must be set also. 0 = disable Comparator L2_CMPR. 1 = enable Comparator L2_CMPR. If automatic backlight adjustment is required, BL_AUTO_ADJ must be set also. Table 20. Register 0x0D, Level 2 (Office) Comparator Trip Point (L2_TRIP) Bit 6 to 0 Name L2_TRIP R/W R/W Description Sets the trip value for Comparator L2_CMPR. If ambient light levels fall below this trip point, L2_OUT is set. Each code is equal to 4 μA (typical). Full scale is 1000 μA (typical). Rev. 0 | Page 23 of 28 ADP5501 Table 21. Register 0x0E, Level 2 (Office) Comparator Hysteresis (L2_HYS) Bit 6 to 0 Name L2_HYS R/W R/W Description Sets the hysteresis value for Comparator L2_CMPR. If ambient light levels increase above L2_TRIP + L2_HYS, L2_OUT is cleared. Each code is equal to 4 μA (typical). Full scale is 1000 μA (typical). Table 22. Register 0x0F, Level 3 (Dark) Comparator Trip Point (L3_TRIP) Bit 6 to 0 Name L3_TRIP R/W R/W Description Sets the trip value for Comparator L3_CMPR. If ambient light levels fall below this trip point, L3_OUT is set. Each code is equal to 0.5 μA (typical). Full scale is 127 μA (typical). Table 23. Register 0x10, Level 3 (Dark) Comparator Hysteresis (L3_HYS) Bit 6 to 0 Name L3_HYS R/W R/W Description Sets the hysteresis value for Comparator L3_CMPR. If ambient light levels increase above L3_TRIP + L3_HYS, L3_OUT is cleared. Each code is equal to 0.5 μA (typical). Full scale is 127 μA (typical). Table 24. Register 0x11, LED Control (LED_SINK_CONTROL) Bit 7 to 4 3 Name Not used LED_LAW R/W Description R/W 2 LED2_EN R/W 1 LED1_EN R/W 0 LED0_EN R/W LED current sink fade-on/fade-off transfer characteristic. 0 = linear. 1 = square. 0 = LED2 sink is disabled. 1 = LED2 sink is enabled. 0 = LED1 sink is disabled. 1 = LED1 sink is enabled. 0 = LED0 sink is disabled. 1 = LED0 sink is enabled. Table 25. Register 0x12, LED On and Off Timers (LED_TIME) Bit 7 to 6 Name LED_ONT R/W R/W 5 to 4 LED2_OFFT R/W 3 to 2 LED1_OFFT R/W 1 to 0 LED0_OFFT R/W Description Sets the LED on time when used in conjunction with the LEDx_OFFT timer to perform LED blinking. All three LED sinks share this common timer. 00 = 0.2 sec. 01 = 0.6 sec. 10 = 0.8 sec. 11 = 1.2 sec. Sets the LED2 off time when used in conjunction with the LED_ONT timer to perform LED blinking. LED2 stays on continuously if the timer is disabled. 00 = LED2 timer is disabled. 01 = 0.6 sec. 10 = 0.8 sec. 11 = 1.2 sec. Sets the LED1 off time when used in conjunction with the LED_ONT timer to perform LED blinking. LED1 stays on continuously if the timer is disabled. 00 = LED1 timer is disabled. 01 = 0.6 sec. 10 = 0.8 sec. 11 = 1.2 sec. Sets the LED0 off time when used in conjunction with the LED _ONT timer to perform LED blinking. LED0 stays on continuously if the timer is disabled. 00 = LED0 timer is disabled. 01 = 0.6 sec. 10 = 0.8 sec. 11 = 1.2 sec. Rev. 0 | Page 24 of 28 ADP5501 Table 26. Register 0x13, LED Fade-In and Fade-Out Timers (LED_FADE) Bit 7 to 4 Name LED_FO R/W R/W 3 to 0 LED _FI R/W Description LED fade-out timer; the timer should be set before LEDx_EN is enabled. 0000 = the timer is disabled. 0001 = 0.3 sec. 0010 = 0.6 sec. 0011 = 0.9 sec. 0100 = 1.2 sec. 0101 = 1.5 sec. 0110 = 1.8 sec. 0111 = 2.1 sec. 1000 = 2.4 sec. 1001 = 2.7 sec. 1010 = 3.0 sec. 1011 = 3.5 sec. 1100 = 4.0 sec. 1101 = 4.5 sec. 1110 = 5.0 sec. 1111 = 5.5 sec. LED fade-in timer; the timer should be set before LEDx_EN is enabled. 0000 = the timer is disabled. 0001 = 0.3 sec. 0010 = 0.6 sec. 0011 = 0.9 sec. 0100 = 1.2 sec. 0101 = 1.5 sec. 0110 = 1.8 sec. 0111 = 2.1 sec. 1000 = 2.4 sec. 1001 = 2.7 sec. 1010 = 3.0 sec. 1011 = 3.5 sec. 1100 = 4.0 sec. 1101 = 4.5 sec. 1110 = 5.0 sec. 1111 = 5.5 sec. Table 27. Register 0x14, LED0 Sink Current (LED0_CURRENT) Bit 7 to 6 5 to 0 Name Not used LED0_CURRENT R/W Description R/W Sink current setting for LED0. See Figure 33 for LED sink current vs. code relationship. Table 28. Register 0x15, LED1 Sink Current (LED1_CURRENT) Bit 7 to 6 5 to 0 Name Not used LED1_CURRENT R/W Description R/W Sink current setting for LED1. See Figure 33 for LED sink current vs. code relationship. Table 29. Register 0x16, LED2 Sink Current (LED2_CURRENT) Bit 