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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Features
* Input Voltage Range: 2.7V to 5.5V * AS2Cwire Serial Interface * Tri-Mode Charge Pump Drives up to Eight LEDs (Backlight/Flash) * Programmable Backlight Current Settings 31mA Maximum Current per Channel 32 Linear Current Settings Independent Main/Sub Settings Programmable Fade-In and Fade-Out * Programmable Flash Current 600mA Total Flash Current 16 Linear Current Settings 1- or 2-Channel Configuration * 1MHz Switching Frequency * Automatic Soft-Start * Three Linear Low Dropout Regulators 300mA Output Current 150mV Dropout Programmable Output Voltage from 1.2V to 3.3V Output Auto-Discharge for Fast Shutdown * Built-In Thermal Protection * Automatic Soft Start * -40C to +85C Temperature Range * TQFN34-24 Package
General Description
The AAT2861 is a highly integrated charge pump-based lighting management unit (LMU) offering eight LED channels with three linear 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 output current can be programmed up to 600mA total. AnalogicTech's AS2CwireTM (Advanced Simple Serial ControlTM) single-wire 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 separate flash control input are 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 AAT2861 also offers three high-performance lownoise MicroPowerTM LDO linear regulators. The regulators output voltages are set through the AS2Cwire serial interface. Each LDO can supply up to 300mA load current and ground-pin current is only 80A, making the AAT2861 ideal for battery-operated applications. The AAT2861 is available in a Pb-free, space-saving TQFN34-24 package and operates over the -40C to +85C ambient temperature range.
Applications
* Camera Enabled Mobile Devices * Digital Still Cameras * Multimedia Mobile Phones
Typical Application
CF1 1F C1+ IN VBAT 3.6V CIN 2.2F IN EN/SET FL_EN EN_ LDOA EN_ LDOB/C BL1 BL2 BL3 BL4 FL_EN BL5 BL6 EN_ LDOA BL7/FL2 FL1 EN_LDOB/C EN/SET LDOA LDOB LDOC AGND PGND CF2 1F C2OUT
C1- C2+
WLEDs OSRAM LW M673 or equivalent VOUT COUT 2.2F Flash LEDs Lumiled LXCL-PWF1 or equivalent
AAT2861-x
V LDOC at 300mA C LDOC 2.2F
V LDOB at 300mA C LDOB 2.2F
V LDOA at 300mA C LDOA 2.2F
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Pin Descriptions
Pin #
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Symbol
OUT C2+ EN/SET FL_EN EN_LDOA EN_LDOB/C AGND LDOC IN LDOB LDOA BL1 BL2 BL3 BL4 BL5 BL6
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 2.2F or larger ceramic capacitor as close to the AAT2861 as possible. Positive terminal of charge pump capacitor 2. Connect the 1F charge pump capacitor 2 from C2+ to C2-. AS2Cwire serial input. EN/SET is the address and data input of the AS2Cwire serial interface. AS2Cwire is used to control backlight, flash and LDO functions. Flash enable. FL_EN is the enable control for the Flash LEDs. For the FL_EN pin to enable the flash current, the EN/SET pin must also be pulled high. LDO A enable pin. EN_LDOA turns on or off LDO regulator A. The EN/SET pin must also be pulled high for LDO A to be enabled. The EN_LDOA input can be overwritten via the AS2Cwire interface to disable LDO A. LDO B and LDO C enable pin. EN_LDOB/C enables both LDO regulators B and C. The EN/SET pin must also be pulled high for the LDO regulators to be enabled. The EN_LDOB/C input can be overwritten via the AS2Cwire interface to disable either LDO B or LDO C. Analog ground. Connect AGND to PGND at a single point as close to the AAT2861 as possible. LDOC is the voltage output of LDO C. Bypass LDOC to AGND with a 2.2F or larger capacitor as close to the AAT2861 as possible. Input power pin for all three LDOs. Connect Pin 9 to Pin 23 with as short a PCB trace as practical. LDOB is the voltage output of LDO B. Bypass LDOB to AGND with a 2.2F or greater capacitor as close to the AAT2861 as possible. LDOA is the voltage output of LDO A. Bypass LDOA to AGND with a 2.2F or larger ceramic capacitor as close to the AAT2861 as possible. Backlight LED 1 current sink. 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. 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. 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. 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. BL5 controls the current through backlight LED 5. Connect the cathode of backlight LED 5 to BL5. If not used, connect BL5 to OUT. Backlight LED 6 current sink. BL6 controls the current through backlight LED 6. Connect the cathode of backlight LED 6 to BL6. If not used, connect BL6 to OUT. AAT2861-1/3: Backlight LED 7 current sink. BL7 controls the current through backlight LED 7. Connect the cathode of backlight LED 7 to BL7. If not used, connect BL7 to OUT. AAT2861-2: 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. 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. Power ground. Connect PGND to AGND at a single point as close to the AAT2861 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 2.2F or larger ceramic capacitor as close to the AAT2861 as possible. Positive terminal of charge pump capacitor 1. Connect the 1F charge pump capacitor 1 from C1+ to C1-. Exposed paddle (bottom) Connect to PGND/AGND.
