AAT2860-2

PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Features • Input Voltage Range: 2.7V to 5.5V • I2C Compatible Serial Interface • Tri-Mode Charge Pump ▪ Drives up to Seven LEDs (Backlight/Flash) • Programmable Backlight Current Settings ▪ 32 Levels - 0.5mA to 31mA • Programmable Flash Current ▪ 16 Levels – OFF to 300mA • 1MHz Switching Frequency • Automatic Soft-Start • Three Low Dropout Regulators ▪ 300mA Output Current ▪ 150mV Dropout ▪ Programmable Output from 1.5V to 3.0V ▪ Output Auto-Discharge for Fast Shutdown • Built-In Thermal Protection • -40°C to +85°C Temperature Range • TQFN34-24 Package General Description The AAT2860-x is a highly integrated charge pump-based lighting management unit (LMU) with three low dropout (LDO) regulators optimized for single-cell lithium-ion/ polymer systems. The charge pump provides power for all LED outputs; multiple backlight and flash LED configurations are available. The backlight LED outputs can be programmed up to 31mA each and the flash LED outputs can be programmed up to 300mA each. An I2C compatible serial digital interface is used to enable, disable, and set the current to one of 32 levels for the backlight and one of 16 levels for the flash. A programmable safety timer and flash control input is included for easy flash control. Backlight current matching is better than 3% for uniform display brightness, and flash current matching is better than 5% for uniform power dissipation. The AAT2860-x offers three high-performance low-noise MicroPower™ LDO linear regulators. The regulators are enabled and their output voltages are set through the I2C compatible serial interface. Each LDO can supply up to 300mA load current and ground-pin current is only 80µA making the AAT2860-x ideal for battery-operated applications. The AAT2860-x is available in a Pb-free, space saving TQFN34-24 package and operates over the -40°C to +85°C ambient temperature range. Applications • Camera Enabled Mobile Devices • Digital Still Cameras • Multimedia Mobile Phones Typical Application C1 1µF C2 1µF C1+ C1- C2+ IN VBAT 3.6V CIN 4.7µF IN CIN 4.7µF LED Select Flash Level Select I C Serial Interface 2 C2OUT WLEDs OSRAM LW M673 or equivalent VOUT COUT 2.2µF Flash LEDs Lumiled LXCL-PWF1 or equivalent AAT2860-x BL1 BL2 BL3 BL4 BL5 BL6/FL1 BL7/FL2 LDOA LDOB LDOC AGND PGND LED_SEL FL_LVL SDA SCL LDO_SEL SDA SCL VLDOA at 300mA VLDOB at 300mA VLDOC at 300mA CLDOC 2.2µF CLDOB 2.2µF CLDOA 2.2µF LDO Select 2860.2008.05.1.0 www.analogictech.com 1 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Pin Descriptions Pin # 1 2 3 4 5 Symbol OUT C2+ SDA SCL LED_SEL Description Charge pump output. OUT is the output of the charge pump and supplies current to the backlight and flash LEDs. Connect the backlight and flash LED anodes to OUT. Bypass OUT to PGND with a 2.2μF or larger ceramic capacitor as close to the AAT2860-x as possible. Positive terminal of charge pump capacitor 2. Connect the 1μF charge pump capacitor 2 from C2+ to C2-. I2C compatible serial data input. SDA is the data input of the I2C serial interface. Drive SDA with the I2C data. I2C compatible serial clock input. SCL is the clock input of the I2C serial interface. Drive SCL with the I2C clock. LED Programming Enable Input. When LED_SEL is strobed low-to-high, the backlight and flash LED registers can be programmed via the I2C compatible serial interface. When LED_SEL is strobed high-to-low, all backlight and flash LED outputs are turned off and the backlight and flash LED registers are reset to their default (poweron-reset or POR) values. AAT2860-2/3/4: Flash/Torch enable input. When LED_SEL is strobed high and FL_LVL is strobed high, the flash LED current outputs are enabled and set according to the contents of the flash LED current register. When FL_LVL is strobed high-to-low, the flash LED outputs return to their low-level programmed values. AAT2860-1/5: Connect to AGND. Programming enable input for LDO[A, B, C]. When LDO_SEL is strobed low-to-high, the LDO output voltages can be programmed via the I2C compatible serial interface. Strobing LDO_SEL high-to-low resets the contents of the LDO output voltage registers to their default (POR) values and forces all outputs to 0 (zero) volt. Analog ground. Connect AGND to PGND at a single point as close to the AAT2860-x as possible. LDOC regulated voltage output. LDOC is the voltage output of LDOC. Bypass LDOC to AGND with a 2.2μF or larger ceramic capacitor as close to the AAT2860-x as possible. LDOB regulated voltage output. LDOB is the voltage output of LDOB. Bypass LDOB to AGND with a 2.2μF or larger ceramic capacitor as close to the AAT2860-x as possible. Input power pin for all three LDOs. Connect Pin 11 to Pin 23 with as short a PCB trace as practical. Bypassing this pin with a separate 4.7µF or larger ceramic capacitor will improve performance. LDOA regulated voltage output. LDOA is the voltage output of LDOA. Bypass LDOA to AGND with a 2.2μF or larger ceramic capacitor as close to the AAT2860-x as possible. Backlight