7 to 6 5 to 0 Name Not used LED2_CURRENT R/W Description R/W Sink current setting for LED2. See Figure 33 for the LED sink current vs. code relationship. Rev. 0 | Page 25 of 28 ADP5501 APPLICATIONS INFORMATION VBAT The ADP5501 backlight driver uses a dc-to-dc step-up (boost) converter to achieve the high voltage levels required to drive up to six white LEDs in series. Figure 43 shows the basic asynchronous boost converter topology. VIN 1µF 4.7µH 1µF 2 SW 22 BST 27V I-LIMIT VOUT AUTO LOAD OVP PGND 07780-043 VBAT 1 BOOST CONTROL BL_SNK FB 23 0.65V BACKLIGHT CURRENT CONTROL THERMAL S/D 21 Figure 44. Boost Configuration Figure 43. Basic Asynchronous Boost Converter Topology Assuming an initial steady state condition where the switch has been open for a long time, the output voltage (VOUT) is equal to the input voltage (VIN), minus a diode drop. If the switch is closed, the output voltage maintains its value as the diode blocks its path to ground. The inductor, however, has a voltage differential across its terminals. Current in an inductor cannot change instantaneously, so it increases linearly at a rate of di/dt = VIN/L where L is the inductance value in henrys. If the switch is kept closed, the current increases until the inductor reaches its saturation limit, at which point the inductor becomes a dc path to ground. Therefore, the switch should be kept closed only long enough to build some transient energy in the inductor but not so long that the inductor becomes saturated. When the switch is opened, the current that has built up in the inductor continues to flow (because the current in an inductor cannot change instantaneously), so the voltage at the top of the switch increases and forward biases the diode, allowing the inductor current to charge the capacitor and, therefore, increase the overall output voltage level. If the switch is opened and closed continuously, the output voltage continues to increase. Figure 44 shows the boost configuration used in the ADP5501. A Schottky diode is used due to its fast turn-on time and low forward voltage drop. An input capacitor is added to reduce ripple voltage that is generated on the input supply due to charging/ discharging of the inductor. An integrated power switch is used to control current levels in the inductor. A control loop consisting of a feedback signal, some safety limiting features, and a switch drive signal complete the boost converter topology. The ADP5501 uses a current-limiting, pulse frequency modulation (PFM) control scheme. For medium to large output currents, the converter operates in pseudo continuous conduction mode (CCM). It generates bursts of peak current limited pulses (600 mA typical) in the inductor, as shown in Figure 9. For light output currents, the converter operates in pseudo discontinuous conduction mode (DCM). It generates bursts of small (200 mA, typical) and medium (400 mA, typical) current pulses in the inductor, as shown in Figure 11. To maintain reasonable burst frequencies during very light load conditions, an automatic dummy load feature is available. When enabled, the 1 mA dummy load is activated if the backlight sink current code drops below 8 while in linear law mode or if the backlight sink current code drops below 32 while in square law mode. Safety Features The ADP5501 uses an overvoltage protection (OVP) circuit that monitors the boosted voltage on the output capacitor. If the LED string becomes open (due to a broken LED), the control circuit continually commands the boost voltage to increase. If the boost level exceeds the maximum process rating for the ADP5501, damage to the device can occur. The ADP5501 boost converter has an OVP limit of 27 V (typical). The ADP5501 also has a feature that ramps down the backlight code when an OVP condition is detected. This may be useful in conditions where LEDs with marginally high forward voltages are used in low ambient conditions. The feature can be enabled by setting the OVP_EN bit in Register 0x02. The ADP5501 also features a thermal shutdown circuit. When the die junction temperature reaches 150°C (typical), the boost converter shuts down. It remains