18
BL7 (FL2)
19 20 21 22 23 24 EP
FL1 PGND C2C1IN C1+
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Pin Configuration
TQFN34-24 (Top View)
PGND C2C1IN C1+
24 23 22 21 20 19 18 17 16 15 14 13 8 9 10 11 12
OUT C2+ EN/SET FL_EN EN_LDOA EN_LDOB/C AGND
1 2 3 4 5 6 7
FL1 BL7 (FL2) BL6 BL5 BL4 BL3 BL2
BL1 LDOA LDOB IN LDOC
Part Number Descriptions1
Backlight LED Outputs Part Number
AAT2861IMK-1-T1 AAT2861IMK-2-T1 AAT2861IMK-3-T1 Main 4 4 5 Sub 3 2 2
Flash LED Outputs
1 2 1
Absolute Maximum Ratings2
Symbol Description
IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6, BL7/FL2, FL1 Voltage to AGND C1+, C2+ Voltage to AGND C1-, C2-, LDOA, LDOB, LDOC, EN/SET, FL_EN, EN_LDOA, EN_LDOB/C 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 JA
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 AS2Cwire serial interface. For example, disabling the "Main Equals Sub" feature (Address 8, Data 5 - 8) in the AAT2861-1 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 20mW/C above 25C ambient temperature. 4. Mounted on a FR4 circuit board.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Electrical Characteristics1
VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol
VIN
Description
Conditions
EN/SET = IN, BL1-BL7 = IN, FL_EN = EN_LDOA = EN_LDOB/C = AGND 2X Mode; EN/SET = IN, FL_EN = EN_LDOA = EN_LDOB/C = AGND; BL1-BL7 = OPEN EN/SET = EN_LDOA = EN_LDOB/C = IN; FL_EN = AGND; ADDR = 3; DATA = 1; No Load EN/SET = EN_LDOA = IN; FL_EN = EN_LDOB/C = AGND, ADDR = 3; DATA = 1; No Load EN/SET, FL_EN, EN_LDOA, EN_LDOB/C = AGND
Min
2.7
Typ
Max
5.5 600 5.5 225 80 1.0
Units
V A mA A A A C C V mA V V MHz s
IN Operating Voltage Range IN Operating Current (1x mode, Main Channels enabled, IBLX not included) IN Operating Current (2x mode, Main Channels enabled, IBLX not included) IIN IN Operating Current (LDOA, LDOB and LDOC enabled) IN Operating Current (Only LDOA enabled) IN Shutdown Current IIN(SHDN) Over-Temperature Shutdown Threshold TSD Over-Temperature Shutdown Hysteresis TSD(HYS) Charge Pump Section OUT Output Voltage VOUT OUT Maximum Output Current IOUT(MAX) 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 Charge Pump Soft-Start Time tCP(SS) BL1-BL6, BL7/FL2, FL1 LED Drivers IBLx IBL_x I(BLx)/ IBL(AVG) VBL_(TH) tFADE IFL[1] IFL[1](DATA13) I(FLx)/ IFL(AVG) VFL[1/2](TH) tFL/tFL_SET BL1-BL7 Current Accuracy BL1-BL7 Current Accuracy BL1-BL7 Current Matching2 BL1-BL7 Charge Pump Transition Threshold BL1-BL7 Automatic Fade-In/Fade-Out Timer FL1 Current Accuracy FL1 Current Accuracy FL1-FL2 Current Matching (AAT2861-2 only) FL1 Charge Pump Transition Threshold Flash Safety Timer Period
140 15 5.2 800 0.3 1 1 100 18 1.6 20 2 3 0.2 0.75 540 108 1 600 120 5 0.45 1.5 2 2.5 1.25 660 132 22 2.4
VIN = 3.0V, VOUT = 4.0 EN/SET = IN; VIN - VF = 1V; ADDR = 0, DATA = 16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 EN/SET = FL_EN = IN; VIN - VF = 1V; ADDR = 10, DATA = 1 TA = 25C TA = 25C EN/SET = IN; VIN - VF = 1V; ADDR = 0, DATA = 16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 EN/SET = IN; VIN - VF = 1V; ADDR = 0, DATA = 16; ADDR = 3, DATA = 4; ADDR = 2, DATA = 14 EN/SET = IN; VIN - VF = 1V; ADDR = 0, DATA = 16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 EN/SET = IN; VIN - VF = 1V; ADDR=0, DATA = 16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 EN/SET = IN; VIN - VF = 1V; ADDR = 0, DATA = 16; ADDR = 1, DATA = 1; ADDR = 2, DATA = 12; ADDR = 3, DATA = 3 EN/SET = FL_EN = IN; VIN - VF = 1V; ADDR = 10, DATA = 1 EN/SET = FL_EN = IN; VIN - VF = 1V; ADDR = 10, DATA = 13 EN/SET = FL_EN = IN; VIN - VF = 1V, ADDR = 10, DATA = 1 EN/SET = FL_EN = IN; VIN - VF = 1V; ADDR = 10, DATA = 1 EN/SET = FL_EN = IN; VIN - VF = 1V; ADDR = 11, DATA = 1
mA mA % V s mA mA % V s
1. The AAT2861 is guaranteed to meet performance specifications over the -40C to +85C 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 current from the average of all active channels.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Electrical Characteristics (continued)1
VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol
Linear Regulators VLDO[A/B/C]/ VLDO[A/B/C] LDOA, LDOB, LDOC Output Voltage Tolerance ILDO = 1mA to 200mA; TA = 25C ILDO = 1mA to 200mA; TA = -40C to +85C VLDO[A/B/C] 3.0V; ILDO = 150mA VIN = (VLDO[A/B/C] + 1V) to 5V ILDO[A/B/C] = 10mA, 1kHz -1.5 -3.0 200 75 0.09 50 20 1.4 0.4 -1 1 500 500 75 50 75 150 1.5 3.0 % % mA mV %/V dB V V A s s s ns s
Description
Conditions
Min
Typ
Max
Units
ILDO[A/B/C](MAX) LDOA, LDOB, LDOC Load Current VLDO[A/B/C](DO) LDOA, LDOB, LDOC Dropout Voltage2 VLDO/ LDOA, LDOB, LDOC Line Regulation VLDO*VIN LDOA, LDOB, LDOC Power Supply Rejection Ratio PSRR[A/B/C] LDOA, LDOB, LDOC Auto-Discharge Resistance ROUT_(DCHG) EN/SET AS2Cwire and Logic Control EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input High VIH Threshold Voltage EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input Low VIL Threshold Voltage EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input LeakIIN(LKG) age Current EN/SET Input OFF Timeout tEN/SET(OFF) EN/SET Input Latch Timeout tEN/SET(LAT) EN/SET Input LOW Time tEN/SET(LOW) EN/SET Minimum High Time tENSET(H-MIN) EN/SET Maximum High Time tENSET(H-MAX)
2.7V VIN 5.5V 2.7V VIN 5.5V EN/SET = IN = 5V
0.3
1. The AAT2861 is guaranteed to meet performance specifications over the -40C to +85C 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.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
Backlight Efficiency vs. Input Voltage
100 90 100 90
Flash Efficiency vs. Input Voltage
Efficiency (%)
Efficiency (%)
80 70 60 50 40 30 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
80 70 60 50 40 30 2.7
30mA/ch, VF = 3.95V 15mA/ch, VF = 3.5V 4.2mA/ch, VF = 3.4V