LED 1 current sink/channel. BL1 controls the current through backlight LED 1. Connect the cathode of backlight LED 1 to BL1. If not used, connect BL1 to OUT. Backlight LED 2 current sink/channel. BL2 controls the current through backlight LED 2. Connect the cathode of backlight LED 2 to BL2. If not used, connect BL2 to OUT. Backlight LED 3 current sink/channel. BL3 controls the current through backlight LED 3. Connect the cathode of backlight LED 3 to BL3. If not used, connect BL3 to OUT. Backlight LED 4 current sink/channel. BL4 controls the current through backlight LED 4. Connect the cathode of backlight LED 4 to BL4. If not used, connect BL4 to OUT. Backlight LED 5 current sink/channel. BL5 controls the current through backlight LED 5. Connect the cathode of backlight LED 5 to BL5. If not used, connect BL5 to OUT. AAT2860-1/2/3/5/6: Backlight LED 6 current sink/channel. BL6 controls the current through backlight LED 6. Connect the cathode of backlight LED 6 to BL6. If not used, connect BL6 to OUT. AAT2860-4: Flash LED 1 current sink. FL1 controls the current through Flash LED 1. Connect the cathode of Flash LED 1 to FL1. If not used, connect FL1 to OUT. AAT2860-1/5/6: Backlight LED 7 current sink/channel. BL7 controls the current through backlight LED 7. Connect the cathode of backlight LED 7 to BL7. If not used, connect BL7 to OUT. AAT2860-2/3/4: Flash LED or Flash LED 2 current sink. FL2 controls the current through Flash LED 2. Connect the cathode of Flash LED 2 to FL2. If not used, connect FL2 to OUT. Power ground. Connect PGND to AGND at a single point as close to the AAT2860-x as possible. Negative terminal of charge pump capacitor 2. Negative terminal of charge pump capacitor 1. Power input. Connect IN to the input source voltage. Bypass IN to PGND with a 4.7μF or larger ceramic capacitor as close to the AAT2860-x as possible. Positive terminal of charge pump capacitor 1. Connect the 1μF charge pump capacitor 1 from C1+ to C1-. Exposed paddle (bottom) Connect to PGND/AGND as close to the AAT2860-x as possible. 6 FL_LVL (AGND) 7 8 9 10 11 12 13 14 15 16 17 LDO_SEL AGND LDOC LDOB IN LDOA BL1 BL2 BL3 BL4 BL5 BL6 (FL1) 18 19 20 21 22 23 24 EP BL7 (FL2) PGND C2C1IN C1+ 2 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Pin Configuration TQFN34-24 (Top View) PGND C1+ 24 C2C1IN 23 22 21 20 19 18 17 16 15 14 13 OUT C2+ SDA SCL LED_SEL FL_LVL LDO_SEL 1 2 3 4 5 6 7 8 9 10 11 12 BL7/FL2 BL6/FL1 BL5 BL4 BL3 BL2 BL1 AGND IN LDOB LDOC LDOA Part Number Descriptions1 Backlight LED Outputs Part Number AAT2860-1 AAT2860-2 AAT2860-3 AAT2860-4 AAT2860-5 AAT2860-6 Main 7/4 6/4 6/5 5/4 7/6 7/5 Sub 0/3 0/2 0/1 0/1 0/1 0/2 Flash LED Outputs 0 1 1 2 0 0 Absolute Maximum Ratings2 Symbol Description IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6/FL1, BL7/FL2 Voltage to AGND C1+, C2+, SDA, SCL Voltage to AGND LDOA, LDOB, LDOC, LED_SEL, FL_LVL, LDO_LVL, C1-, C2- Voltage to AGND PGND Voltage to AGND Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec) Value -0.3 to 6.0 -0.3 to VOUT + 0.3 -0.3 to VIN + 0.3 -0.3 to 0.3 -40 to 150 300 Units V V V V °C °C TJ TLEAD Thermal Information3, 4 Symbol PD ΘJA Description Maximum Power Dissipation Maximum Thermal Resistance Value 2.0 50 Units W °C/W 1. Backlight and Flash Configuration within a part number is configured though the I2C serial interface. For example, clearing the MEQS flag (set to “0”) in the AAT2860-1’s REG2 register will configure BL1-BL4 LED outputs as MAIN and BL5-BL7 outputs as SUB. 2. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time. 3. Derate 20 mW/°C above 25°C ambient temperature. 4. Mounted on a FR4 circuit board. 2860.2008.05.1.0 www.analogictech.com 3 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Electrical Characteristics1 VIN = 3.6V; CIN = 4.7µF; COUT = CLDO(A, B, C) = 2.2μF; C1 = C2 = 1µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol VIN Description IN Operating Voltage Range Conditions LED_SEL = IN, LDO_SEL = FL_LVL = AGND; ADDR = 02H, DATA = 4CH 2X Mode; LED_SEL = IN, FL_LVL = LDO_ SEL = AGND; BL1-BL7 = OPEN 2X Mode; LED_SEL = IN, FL_LVL = IN; LDO_SEL = AGND; FL1-FL2 = OPEN LED_SEL = FL_LVL = AGND, LDO_SEL = IN; ADDR = 01H; DATA = 0EH; No Load LED_SEL, LDO_SEL, FL_LVL = AGND Min 2.7 Typ Max 5.5 0.65 5.5 5.5 220 1.0 Units V mA mA mA µA µA ˚C ˚C V V MHz µs µs IIN IN Operating Current IIN(SHDN) IN Shutdown Current Over-Temperature Shutdown Threshold TSD TSD(HYS) Over-Temperature Shutdown Hysteresis Charge Pump Section BL1-BL7 Charge Pump Mode Transition VIN(TH_H, BL) Hysteresis FL1-FL2 Charge Pump Mode Transition VIN(TH_H, FL) Hysteresis Charge Pump Oscillator Frequency fOSC tCP(SS) Charge Pump Soft-start Time BL1-BL5, BL6/FL1, BL7/FL2 LED Drivers tLED(SU) IBLx IBL_(DATA7DH) 140 15 LED_SEL = IN, ADDR = 02H, DATA = 6CH; FL_LVL = AGND, LDO_SEL = AGND 0.15 1 TA = 25°C TA = 25°C OUT: 0V to IN LED_SEL = IN, ADDR=02H, DATA=6CH; VIN – VF = 1V; FL_LVL = LDO_SEL = AGND LED_SEL = IN, ADDR=02H, DATA=7DH; VIN – VF = 1V; FL_LVL = LDO_SEL = AGND LED_SEL = IN, ADDR=02H, DATA=6CH; VIN – VF = 1V; FL_LVL = LDO_SEL = AGND LED_SEL = IN, ADDR=02H, DATA=60H, VIN – VF = 1V; FL_LVL = LDO_SEL = AGND LED_SEL = IN, ADDR=02H, DATA=6CH; VIN – VF = 1V; FL_LVL = LDO_SEL = AGND LED_SEL = FL_LVL = IN, ADDR=04H, DATA=03H; VIN - VF = 1V, LDO_SEL = AGND LED_SEL = FL_LVL = IN, ADDR = 04H, DATA=60H; VIN - VF = 1V, LDO_SEL = AGND LED_SEL = FL_LVL = IN, ADDR = 04H, DATA=03H; VIN - VF = 1V, LDO_SEL= AGND LED_SEL = FL_LVL = IN, ADDR = 04H, DATA=60H; VIN - VF = 1V, LDO_SEL = AGND 27 2.55 1 100 20 30 3 3 0.18 1 270 300 330 33 3.45 LED Output Current Start-up Time BL1-BL7 Current Accuracy BL1-BL7 Current Accuracy BL1-BL7 Current Matching2 BL1-BL7 Charge Pump Transition Threshold BL1-BL7 Automatic Fade Out Timer FL1, FL2 Current Accuracy, -4 Option mA mA % V s mA ΔI(BLx)/ IBL(AVG) VBL_(TH) tFADE IFL[1/2] IFL[1/2] FL1, FL2 Current Accuracy, -4 Option 54 60 66 mA IFL2 IFL2 FL2 Current Accuracy, -2 and -3 Options 540 600 660 mA FL2 Current Accuracy, -2 and -3 Options 108 120 132 mA 1. The AAT2860 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. Current matching is defined as the deviation of any sink/channel current from the average of all active channels. 4 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Electrical Characteristics1 VIN = 3.6V; CIN = 4.7µF; COUT = CLDO(A, B, C) = 2.2μF; C1 = C2 = 1µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C. Symbol Description Conditions ILDO = 1mA to 300mA; TA = 25°C ILDO = 1mA to 300mA; TA = -40°C to +85°C Min -1.5 -3 300 Typ Max +1.5 +3 Units % % mA LDO Regulators LDOA, LDOB, LDOC Output ΔVLDO[A/B/C]/ VLDO[A/B/C] Voltage Tolerance LDOA, LDOB, LDOC Maximum ILDO[A/B/C](MAX) Load Current LDOA, LDOB, LDOC Dropout VLDO[A/B/C](DO) Voltage2 ∆VLDO/ Line Regulation VLDO*∆VIN LDOA, LDOB, LDOC Power PSRR[A/B/C] Supply Rejection Ratio LDOA, LDOB, LDOC AutoRLDO_(DCHG) Discharge Resistance I2C Logic and Control Interface SDA, SCL, LED_SEL, FL_LVL, VIL LDO_SEL Input Low Threshold SDA, SCL, LED_SEL, FL_LVL, VIH LDO_SEL Input High Threshold SDA, SCL, LED_SEL, FL_LVL, IIN LDO_SEL Input Leakage Current SCL Clock Frequency fSCL tLOW SCL Clock Low Period tHIGH SCL Clock High Period tHD_STA Hold Time START Condition tSU_STA Setup Time for Repeat START tSU_DAT SDA Data Setup Time tHD_DAT SDA Data HOLD Time tSU_STO Setup Time for STOP Condition Bus Free Time Between STOP tBUF and START Conditions VLDO[A/B/C] ≥ 2.7V; ILDO = 150mA VIN = (VLDO[A/B/C] + 1V) to 5V ILDO[A/B/C] =10mA, 1kHz 75 0.09 40 20 150 mV %/V dB Ω 2.7V ≤ VIN ≤ 5.5V 2.7V ≤ VIN ≤ 5.5V SDA = SCL = LED_SEL = FL_LVL = LDO_SEL = 5V 1.4 -1 0 1.3 0.6 0.6 0.6 500 0.5 0.6 1.3 0.4 V V 1 400 µA kHz µs µs µs µs ns µs µs µs 1. The AAT2860 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2. VDO[A/B/C] is defined as VIN – LDO[A/B/C] when LDO[A/B/C] is 98% of nominal. 2860.2008.05.1.0 www.analogictech.com 5 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit I2C Compatible Interface Timing Details t t t t t t t t t 6 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Typical Characteristics Backlight Mode Efficiency vs. Input Voltage 100 90 100 90 Flash Efficiency vs. Input Voltage 160mA/ch, VF = 3.15V 320mA/ch, VF = 3.25V Efficiency (%) 80 70 60 50 40 30 2.7 Efficiency (%) 30mA/ch, VF = 3.95V 15mA/ch, VF = 3.5V 4.2mA/ch, VF = 3.4V 3.1 3.5 3.9 4.3 4.7 5.1 5.5 80 70 60 50 40 30 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Input Voltage (V) Input Voltage (V) Backlight Current Matching vs. Temperature (VIN = 3.6V; 30mA/Channel) Backlight Output Current (mA) 33 32 Charge Pump Output Turn-On Characteristic (VIN = 3.6V; 0mA/Channel; COUT = 2.2V) 4 Charge Pump VOUT (bottom) (V) VLED_SEL (top) (V) 31 30 29 28 27 26 25 -40 2 0 4 3 2 1 0 Channel 1 - Channel 5/6/7 -15 10 35 60 85 Temperature (°C) Time (20µs/div) Flash Mode Turn-On Characteristic (VIN = 4.2V; 300mA/Channel; 1x Mode) 4 Flash Mode Turn-On Characteristic (VIN = 3.6V; 300mA/Channel; 1.5x Mode) 4 VFL_LVL (2V/div) VOUT (2V/div) VFLX (2V/div) IIN (200mA/div) Time (20µs/div) 4 2 0 2 0 VFL_LVL (2V/div) VOUT (2V/div) 4 2 0 2 0 600 400 200 0 VFLX (2V/div) IIN (200mA/div) 600 400 200 0 Time (50µs/div) 2860.2008.05.1.0 www.analogictech.com 7 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Typical Characteristics Flash Mode Turn-On Characteristic (VIN = 2.8V; 300mA/Channel; 2x Mode) VFL_LVL (2V/div) VOUT (2V/div) VFLX (2V/div) IIN (200mA/div) Time (50µs/div) 4 2 0 600 400 200 0 4 2 0 Backlight Mode Turn-On Characteristic (VIN = 4.6V; 30mA/Channel; 1x Mode) 4 VSDA (2V/div) VOUT (2V/div) VBLX (2V/div) IIN (100mA/div) Time (100µs/div) 4 2 0 2 0 200 100 0 Backlight Mode Turn-On Characteristic (VIN = 3.6V; 30mA/Channel; 1.5x Mode) 4 Backlight Mode Turn-On Characteristic (VIN = 3.2V; 30mA/Channel; 2x Mode) 4 VSDA (2V/div) VOUT (2V/div) VBLX (2V/div) IIN (200mA/div) Time (100µs/div) 4 2 0 2 0 VSDA (2V/div) VOUT (2V/div) VBLX (2V/div) 4 2 0 2 0 400 200 0 400 IIN (200mA/div) Time (100µs/div) 200 0 Backlight Mode Turn-Off Characteristic (VIN = 3.6V; 30mA/Channel; 1.5x Mode) 4 Operating Characteristic (30mA/Channel