shut down until the die temperature falls by 10°C (typical). Rev. 0 | Page 26 of 28 07780-044 CONVERTER TOPOLOGY ADP5501 Component Selection PCB LAYOUT The ADP5501 boost converter is designed for use with a 4.7 μH inductor. Choose an inductor with a sufficient current rating to prevent it from going into saturation. The peak current limit of the ADP5501 is 750 mA (maximum), so choose an inductor with a greater saturation rating. To maximize efficiency, choose an inductor with a low series resistance (DCR). Good PCB layout is important to maximize efficiency and to minimize noise and electromagnetic interference (EMI). To minimize large current loops, place the input capacitor, inductor, Schottky diode, and output capacitor as close as possible to each other and to the ADP5501 using wide tracks (use shapes where possible). The ADP5501 is an asynchronous boost and, as such, requires an external Schottky diode to conduct the inductor current to the output capacitor and LED string when the power switch is off. Ensure that the Schottky diode peak current rating is greater than the maximum inductor current. Choose a Schottky diode with an average current rating that is significantly larger than the maximum LED current. To prevent thermal runaway, derate the Schottky diode to ensure reliable operation at high junction temperatures. To maximize efficiency, select a Schottky diode with a low forward voltage. When the power switch is on, the Schottky diode blocks the dc path from the output capacitor to ground. Therefore, choose a Schottky diode with a reverse breakdown greater than the maximum boost voltage. A 40 V, 1 A Schottky diode is recommended. For thermal relief, the exposed pad of the LFCSP package should be connected to ground (GND). PGND and GND should be connected to each other at the bottom of the output capacitor. Figure 46 shows an example PCB layout with the main power components required for backlight driving EXAMPLE CIRCUIT 1µF 2.7V TO 5.5V 4.7µH 1 PGND 2.2kΩ 10kΩ 2.2kΩ 10kΩ 22 23 BST BL_SNK CAP_OUT 20 21 VBAT 3.3V The input capacitor carries the input ripple current, allowing the input power source to supply only the dc current. Use an input capacitor with sufficient ripple current rating to handle the inductor ripple. A 1 μF X5R/X7R ceramic capacitor rated for 16 V dc bias is recommended for the input capacitance. 2 SW 1µF 16 VDDIO GND 19 GND 24 4 SDA 100nF 3 INT CMP_IN 17 RGB 15 RST NC NC NC NC NC NC The output capacitor maintains the output voltage when the Schottky diode is not conducting. Due to the high levels of boost voltage required, a 1 μF X5R/X7R ceramic capacitor rated for 50 V dc bias is recommended for output capacitance. 6 7 8 9 10 11 LED1 LED2 LED0 12 13 14 3.3V 3.3V Figure 45. Typical Configuration Circuit Note that dc bias characterization data is available from capacitor manufacturers and should be taken into account when selecting input and output capacitors. GND VBAT TOP OF LED STRING VDDIO RST LED0 LED2 CAP_OUT BST Figure 46. Example PCB Layout Rev. 0 | Page 27 of 28 07780-045 NC NC GND CMP_IN NC SCL NC CONNECT EXPOSED PAD TO GND NC ADP5501 SDA NC INT GND LED1 SW VBAT GND PGND BL_SNK BOTTOM OF LED STRING SOLUTION SIZE APPROXIMATELY 47mm2 GND 18 ADP5501 5 SCL 07780-046 1µF ADP5501 OUTLINE DIMENSIONS 0.60 MAX 4.00 BSC SQ TOP VIEW 0.50 BSC 3.75 BSC SQ 0.50 0.40 0.30 1.00 0.85 0.80 12° MAX 0.80 MAX 0.65 TYP SEATING PLANE 19 18 *2.45 EXPOSED PAD 2.30 SQ 2.15 (BOTTOMVIEW) 13 12 7 6 0.23 MIN 2.50 REF 0.05 MAX 0.02 NOM 0.30 0.23 0.18 PIN 1 INDICATOR 24 1 0.20 REF COPLANARITY 0.08 FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. *COMPLIANT TO JEDEC STANDARDS MO-220-VGGD-2 EXCEPT FOR EXPOSED PAD DIMENSION 080808-A PIN 1 INDICATOR 0.60 MAX Figure 47. 24-Lead Lead Frame Chip Scale Package [LFCSP_VQ] 4 mm × 4 mm Body, Very Thin Quad (CP-24-2) Dimensions shown in millilmeters ORDERING GUIDE Model ADP5501ACPZ-RL1 1 Temperature Range −40°C to +85°C Package Description 24-Lead Lead Frame Chip Scale Package [LFCSP_VQ] Z = RoHS Compliant Part. ©2008 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D07780-0-10/08(0) Rev. 0 | Page 28 of 28 Package Option CP-24-2