320mA/ch, VF = 3.25V 160mA/ch, VF = 3.15V
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; 20mA/ch) Backlight Output Current (mA)
22 21 20 19 Channel 1 - Channel 6/7 18 17 16 -40
Charge Pump Output Turn On Characteristic
(VIN = 3.6V; 0mA/ch; COUT = 2.2F) Output Voltage (bottom) (V)
4.0
VEN/SET (top) (V)
2.0 0.0 4.0 3.0 2.0 1.0 0.0
-15
10
35
60
85
Temperature (C)
Time (50s/div)
Turn On to 1X Mode Flash
(VIN = 4.2V; 300mA/ch) VFL_EN (2V/div) VOUT (2V/div) VFLX (2V/div) IIN (200mA/div) Time (50s/div)
4 2 0 600 400 200 0 4 2 0
Turn On to 1.5X Mode Flash
(VIN = 3.6V; 300mA/ch)
4
VFL_EN (2V/div) VOUT (2V/div) VFLX (2V/div) IIN (200mA/div) Time (50s/div)
4 2 0
2 0
600 400 200 0
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2861.2009.02.1.2
PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
Turn On to 2X Mode Flash
(VIN = 2.8V; 300mA/ch)
4
Turn On to 1X Mode Backlight
(VIN = 3.6V; 20mA/ch) VEN/SET (2V/div)
0V
VFL_EN (2V/div) VOUT (2V/div) VFLX (2V/div) IIN (200mA/div) Time (50s/div)
4 2 0
2 0
VOUT (2V/div)
600 400 200 0
VSINK (2V/div)
0V
IIN (100mA/div)
0A
Time (200s/div)
Turn On to 1.5X Mode Backlight
(VIN = 3.2V; 20mA/ch) VEN/SET (2V/div)
0V
Turn On to 2X Mode Backlight
(VIN = 3.0V; 20mA/ch) VEN/SET (2V/div)
0V
VOUT (2V/div) VSINK (2V/div) IIN (200mA/div)
0V
VOUT (2V/div) VSINK (2V/div) IIN (200mA/div) Time (200s/div)
0V
0A
0A
Time (200s/div)
Turn Off from 1.5X Mode Backlight
(VIN = 3.2V; 20mA/ch) Input Voltage (AC coupled) (top) (mV)
Operating Characteristic
(VIN = 3.2V; 20mA/ch Backlight; 1.5x Mode; COUT = 2.2F) Charge Pump Output Voltage (AC coupled) (bottom) (mV)
20 10 0
VEN/SET (2V/div) VDIODE (2V/div) IIN (200mA/div)
50 0 -50
Time (200s/div)
Time (500ns/div)
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
Operating Characteristic
LDO Output Voltage Deviatoin (%) (VIN = 3.0V; 20mA/ch Backlight; 2X Mode; COUT = 2.2F) Charge Pump Output Voltage (AC coupled) (bottom) (mV) Input Voltage (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
LDO A/B/C Load Regulation
(VIN = 3.6V)
VOUT = 1.8V VOUT = 3.0V
Time (500ns/div)
Load Current (mA)
LDO A/B/C Output Voltage vs. Temperature
LDO Output Voltage Deviatoin (%) (VIN = 3.6V; ILDO = 0mA)
1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -40
LDO A/B/C Load Transient Response
(ILDO = 10mA to 200mA; VIN = 3.6V; VLDO = 1.8V; CLDO = 2.2F)
LDO Output Current (top) (mA)
VOUT = 1.8V VOUT = 3.3V
200 100 0 -100 -200 -300 -400 -500 2.00 1.90 1.80 1.70 1.60
LDO Output Voltage (bottom) (V)
-15
10
35
60
85
Temperature (C)
Time (20s/div)
LDO A/B/C Line Transient Response
(VIN = 3.6V to 4.2V; ILDO = 10mA; VOUT = 1.8V; CLDO = 2.2F)
4.4 4.0
LDO A/B/C Turn On Characteristic
(VLDO = 1.8V; VIN = 3.6V; CLDO = 2.2F) LDO Output (bottom) (V)
LDO Output Voltage (bottom) (V)
Input Voltage (top) (V)
4.0 3.6 1.82 1.81 1.80 1.79 1.78
VENLDOX (top) (V)
2.0 0.0 1.5 1.0 0.5 0.0
Time (1ms/div)
Time (20s/div)
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C High Threshold Voltage vs. Input Voltage
1.4
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Low Threshold Voltage vs. Input Voltage
1.2
VEN/SET(H), VFL_EN(H), VEN_LDOA(H), VEN_LDOB/C(H) (V)
VEN/SET(L), VFL_EN(L), VEN_LDOA(L), VEN_LDOB/C(L) (V)
1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5
1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3
-40C 25C 85C
-40C 25C 85C
0.4 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
0.2 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Input Voltage (V)
EN/SET Input Latch Timeout vs. Input Voltage
400 350 300 250 200 150 100 2.7
EN/SET Input Off Timeout vs. Input Voltage
500 450 400
TOFF (s)
-40C 25C 85C
3.1 3.5 3.9 4.3 4.7 5.1 5.5
TLAT (s)
350 300 250 200 150 100 2.7 3.1 3.5 3.9 4.3 4.7
-40C 25C 85C
5.1 5.5
Input Voltage (V)
Input Voltage (V)
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Functional Block Diagrams
AAT2861IMK-1-T1
IN IN
C1C1+ C2C2+
LDOA
1x/1.5x/2x Tri-mode Charge Pump
LDOB
OUT
8
LDOC
REF
BL1 EN/SET FL_EN 5
Main Backlight Current Control
BL2 BL3 BL4
EN_LDOA
Control Logic
5
BL5 EN_LDOB/C
Sub Backlight Current Control
BL6 BL7
4
Flash Control
FL1
PGND
AGND
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2861.2009.02.1.2
PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
AAT2861IMK-2-T1
IN IN
C1C1+ C2C2+
LDOA
1x/1.5x/2x Tri-mode Charge Pump
LDOB
OUT
8
LDOC
REF
BL1 EN/SET 5 Main Backlight Current Control BL2 BL3 BL4 EN_LDOA Control Logic 5 EN_LDOB/C Sub Backlight Current Control BL5 BL6
FL_EN
4
Flash Control
FL2 FL1
PGND
AGND
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
AAT2861IMK-3-T1
IN IN
C1C1+ C2C2+
LDOA
1x/1.5x/2x Tri-mode Charge Pump
LDOB
OUT
8
LDOC
REF
BL1 EN/SET 5 BL2 Main Backlight Current Control BL3 BL4 EN_LDOA Control Logic 5 BL5
FL_EN
EN_LDOB/C
Sub Backlight Current Control Flash Control
BL6 BL7
4
FL1
PGND
AGND
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2861.2009.02.1.2
PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
imately 1mA steps while the flash LED current can be set between 0 and 600mA in 40mA steps or 0 to 300mA in 20mA steps for two channel flash version. The backlight LED currents match to within 3% while the flash LED currents match to within 5%. To eliminate the latency of the AS2Cwire serial interface, the flash LED is enabled through a dedicated input, FL_EN. The AAT2861 also includes a safety timer that prevents thermal 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 fail to turn 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 AS2Cwire serial interface as are the backlight fade-in/fade-out timer and the flash safety timer. See the "AS2Cwire Serial Interface Programming" section of this datasheet for more information on setting the LED currents.