Backlight; 1.5x Mode; VIN = 3.6V; COUT = 2.2µF) Charge Pump VOUT (AC coupled) (bottom) (mV) VIN (AC coupled) (top) (mV) 20 10 0 100 50 0 -50 VSDA (2V/div) VDIODE (2V/div) 2 0 4 2 0 2 IIN (2mA/div) 0 Time (200µs/div) Time (500ns/div) 8 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Typical Characteristics Operating Characteristic LDO Output Voltage Deviation (%) (30mA/Channel Backlight; 2x Mode; VIN = 3.2V; COUT = 2.2µF) Charge Pump VOUT (AC coupled) (bottom) (mV) VIN (AC coupled) (top) (mV) 20 10 0 20 10 0 -10 -20 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 0.1 1 10 100 1000 LDOs A/B/C Load Regulation (VIN = 3.6V) VLDO = 3.0V VLDO = 1.5V Time (500ns/div) Load Current (mA) LDO Output Voltage vs Temperature LDO Output Voltage Deviation (%) LDO Output Voltage Deviation (%) (VIN = 3.6V; ILDO = 0mA) 1.5 1 0.5 0 -0.5 -1 -1.5 -40 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 2.7 LDOs A/B/C Line Regulation (ILDO = 10mA) VLDO = 3.0V VLDO = 1.5V VLDO = 3.0V VLDO = 1.5V -15 10 35 60 85 3.1 3.5 3.9 4.3 4.7 5.1 5.5 Temperature (°C) Input Voltage (V) LDOs A/B/C Load Transient Response (ILDO = 10mA to 200mA; VIN = 3.6V; VLDO = 1.8V; CLDO = 2.2µF) 200 LDOs A/B/C Line Transient Response (VIN = 3.6V to 4.2V; ILDO = 10mA; VLDO = 1.8V; CLDO = 2.2µF) 4.4 VLDO (bottom) (V) VLDO (bottom) (V) ILDO (top) (mA) 100 0 2.00 1.90 1.80 1.70 1.60 4.0 VIN (top) (V) 3.6 1.82 1.81 1.80 1.79 1.78 Time (20µs/div) Time (1ms/div) 2860.2008.05.1.0 www.analogictech.com 9 PRODUCT DATASHEET AAT2860 AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Typical Characteristics LDOs A/B/C Turn-On Characteristic (VLDO = 3.0V; VIN = 3.6V; CLDO = 2.2µF) 4 4 LDOs A/B/C Turn-On Characteristic (VLDO = 1.5V; VIN = 3.6V; CLDO = 2.2µF) VLDO (bottom) (V) VLDO (bottom) (V) VSDA (top) (V) VSDA (top) (V) 2 0 4 3 2 1 0 2 0 1.5 1.0 0.5 0.0 Time (20µs/div) Time (20µs/div) 10 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Functional Block Diagram IN IN C1C1+ C2C2+ OUT LDOA 1x/1.5x/2x Tri-mode Charge pump LDOB LDOC REF 7 BL1 SDA SCL LED_SEL FL_LVL LDO_SEL BL7/FL2 AAT2860-x PGND AGND Control Logic BL2 BL3 BL4 BL5 BL6/FL1 Functional Description The AAT2860-x is a highly integrated backlight and photo-flash driver with three LDO regulators. The charge pump LED driver powers the backlight and flash LEDs from the 2.7V to 5.5V input voltage. The LDO regulators get their power from the same input and produce regulated output voltage between 1.5V and 3.0V. Control of the LEDs and the LDO output voltage is through an I2C compatible serial interface for easy programming. or the flash current sink/channel drops below 450mV, the charge pump goes to the next higher mode (from 1x to 1.5x or from 1.5x to 2x mode) to maintain sufficient LED voltage for constant LED current. The AAT2860-x continuously monitors the LED forward voltages and uses the input voltage to determine when to reduce the charge pump mode for better efficiency. There is also a 150mV mode-transition hysteresis that prevents the charge pump from oscillating between modes. LED Drivers The AAT2860-x drives up to seven backlight LEDs up to 31mA each and up to two flash LEDs up to 300mA each. The LEDs are driven from a charge pump to insure that constant current is maintained over the entire battery voltage range. The charge pump automatically switches from 1x, 1.5x, and 2x modes and back to maintain the LED current while minimizing power loss for high efficiency. The charge pump operates at the high 1MHz switching frequency allowing the use of small 1μF ceramic fly capacitors. The charge pump is controlled by the voltage across the LED current sinks. When any one of the active backlight current sink sink/channel voltages drops below 180mV LED Current Control Both the backlight and flash LED currents are controlled through an I2C compatible serial interface. The backlight LED current can be set between 0.5mA and 31mA in 1mA steps while the flash LED current can be set between 0mA and 300mA in 20mA steps. The backlight LED currents match to within 3% while the flash LED currents match to within 5%. To eliminate the latency of the I2C compatible serial interface, the flash LED is enabled through a dedicated input, FL_LVL. The AAT2860-x also include a safety timer that prevents overstress of the flash LED(s). This is important because many flash LEDs operate for a brief period beyond their steady-state operating limitations. If the flash driving hardware and/or software fails to turn 11 2860.2008.05.1.0 www.analogictech.com PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit always be set to “0”. The timing diagram in Figure 1 below shows the typical transmission protocol. the LED off, the safety timer insures that the LED or other circuitry is not damaged. Both the backlight and flash LED currents are programmed through the I2C compatible serial interface as are the backlight fade timer, the flash safety timer, and the torch/ flash inhibit current levels. See the “I2C Compatible Serial Interface” section of this datasheet for