Functional Description
The AAT2861 is a highly integrated backlight and photoflash driver family 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 are powered from the same input and produce regulated output voltage between 1.2V and 3.3V. Control of the LEDs and the LDO output voltage is through an AS2Cwire serial interface for easy programming.
LED Drivers
The AAT2861 drives six or seven backlight LEDs up to 31mA each and a total of 600mA flash current through one or two channels. 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, to 1.5X, to 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 1F ceramic capacitors. Each individual LED is driven by a current sink to GND, allowing individual current control with high accuracy over a wide range of input voltages and LED forward voltages while maintaining high efficiency. The charge pump is controlled by the voltage across the LED current sinks. When any one of the active backlight current sink/channel voltages drops below 200mV 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 AAT2861 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 300mV mode-transition hysteresis that prevents the charge pump from oscillating between modes.
LDO Regulators
The AAT2861 includes three low dropout (LDO) linear regulators. These regulators are powered from the battery and produce a fixed output voltage set through the AS2Cwire serial interface. The output voltage can be set to one of 16 output voltages between 1.2V and 3.3V. The LDO regulators can be turned on/off with the external enable pins EN_LDOA and EN_LDOB/C. Additionally, the AS2Cwire interface allows the LDO regulators to be enabled independently when the EN_LDOA and EN_ LDOB/C pins are pulled high. The LDO regulators require only a small 2.2F ceramic output capacitor for stability. If improved load transient response is required, larger-valued capacitors can be used without stability degradation.
AS2Cwire Serial Interface Protocol
The AAT2861 is dynamically programmable by the AS2Cwire single-wire interface. AS2Cwire records rising edges detected at the EN/SET pin to address and load the data registers. The timing diagram in Figure 1 shows the typical transmission protocol.
LED Current Control
Both the backlight and flash LED currents are controlled through the AS2Cwire serial interface. The backlight LED current can be set between 0.5mA and 31mA in approx-
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Address
THI TLO TLAT TLAT
Data
EN/SET
1 2 17 18 1 2... n <= 16
Address
0
1
Data Reg 1
0
n
Data Reg 2
0
Figure 1: AS2Cwire Serial Interface Timing Diagram. AS2Cwire latches data or address after the EN/SET input has been held high for time tLAT (500s). Address or data is differentiated by the number of EN/SET rising edges. Since the data registers are 4 bits each, the differentiating number of pulses is 24 or 16, so that Address 0 is identified by 17 rising edges, Address 1 by 18 rising edges, Address 2 by 19 rising edges, etc. Data is set to any number of rising edges between 1 and 16. A typical write protocol is a burst of EN/SET rising edges identifying a particular address, followed by a pause with EN/SET held high for the tLAT timeout period, then a burst of rising edges signifying data, and another tLAT timeout after the data has been sent. Once an address is set, multiple writes to that address are allowed since the address is not reset after each write. Address edges are needed when changing the address, or writing to an address other than the default after shutdown. Address 0 is the default address after shutdown. If the part is enabled with only data edges and no address, then Address 0 will be programmed and LED Backlight channels BL1-BL7 will be enabled according to the number of data edges applied. When EN/SET is held low for a time longer than tOFF (500s), the AAT2861 enters shutdown mode and draws less than 1A of current from IN. At shutdown, the data and address registers are reset to 0.
Backlight Current Control (Address 0)
Address 0 controls the enabling of the Main and Sub channels. Table 2 shows the Data Codes used to control the Main and Sub Channels independently. The default condition for all backlight outputs (BL1-BL7) is OFF after power-up. The AAT2861 family of LMUs also provides an internal LED current fade-in, fade-out feature. This feature is useful in those applications where it is preferred to turn on and off the backlight current using a smooth transition versus an abrupt transition. During the fade-in cycle, the LED current will be slowly increased to the programmed current level (set in Addresses 2 to 5). During the fade-out cycle, the LED current will be decreased linearly down to its programmed fade-out current threshold (set by Address 1) at which point the BL channels will be turned off. The fade-in and fade-out current is a linear transition over a time period of approximately 1 second. The fade-in and fade-out function can be enabled and disabled independently for the Main and Sub groups by writing the desired Data to Address 0. Table 2 also lists the data codes used to program enable and disable the fade functions for the main and sub channels. If the "Main Equals Sub" feature (Address 3) is enabled (MEQS=1), the fade-in and fade-out settings for the Main and Sub channels are controlled by the "Main Fade" setting and the "Sub Fade" bit in Address 1 will be ignored. At startup when the EN/SET pin is first pulled high, Address 0 is the default active register. The main and sub channels can be turned on by immediately writing data. For example, if Data = 4 is written the main and sub channels will turn on to the default value of 19mA.
AS2Cwire Serial Interface Programming
The AAT2861's AS2Cwire programmable Address registers are listed in Table 1. There are 14 Address registers, four registers control the three LDOs, six control the backlight LED configuration, two control the flash/lamp LED configuration and two are used to individually disable each backlight or flash channel.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM
Address
0 1 2 3 4 5 6 7 8 9 10 11 12 13
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Function
Backlight Main/Sub ON/OFF and Fade Enable Backlight Fade Control Backlight Current Main, LSB's Backlight Current Main, MSB Backlight Current Sub, LSB's Backlight Current Sub, MSB LDO Disable Control LDO A Output Voltage Control LDO B Output Voltage Control LDO C Output Voltage Control Flash Current Flash Timer Control LED Channel Disable Control (BL1 - BL4) LED Channel Disable Control (BL5, BL6, BL7/FL2, FL1)
EN/SET Rising Edges
17 18 19 20 21 22 23 24 25 26 27 28 29 30
D3
FADE_SUB X BLM[3] Reserved BLS[3] X X LDOA[3] LDOB[3] LDOC[3] F_HI[3] X OFF_BL4 OFF_FL1
D2
FADE_MAIN X BLM[2] X BLS[2] X OFF_LDOC LDOA[2] LDOB[2] LDOC[2] F_HI[2] X OFF_ BL3 OFF_BL7/FL2
D1
SUB_ON FLOOR[1] BLM[1] MEQS BLS[1] X OFF_LDOB LDOA[1] LDOB[1] LDOC[1] F_HI[1] F_TIME[1] OFF_ BL2 OFF_BL6
D0
MAIN_ON FLOOR[0] BLM[0] BLM[4] BLS[0] BLS[4] OFF_LDOA LDOA[0] LDOB[0] LDOC[0] F_HI[0] F_TIME[0] OFF_ BL1 OFF_BL5
Table 1: AAT2861- 1 Configuration/Control Register Allocation (* signifies that the data bit has a POR default bit value = 1; X signifies "Don't care"). current threshold (set by Address 1) at which point the BL channels will be turned off. The default fade-out current level is 500A, but can be changed to 1mA, 2mA or 3mA using the data codes listed in Table 3. Data
1* 2 3 4
Data
1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Sub Fade On
No* No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes
Main Fade On
No* No No No Yes Yes Yes Yes No No No No Yes Yes Yes Yes
Sub Channel
Off* Off On On Off Off On On Off Off On On Off Off On On
Main Channel
Off* On Off On Off On Off On Off On Off On Off On Off On
Fade Out Current Level (mA)
0.50* 1.0 2.0 3.0
Table 3: Backlight Fade-In and Fade-Out Control (Address 1).
Backlight Current Control (Addresses 2 to 5)
The AAT2861's AS2Cwire Addresses 2, 3, 4, and 5 control the backlight LED output current level in Main and Sub group of outputs. Address 2 and Address 3 control the Main backlight channel current to one of 32 levels according to Table 4 below. Address 3 acts as the MSB and Address 2 acts as the LSB for the current level setup. Address 4 and Address 5 control the Sub backlight channels current to one of 32 levels according to Table 5 below.
Table 2: Backlight Main/Sub ON/OFF and Fade Enable (Address 0).
Backlight Fade-In and Fade-Out Control (Address 1)
During the fade-out cycle, the LED current will be decreased linearly down to its programmed fade-out
*Denotes the default (power-on-reset) value
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Main Equals Sub ON (MEQS=1)
Address 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Data 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Address 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Main Current 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0.5 31 30 29 28 27 26 25 24 23 22 21 20* 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0.5
Main Equals Sub OFF (MEQS=0)
Address 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Data 1 1 1 1 1 1 1 1 1 1 1 1* 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Address 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Data 1 2 3 4 5 6 7 8 9 10 11 12* 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Main Current
Table 4: Backlight Main Current Control (Addresses 2 and 3).
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Sub Backlight
Address 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Data 1 1 1 1 1 1 1 1 1 1 1 1* 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Address 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Data 1 2 3 4 5 6 7 8 9 10 11 12* 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sub Current 31 30 29 28 27 26 25 24 23 22 21 20* 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0.5
For example, a change from 28mA to 8mA in the Main backlight channels should follow this procedure. First, 28mA is set by programming Data = 3 to Address 2 and Data=1 to Address 3. When changing to 8mA first write Data=2 to Address 3. The current level will not change after this step. Then write Data=7 to Address 2. After Address 2 has been latched the new 8mA current level will be set. Address 3 also controls the "Main Equals Sub" feature in the AAT2861 products. This feature allows all backlight channels to be controlled with only the Main Channel current settings. If the "Main Equals Sub" feature is turned on (Data 3, or 4 in Address 3) the current settings of the Sub Channel are ignored. All backlight channels will be set to the same current levels as determined by the Data programmed to "Backlight Current Main" in Addresses 2 and 3. The Main and Sub channels are turned on and off by the "Main On" setting in Address 0. The default condition is for the "Main Equals Sub" feature to be turned OFF (MEQS=0) after power-up. Table 6 shows the Main and Sub Channel Configurations for the three versions of the AAT2861. The effect of the "Main Equals Sub" feature is clearly represented in this table. Main Equals Sub (IMAIN = ISUB) Part Number
AAT2861-1 AAT2861-2 AAT2861-3 Yes (Default) 7M+0S+1FL 6M+0S+2FL 7M+0S+1FL No 4M+3S+1FL 4M+2S+2FL 5M+2S+1FL
Table 6: Main and Sub Channel Configurations.