more information on setting the LED currents. To enable the flash LED(s), strobe both LED_SEL and FL_LVL inputs low-to-high. As long as FL_LVL signal is held high, the flash LED remains on unless it is on longer than the safety timer period. If this occurs, the flash LED is turned off. I2C Compatible Serial Interface Protocol The I2C compatible serial interface protocol is shown in Figure 1. Devices on the bus can be either master or target devices. Both master and target devices can both send and receive data over the bus, with the difference being that the master device controls all communication on the bus. The AAT2860-x acts as a target device on the bus and is only capable of receiving data and does not transmit data over the bus. The I2C communications begin with the master generating a START condition. Next, the master transmits the 7-bit device address and a read/write bit. Each target device on the bus has a unique address. If the address transmitted by the master matches the device address, the target device transmits an acknowledge (ACK) signal to indicate that it is ready to receive data. Since the AAT2860-x only reads from the master, the read/write bit must be set to “0”. Next, the master transmits an 8-bit register address, and the target device transmits an ACK to indicate that it has received the register address. Next, the master transmits an 8-bit data word, and again the target device transmits an ACK indicating that it has received the data. This process continues until the master is finished writing to the target device at which time the master generates a STOP condition. LDO Regulators The AAT2860-x family include three LDO regulators. These regulators are powered from the battery and produce a fixed output voltage set through the I2C compatible serial interface. The output voltage can be set to one of 16 output voltages between 1.5V and 3.0V. The LDOs can also be turned on/off through the I2C compatible serial interface. The LDO regulators require only a small 2.2μF ceramic output capacitor for stability. If improved load transient response is required, larger-valued capacitors can be used without stability degradation. I2C Compatible Serial Interface The AAT2860-x uses an I2C serial interface to set the LED currents, the flash timer period, the LDO on/off and output voltage, as well as other housekeeping functions. The I2C interface takes input from a master device while the AAT2860-x acts as a target to the master. The I2C protocol uses two open-drain inputs; SDA (serial data line) and SCL (serial clock line). Both inputs require an external pull up resistor, typically to the input voltage. The I2C protocol is bidirectional and allows target devices and masters to both read and write to the bus. AAT2860 only supports the write protocol and therefore the Read/Write bit must START and STOP Conditions START and STOP conditions are always generated by the master. Prior to initiating a START, both the SDA and SCL pin are active. As shown in Figure 2, a START condition is when the master pulls the SDA line low and, after the START condition hold time (tHD_STA), the master strobes the SCL line low. A START condition acts as a signal to devices on the bus that the device producing the START condition is active and will be communicating on the bus. SCL SDA Start AAT 2860 Device Address 0x60 W ACK Address = 02h ACK Data = 40h ACK Stop Figure 1: Typical I2C Timing Diagram. 12 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit signifies the power on reset (POR) value of a register, the superscript "2" signifies the default value of "1" for a particular bit of a register, and the superscript "3" signifies "Don't Care" or "Reserved." A STOP condition, as shown in Figure 2, is when SCL changes from low to high followed after the STOP condition setup time (tSU_STO), by the SDA low-to-high transition. The master does not issue an ACK and releases both the SCL and SDA line. Transferring Data Addresses and data are sent with the most significant bit transmitted first and the least significant bit transmitted last. After each address or data transmission, the target device transmits an ACK signal to indicate that it has received the transmission. The ACK signal is generated by the target after the master releases the SDA data line by driving the SDA data line low. LDO Control Registers, REG0 and REG1 Configuring and controlling the AAT2860-x’s three LDO regulators is performed by applying a low-to-high strobe on the LDO_SEL pin and then programming registers REG0 and REG1 over the I2C compatible interface. Two 4-bit nibbles in REG0 set the output voltages for LDOA and LDOB to one of 16 levels. In REG1, the most-significant nibble programs LDOC’s output voltage while the least-significant 4-bit nibble controls each LDO’s ON/OFF status. Upon power-on reset (POR), all three LDO outputs are held to 0V or AGND. The programmed LDO output voltage will only appear after writing a “1” to each or all REG1[D3:D1] locations. If a high-to-low transition