Table 5: Backlight Sub Current Control (Addresses 4 and 5). The current settings for the Main and Sub channels are each divided into two Addresses. Any change in Data to the "Backlight Current Main (or Sub), LSB's" Address will result in an immediate change to the LED current output level. Programming new current settings that require a change to both "Backlight Current Main (or Sub), MSB" and "Backlight Current Main (or Sub), LSB's" Addresses could result in an errant intermediate current setting. To avoid this problem when the Data in "Backlight Current Main (or Sub), MSB" Address is changed the new current setting will not take effect until "Backlight Current Main (or Sub), LSB's" Address has been written to and latched.
LDO Output Voltage Control (Addresses 6 to 9)
The AAT2861's three LDO regulators are configured by programming Addresses 6, 7, 8, and 9 via the AS2Cwire interface. With the EN/SET pin pulled high and the AAT2861 turned on, LDOA can be enabled using the EN_ LDOA pin. LDOB and LDOC can be enabled together using the EN_LDOB/C pin. Additional LDO regulator control can be achieved using Address 6 to override the enable command of the EN_LDOA and EN_LDOB/C pins. For example, with the EN_LDOA and EN_LDOB/C pins enabled, writing Data 5 to Address 6 will disable LDOB and leave LDOA and LDOC enabled. Table 7 shows the LDO disable control. Writing data to Addresses 7, 8, and 9 set the output voltages for LDOA, LDOB, and LDOC to one of 16 levels. The available LDO output voltages are shown in Table 8.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM
Data
1* 2 3 4 5 6 7 8
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
LDO B
Controlled by EN_LDOB/C* Controlled by EN_LDOB/C OFF OFF Controlled by EN_LDOB/C Controlled by EN_LDOB/C OFF OFF
LDO C
Controlled by EN_LDOB/C* Controlled by EN_LDOB/C Controlled by EN_LDOB/C Controlled by EN_LDOB/C OFF OFF OFF OFF
LDO A
Controlled by EN_LDOA* OFF Controlled by EN_LDOA OFF Controlled by EN_LDOA OFF Controlled by EN_LDOA OFF
Flash Driver Control (Address 10 and 11)
The AAT2861-1 and AAT2861-3 are both configured with a single 600mA LED Flash channel, while the AAT2861-2 is configured with two LED Flash channels each capable of driving 300mA per channel. Address 10 programs the flash current level. Table 9 lists the data codes for the programming Address 10. Upon startup, the power-onreset value in Address 10 is set to data code 13. Flash Current (mA) per Output Data
1 2 3 4 5 6 7 8 9 10 11 12 13* 14 15 16 AAT2861-1 or -3 600 560 520 480 440 400 360 320 280 240 200 160 120* 80 40 OFF AAT2861-2 300 280 260 240 220 200 180 160 140 120 100 80 60* 40 20 OFF
Table 7: LDO Disable Control (Address 6). Data
1 2 3 4 5* 6 7 8 9 10 11 12 13 14 15 16
VLDOA (V)
1.2 1.3 1.5 1.6 1.8* 2 2.2 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3
VLDOB (V)
1.2 1.3 1.5 1.6 1.8* 2 2.2 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3
VLDOC (V)
1.2 1.3 1.5 1.6 1.8* 2 2.2 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3
Table 9: Flash Current Level (Address 10). Once the EN/SET pin is pulled high and the AAT2861 has turned on, the LED Flash channels can be enabled by pulling the FL_EN to IN. The current setting of the LED Flash channels can be changed prior to enabling the flash current, or while the flash current is on. The LED Flash controller also comes with a safety timer to prevent excessive heat generation and power loss from extended high current power dissipation. The LED flash safety timer duration can be set to four values by writing to Address 11. The default value at startup is 2 seconds. Table 10 shows the Data Codes for the flash safety timer.
Table 8: LDO X Output Voltage (Addresses 7, 8, and 9). Fast turn-off response time is achieved by an active output pull-down circuit, which is enabled when the LDO regulator is disabled.
*Denotes default (power-on-reset) value.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
LED Channel Disable Control (Address 12 and 13)
Addresses 12 and 13 allow for additional programming flexibility by allowing each LED channel to be independently disabled. Normally, the backlight channels are controlled by MAIN_ON and SUB_ON controls in Address 0, while the FL_EN pin turns on the flash channels. Writing to Addresses 12 and 13 can override these controls to allow for any combination of LEDs to be turned on. The default state is for all LED channels to be "Conditionally ON" to allow the normal enable control. In the following example we see how to turn on BL1, BL2, BL6, and BL7 in the AAT2861-1 (4M+3S+1FL). First write Address 12, Data=13 and Address 13, Data=10 to disable BL3, BL4, BL5, FL1. Then program the desired current setting using Addresses 2 through 5. Finally, write Address 0, Data=4. (NOTE: "Conditionally ON" state allows the LED channel to be turned ON but does not turn the channel ON. For BL1 to be enabled Data=2, 4, 6, 8... must be written to Address 0, and Data=1, 3, 5, 7... must be written to Address 12.) Torch/movie mode is automatically entered when the flash current setting is programmed to 120mA (60mA for channel for the AAT2861-2) or lower with Data = 13, 14, or 15. At these current levels the safety timer is automatically disabled and the flash channels will remain on as long as the FL_EN pin remains active. Extended duration flash use can be achieved for higher current settings by writing Data 4 to Address 11 to disable the safety timer. Though the AAT2861 includes an internal thermal limit circuit, be careful to limit the current setting (Address 10) to a value that will not generate excessive heat which may damage the flash LEDs or external circuitry. Data
1* 2 3 4
Flash Time (sec)
2* 1 0.5 Always ON
Table 10: Flash Safety Timer (Address 11).
Data
1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
BL4
Conditionally ON* Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF OFF OFF OFF OFF
BL3
Conditionally ON* Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF Conditionally ON Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF
BL2
Conditionally ON* Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF
BL1
Conditionally ON* OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF
Table 11: LED Channel Individual Disable Control, BL1-BL4 (Address 12).
*Denotes default (power-on-reset) value.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM
Data
1* 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
FL1
Conditionally ON* Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF OFF OFF OFF OFF
BL7/FL2
Conditionally ON * Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF Conditionally ON Conditionally ON Conditionally ON Conditionally ON OFF OFF OFF OFF
BL6
Conditionally ON* Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF Conditionally ON Conditionally ON OFF OFF
BL5
Conditionally ON* OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF Conditionally ON OFF
Table 12: LED Channel Individual Disable Control, BL5, BL6, BL7/FL2, FL1 (Address 13).
Applications Information
LED Selection
The AAT2861 is specifically intended for driving white LEDs. However, the device design will allow the AAT2861 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 BL6, BL7/ FL2 and FL1 constant current sinks are matched with negligible voltage dependence, the constant current channels will be matched regardless of the specific LED forward voltage (VF) levels. The low-dropout current sinks in the AAT2861 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.
Device Switching Noise Performance
The AAT2861 operates at a fixed 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. Back-injected noise appearing on the input pin of the charge pump is 20mV peak-to-peak, typically ten times less than inductor-based DC/DC boost converter white LED backlight solutions. The AAT2861 soft-start feature prevents noise transient effects associated with in-rush currents during the start up of the charge pump circuit.
Device Power Efficiency
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 AAT2861, it is very difficult to measure efficiency in terms of a percent value comparing input power over output power.
*Denotes default (power-on-reset) value.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
The AAT2861 charge pump is a fractional charge pump which will boost the input supply voltage in the event where IN 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 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 () for the AAT2861 in 1.5x mode is as follows: Since the AAT2861 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 BL6, BL7/FL2, and FL1) 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 AAT2861 efficiency may be quantified under very specific conditions and is dependant upon the input voltage versus the output voltage seen across the loads applied to outputs BL1 through BL6, BL7/FL2 or FL1 for a given constant current setting. Depending on the combination of IN and voltages sensed at the current sinks, the device will operate in "Load Switch" (1X) mode. When any one of the voltages sensed at the current sinks 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. AAT2861 charge pump conversion efficiency is defined as the power delivered to the white LED load divided by the input power:
=
=
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 = 1.5V
The same calculations apply for the AAT2861 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 () for the AAT2861 in 2x mode is as follows:
=
=
PLEDs VLED1 * ILED1 + ... + VLEDX * ILEDX = PIN VIN * IIN
X * VLEDX * ILEDX ; X = 1, 2, 3, ..., 6 or 7 and IIN = 2(X * ILEDX) VIN * IIN
VLEDX = 2V IN
In addition, with an ideal 1.5x charge pump, the output current may be expressed as 2/3 of the input current. For a charge pump with an output of 5V and a nominal input of 3.5V, the theoretical efficiency is 95%. Due to internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%. Efficiency will decrease substantially as load current drops below 1mA or when the level of IN approaches OUT. The same calculations apply for 2X mode where the output current then becomes 1/2 of the input current.
=
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 The expression to define the estimated ideal efficiency () for the AAT2861 in 1X mode is as follows:
=
PLEDs X * VLEDX * ILEDX = PIN VIN * IIN
Capacitor Selection
Careful selection of all external capacitors CIN, C1, C2, CLDO(A/B/C), and COUT is important because they will affect turn-on time, output ripple and transient performance. Optimum performance will be obtained when low ESR
X = 1, 2, 3, ..., 6 or 7 and IIN = X * ILEDX VLEDX = V IN
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
These larger size capacitors can improve circuit transient response when compared to an equal value capacitor in a smaller package size. ceramic capacitors are used. In general, low ESR may be defined as less than 100m. Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the AAT2861. Ceramic capacitors offer many advantages over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is lowest cost, has a smaller printed circuit board (PCB) footprint, and is non-polarized. Since ceramic capacitors are non-polarized, they are not prone to incorrect connection damage.
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 2 and 3 illustrate an example PCB layout. The bottom of the package features an exposed metal paddle. The exposed paddle acts, thermally, to transfer heat from the chip and, electrically, as a ground connection. The junction-to-ambient thermal resistance (JA) 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 re-flow process. Multiple copper plated thru-holes should be used to electrically and thermally connect the top surface paddle area to additional ground plane(s) and/or the bottom layer ground pour. The chip ground is internally connected to both the paddle and to the AGND and PGND pins. It is good practice to connect the GND pins to the exposed paddle area with traces as shown in the example. The flying capacitors C1 and C2 should close to the IC. Trace length should be minimize path resistance and potential input and output capacitors should also close to the chip as possible. be connected kept short to coupling. The be placed as
Equivalent Series Resistance (ESR)
ESR is an important characteristic to consider when selecting a capacitor. ESR is a resistance internal to a capacitor, which is caused by the leads, internal connections, size or area, material composition and ambient temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more than several ohms for tantalum or aluminum electrolytic capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F are typically made from NPO or COG materials. NPO and C0G materials typically have tight tolerance and are stable over temperature. Larger capacitor values are typically composed of X7R, X5R, Z5U or Y5V dielectric materials. Large ceramic capacitors, typically greater than 2.2F are often available in low cost Y5V and Z5U dielectrics, but capacitors greater than 1F are typically not required for AAT2861 applications. Capacitor area is another contributor to ESR. Capacitors that are physically large will have a lower ESR when compared to an equivalent material smaller capacitor.
Manufacturer
AVX TDK Murata Taiyo Yuden
Part Number
0603ZD105K 0603ZD225K C1608X5R1E105K C1608X5R1C225K C1608X5R1A475K GRM188R61C105K GRM188R61A225K LMK107BJ475KA
Value
1F 2.2F 1F 2.2F 4.7F 1F 2.2F 4.7F
Voltage
10 10 25 16 10 16 10 10
Temp. Co.