is applied to the LDO_SEL pin, all three LDO outputs are forced to 0V and the register contents are reset to their POR values. The available LDO output voltages are shown in Table 2. I2C Serial Programming Registers The AAT2860’s I2C programming registers are listed in Table 1. There are six registers, two for backlight LED configuration/control, one for flash/lamp LED configuration/control, and two registers to control the three LDOs. For the remainder of this document the superscript "1" D7 REG0 REG1 REG2 REG3 REG4 REG5 LDOA[3] LDOC[3] X3 FLOOR[1] F_HI[3] X3 2 D6 LDOA[2] LDOC[2] MEQS2 FLOOR[0] F_HI[2] X3 2 D5 LDOA[1] LDOC[1] MAIN_ON SUB_ON F_HI[1] X3 D4 LODA[0] LODC[0] WM[4] WS[4] F_HI[0] X3 D3 LDOB[3] ENLDO_C WM[3] WS[3] F_TIME[1] X3 D2 LDOB[2] ENLDO_B WM[2] WS[2] F_TIME[0] X3 D1 LDOB[1] ENLDO_A WM[1] WS[1] F_LO[1] 2 D0 LODB[0] X3 WM[0] WS[0] F_LO[0]2 NOFADE_S2 NOFADE_M2 Table 1: AAT2860-x Configuration/Control Register Allocation. LDOx[4:0] 00001 0001 0010 0011 0100 0101 0110 0111 LDO VOUT [A/B/C] (V) 1.51 1.6 1.7 1.8 1.9 2.0 2.1 2.2 LDOx[4:0] 1000 1001 1010 1011 1100 1101 1110 1111 LDO VOUT [A/B/C] (V) 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 Table 2: LDO[A:C] Output Voltage Control Data 1. Denotes the default (power-on-reset) value. 2. Denotes default value is "1" or ON. 3. Don't Care or Reserved. 2860.2008.05.1.0 www.analogictech.com 13 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit t t Figure 2: I2C STOP and START Conditions. START: A High “1” to Low “0” Transition on the SDA Line While SCL is High “1” STOP: A Low “0” to High “1” Transition on the SDA Line While SCL is High “1” Figure 3: I2C Address Bit; 7-bit Slave Address (A6-A0), 1-bit Read/Write (R/W), 1-bit Acknowledge (ACK). Figure 4: I2C Register Address and Data Bit Map; 8-bit Data (D7-D0), 1-bit Acknowledge (ACK). 14 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit Based on the programmed LED current level set by WM[4:0] (REG2[D4:D0]) and/or WS[4:0] (REG3[D4:D0]), the AAT2860-x increases/decreases linearly from/to the programmed FLOOR (REG3[D7:D6]) level to/from the current level set for the MAIN (REG2[D4:D0]) and SUB (REG3[D4:D0]) groups during LED ON/OFF transitions. The AAT2860-x’s internal fade response time is approximately 1 second. In addition, the AAT2860-x provides four settings selectable over the I2C interface for the fade function’s LED current floor and these settings are illustrated in Table 5. BL1-BL7 Backlight Control Registers, REG2, REG3, and REG5 The AAT2860-x’s I2C registers REG2 and REG3 control the backlight LED configuration and output current level in each group of outputs. REG2[D6] (MEQS) defines whether all seven LED outputs are controlled as a single group (MEQS = 1 = POR default setting) or are divided into two sets (by writing a “0” into REG2[D6]) for MAIN/ SUB display applications according to the "Part Number Descriptions" table. The default condition for all backlight outputs (BL1-BL5/ BL6/BL7) is OFF after power-up. If the BL1-BL5/BL6/BL7 outputs are grouped together, REG2 Data Bit 5 (MAIN_ ON) is the ON/OFF control for the group; in this case, REG3[D5] (SUB_ON register bit) is ignored. In the case of the AAT2860-1, setting MEQS = 0 after POR groups the BL1-BL4 outputs together as MAIN and groups the BL5-BL7 outputs as SUB. In this case, REG2[D5] is the ON/OFF control for the MAIN group and REG3[D5] is the ON/OFF control for the SUB group. The AAT2860-x LMU also provides an internal LED current fade function. Fade functionality simply allows for the turning on/off of the LEDs in a smooth controlled transition. The AAT2860 does not have to be manually programmed to avoid the abrupt changes in lighting when white LED drivers are tuned-on and/or turned-off. The fade-in/fade-out operation occurs only during LED on/off transitions. The fade response time is constant regardless of the LED current level. This feature is useful in those applications where turning ON/OFF the backlight current using a smooth transition versus an abrupt ON-to-OFF transition is preferred. If MEQS = 1(REG2[D6]), then fade will be disabled in all LED’s when NO_FADE_M(REG5[D1]) is written to 1. In this case, the contents of NO_ FADE_S(REG5[D0]) are ignored. If MEQS = 0, then fade can be disabled independently for the MAIN and SUB LED groups using the bits NO_FADE_M and NO_FADE_S. FL1-FL2 Flash Driver Control Register REG4 Metal-mask options of the base AAT2860-x design have been configured for backlight and flash/torch applications. As shown in the "Part Number Descriptions" table, there are three combinations for backlight and flash available in this family: the AAT2860-2 (6M+0S+1FL or 4M+2S+1FL), the AAT2860-3 (6M+0S+1FL or 5M+1S+1FL), or the AAT2860-4 (5M+0S+2FL or 4M+1S+2FL). The configuration of the LED outputs is controlled by the MEQS bit. In all cases, the MEQS POR default value of “1” or a userprogrammed value of “0” selects the configuration of the AAT2860-2/3/4 according to Table 6. In all options, the BLX current outputs can be programmed