X5R X5R X5R X5R
Case
0603 0603 0603 0603
Table 13: Surface Mount Capacitors.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
The evaluation board is made flexible so that the user can disconnect the enable line from the microcontroller and apply external enable signal. External enable signal must be applied to the EN/SET pin. When applying external enable signal, consideration must be given to the voltage levels. The externally applied voltage should not exceed the supply voltage that is applied to the IN pins of the device (DC+). The LDO loads can be connected directly to the evaluation board. For adequate performance, be sure to connect the load between LDOA/LDOB/LDOC and DC- as opposed to some other GND in the system.
Evaluation Board User Interface
The user interface for the AAT2861 evaluation board is provided by four buttons and a number of connection terminals. The board is operated by supplying external power and pressing individual buttons or button combinations. Table 14 indicates the function of each button or button combination. To power-on the evaluation board, connect a power supply or battery to the DC- and DC+ terminals. A red LED indicates that power is applied.
Button(s) Pushed
SW1
Description
[Push/Release once] LDOA, LDOB and LDOC outputs are programmed to 1.2V. With every subsequent push/release LDOA, LDOB and LDOC output voltages are incremented according to Table 8. [Push/hold more than 2 sec] LDOA, LDOB and LDOC outputs will start to cycle through all programmable voltage settings according to Table 8. [Push/Release once] All channels are turned on as Main backlight with 31mA per channel. With every subsequent push/release the backlight current is decreased according to Table 4. [Push/hold more than 2 sec] All channels Main and Sub are turned on with 31mA per channel and fade out sequence is initiated. The cycle proceeds with fade in for Main channels only, followed by fade in sequence for Sub channels. When these sequences are finished the program will restart fade out sequence for all Main and Sub channels. [Push/Release once] Flash channels are programmed with maximum current and timer. With every subsequent push/release the flash current is decreased according to Table 9. The FLASH button needs to be pressed down simultaneously. This button is connected directly to FL_EN pin. Press and hold for the flash to be enabled.
SW2
SW3 FLASH
Table 14: AAT2861 Evaluation Board User Interface.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
OUT DC+ IN R5 0 C1 1.0F DF1 D7 DF2 C2 1.0F
1
C4 4.7F
U1 AAT2861-X C1+ IN C1- C2- PGND
24 23 22 21 20
D6 D5 D4 D3 D2 D1
OUT C2+ EN/SET FL_EN EN_LDOA EN_LDOB/C AGND LDOC
8
FL1 BL7/FL2 BL6 BL5 BL4 BL3 BL2 IN
9
19 18 17 16 15 14 13
C8 2.2F
2 3 4 5
FLASH
5 41 32
6 7
DC+
R4 10K
LDOB LDOA BL1
10 11 12
C7 2.2F
C5 4.7F
C6 2.2F
C3 2.2F
R7 10K R1 1K
5 4 3 5 4 3 5 4 3 1 2 1 2 1 2
DC+ DC+ R2 1K R3 1K
1 2 3 4
SW1 SW2 SW3
U3 VDD VSS GP5 GP0 GP4 GP1 GP3 GP2 PIC12F675
8 7 6 5
C9 1F
R6 330 LED7 RED
Figure 2: AAT2861 Evaluation Board Schematic.
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2861.2009.02.1.2
PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Figure 3: AAT2861 Evaluation Board Top Side Layout.
Figure 4: AAT2861 Evaluation Board Bottom Side Layout.
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PRODUCT DATASHEET
AAT2861
ChargePumpTM
Component
U1 U2 D1-D7 DF1, DF2 C1, C2 C3, C6, C7, C8 C4, C5 R1-R3 R4 R6 R5 LED7 SW1-SW3, FLASH
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Part#
AAT2861IMK-x-T1 PIC12F675 LW M673 LXCL PWF1 GRM18x GRM18x GRM18x Chip Resistor Chip Resistor Chip Resistor Chip Resistor CMD15-21SRC/TR8 PTS645TL50
Description
High Eff. 1X/1.5X/2X CP for White LED, Triple LDO 8-bit CMOS, FLASH MCU; 8-pin PDIP Mini TOPLED White LED; SMT Mini TOPLED Flash LED; SMT 1.0F, 10V, X5R, 0603, Ceramic 2.2F, 10V, X5R, 0603, Ceramic 4.7F, 10V, X5R, 0603, Ceramic 1K, 5%, 1/4W; 0603 10K, 5%, 1/4W; 0603 330, 5%, 1/4W; 1206 0, 5%, 1/4W; 1206 Red LED; 1206 Switch Tact, SPST, 5mm
Manufacturer
AnalogicTech Microchip OSRAM Lumileds, Philips Murata Murata Murata Vishay Vishay Vishay Rohm Chicago Miniature Lamp ITT Industries
Table 15: AAT2681 Evaluation Board Bill of Materials (BOM),
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2861.2009.02.1.2
PRODUCT DATASHEET
AAT2861
ChargePumpTM Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
Ordering Information
Package
TQFN34-24 TQFN34-24 TQFN34-24
Marking1
4KXYY 4LXYY 4XXYY
Part Number (Tape and Reel)2
AAT2861IMK-1-T1 AAT2861IMK-2-T1 AAT2861IMK-3-T1
All AnalogicTech products are offered in Pb-free packaging. The term "Pb-free" means semiconductor products that are in compliance with current RoHS standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more information, please visit our website at http://www.analogictech.com/about/quality.aspx.
Package Information
TQFN34-243
3.000 0.050 Index Area 1.700 0.050
0.210 0.040
0.400 0.050
2.700 0.050
4.000 0.050
R(5x)
0.400 BSC
Detail "A"
Detail "A" Top View Bottom View
0.750 0.050
0
+ 0.10 - 0.00
0.203 REF
Side View
All dimensions in millimeters. 1. XYY = assembly and date code. 2. Sample stock is generally held on part numbers listed in BOLD. 3. The leadless package family, which includes QFN, TQFN, DFN, TDFN, and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
Advanced Analogic Technologies, Inc. 3230 Scott Boulevard, Santa Clara, CA 95054 Phone (408) 737-4600 Fax (408) 737-4611
(c) Advanced Analogic Technologies, Inc. AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech's terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
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