as a single unit (MEQS = 1) or configured in a MAIN/SUB arrangement with separate current levels between MAIN and SUB (MEQS = 0). In the case of the AAT2860-2/3 options where the MEQS bit has been programmed as a “0,” the BL7 LED output is internally re-configured as a single flash/lamp current output, FL. In these options, the maximum available current from the flash output is 600mA (see Table 7) and maximum available current for torch or flash inhibit is 120mA (see Table 9). For the AAT2860-4, the BL6 and the BL7 outputs are internally reconfigured as flash current outputs, FL1 and FL2, respectively, where each flash output is capable of supplying up to 300mA in full-flash mode and up to 60mA in torch mode. 2860.2008.05.1.0 www.analogictech.com 15 PRODUCT DATASHEET AAT2860 ChargePumpTM D7 REG2 REG3 REG5 X3 FLOOR[1] X3 Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit D6 MEQS2 FLOOR[0] X3 D5 MAIN_ON SUB_ON X3 D4 WM[4] WS[4] X3 D3 WM[3] WS[3] X3 D2 WM[2] WS[2] X3 D1 WM[1] WS[1] NOFADE_M2 D0 WM[0] WS[0] NOFADE_S2 Table 3: AAT2860 BL1-BLX Backlight Control Register Allocation. WM[4:0], WS[4:0] 000001 00001 00010 00011 00100 00101 00110 00111 01000 01001 01010 01011 01100 01101 01110 01111 LED Current (mA) 311 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 WM[4:0], WS[4:0] 10000 10001 10010 10011 10100 10101 10110 10111 11000 11001 11010 11011 11100 11101 11110 11111 LED Current (mA) 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0.5 Table 4: MAIN/SUB LED Current - WM/WS[4:0]. For each one of the three options in Table 6, setting/programming the bits in REG4 (see Table 7) sets the fullscale flash current, the torch current levels, and flash safety time duration. The most-significant 4-bit nibble (REG1[D7:D4], or F_HI[3:0]) of the 8-bit data word sets the full-scale flash LED current, the middle two bits (REG4[D3:D2], or F_TIME[1:0]) set the flash safety duration, and the last two bits (REG4[D1:D0], or F_LO[1:0]) are used to set the torch current level. FLOOR[1:0] 001 01 10 11 Fade In/Out Current Level (mA) 0.48 0.97 1.94 2.90 Table 5: Main/Sub LED Current Fade In/Out Level Control. Part Number AAT2860-2 AAT2860-3 AAT2860-4 MEQS Bit (REG2 Data Bit[6]) “1” (Default) 6M+0S+1FL 6M+0S+1FL 5M+0S+2FL “0” 4M+2S+1FL 5M+1S+1FL 4M+1S+2FL Table 6: AAT2860-2/3/4 Flash Driver Control Register Allocation. 1. Denotes default (power-on-reset) value. 2. Denotes default value is "1" or ON. 3. Don't Care or Reserved. 16 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 ChargePumpTM D7 REG4 F_HI[3] 2 Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit D6 F_HI[2] 2 D5 F_HI[1] D4 F_HI[0] D3 F_TIME[1] D2 F_TIME[0] D1 F_LO[1] 2 D0 F_LO[0]2 Table 7: AAT2860-x Flash/Torch Control Register Allocation. Flash Current (mA) per Output F_HI[3:0] 0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 11001 1101 1110 1111 AAT2860-2 or -3 600 560 520 480 440 400 360 320 280 240 200 160 1201 80 40 OFF AAT2860-4 300 280 260 240 220 200 180 160 140 120 100 80 601 40 20 OFF Applications Information LED Selection The AAT2860-x is specifically intended for driving white LEDs. However, the device design will allow the AAT2860-x to drive most types of LEDs with forward voltage specifications ranging from 2.0V to 4.7V. LED applications may include mixed arrangements for display backlighting, color (RGB) LEDs, infrared (IR) diodes and any other load needing a constant current source generated from a varying input voltage. Since the BL1 to BL5/BL6(FL1)/ BL7(FL2) constant current sinks/channels are matched with negligible voltage dependence, the constant current channels will be matched regardless of the specific LED forward voltage (VF) levels. The current sinks/channels in the AAT2860-x maximize performance and make it capable of driving LEDs with high forward voltages. Multiple channels can be combined to obtain a higher LED drive current without complication. Table 8: Flash LED Current Register, F_HI[3:0]. F_TIME[1:0] 00 01 10 11 1 Flash Time (sec) 21 1 0.5 Always ON Device Switching Noise Performance The AAT2860-x operates at a frequency of approximately 1MHz to control noise and limit harmonics that can interfere with the RF operation of cellular telephone handsets or other communication devices. The AAT2860-x soft-start feature prevents noise transient effects associated with in-rush currents during the start up of the charge pump circuit. Table 9: Flash Safety Timer Data, F_TIME[1:0]. Total Output Torch Current (mA) F_LO[1:0] 00 01 10 111 AAT2860-2 or -3 120 80 40 01 AAT2860-4 60 40 20 01 Power Efficiency and Device Evaluation Charge-pump efficiency discussion in the following sections accounts only for the efficiency of the charge pump section itself. Due to the unique circuit architecture and design of the AAT2860-x, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power. Table 10: Torch Data, F_LO[1:0]. 1. Denotes the default (power-on-reset) value. 2. Denotes default value is "1" or ON. 2860.2008.05.1.0 www.analogictech.com 17 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit The expression to define the estimated ideal efficiency (η) for the AAT2860 in 1x mode is as follows: Since the AAT2860-x outputs are pure constant current sinks and typically drive individual loads, it is difficult to measure the output voltage for a given output (BL1 to BL5, BL6/FL1, and BL7/FL2) to derive an overall output power measurement. For any given application, white LED forward voltage levels can differ, yet the output drive current will be maintained as a constant. This makes quantifying output power a difficult task when taken in the context of comparing to other white LED driver circuit topologies. A better way to quantify total device efficiency is to observe the total input power to the device for a given LED current drive level. The best White LED driver for a given application should be based on trade-offs of size, external component count, reliability, operating range and total energy usage...Not just “% efficiency”. The AAT2860-x efficiency may be quantified under very specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads applied to outputs BL1 through BL5, BL6(FL1), and BL7(FL2) for a given constant current setting. Depending on the combination of VIN and voltages sensed at the current sinks/channels, the device will operate in “Load Switch” mode. When any one of the voltages sensed at the current sinks/channels nears dropout the device will operate in 1.5x or 2x charge pump mode. Each of these modes will yield different efficiency values. One should refer to the following two sections for explanations for each operational mode. η= PLEDs VLED1 · ILED1 + ... + VLEDX · ILEDX = PIN VIN · IIN X · VLEDX · ILEDX ; X = 1, 2, 3, ..., 6 or 7 and IIN = X · ILEDX VIN · IIN η= VLEDX η= V IN The AAT2860’s charge pump is a fractional charge pump which will boost the input supply voltage in the event where VIN is less then the required output voltage across the backlight white LED load. The efficiency can be simply defined as a linear voltage regulator with an effective backlight white LED forward voltage that is equal to one and a half (1.5x mode) times the input voltage. With an ideal 1.5x charge pump, the input current is 1.5x of the output current. The expression to define the estimated ideal efficiency (η) for the AAT2860 in 1.5x mode is as follows: η= η= PLEDs VLED1 · ILED1 + ... + VLEDX · ILEDX = PIN VIN · IIN X · VLEDX · ILEDX ; X = 1, 2, 3, ..., 6 or 7 and IIN = 1.5(X · ILEDX) VIN · IIN IN VLEDX η = 1.5V Device Power Efficiency The AAT2860’s charge pump conversion efficiency is defined as the power delivered to the white LED load divided by the input power: The same calculations apply for the AAT2860 in 2x mode where for an ideal 2x charge pump, the input current is 2x of the output current. The expression for the estimated ideal efficiency (η) for the AAT2860 in 2x mode is as follows: η= PLEDs VLED1 · ILED1 + ... + VLEDX · ILEDX = PIN VIN · IIN VLEDx = White LED Forward Voltage (VF) ILEDx = White LED Bias Current (ID) X = Number of White LEDs η= PLEDs VLED1 · ILED1 + VLED2 · ILED2 = PIN VIN · IIN X · VLEDX · ILEDX ; X = 1, 2, 3,..., 6 or 7 and IIN = 2(X · ILEDX) VIN · IIN η= VLEDX η = 2V IN 18 www.analogictech.com 2860.2008.05.1.0 PRODUCT DATASHEET AAT2860 ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit PCB Layout To achieve adequate electrical and thermal performance, careful attention must be given to the PCB layout. In the worst-case operating condition, the chip must dissipate considerable power at full load. Adequate heat-sinking must be achieved to ensure intended operation. Figures 6 and 7 illustrate an example PCB layout. The bottom of the package features an exposed metal pad. The exposed pad acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. The junction-to-ambient thermal resistance (θJA) for the connection can be significantly reduced by following a couple of important PCB design guidelines. The PCB area directly underneath the package should be plated so that the exposed paddle can be mated to the top layer PCB copper during the reflow process. Multiple copper plated thru-holes should be used to electrically and thermally connect the top surface pad area to additional ground plane(s). The chip ground is internally connected to both the exposed pad and to the AGND and PGND pins. It is good practice to connect the GND pins to the exposed pad area with traces. The flying capacitors (C1 and C2), input capacitors (C3 and C4), and output capacitor (C5, C6, C7, and C8) should be connected as close as possible to the IC. In addition to the external passive components being placed as close as possible to the IC, all traces connecting the AAT2860 should be as short and wide as possible to minimize path resistance and potential coupling. Capacitor Selection Careful selection of the eight external capacitors CIN, C1, C2, CLDO(A/B/C), and COUT are important because they will affect turn on time, output ripple and transient performance. Optimum performance will be obtained when low ESR (