AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 1
www.analogictech.com
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 sin-
gle-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 AS2Cwire™ (Advanced
Simple Serial Control™) 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 cur-
rent 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 low-
noise MicroPower™ LDO linear regulators. The regulators
output voltages are set through the AS2Cwire serial
interface. Each LDO can supply up to 300mA load cur-
rent 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 -40°C to
+85°C ambient temperature range.
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
• -40°C to +85°C Temperature Range
• TQFN34-24 Package
Applications
• Camera Enabled Mobile Devices
• Digital Still Cameras
• Multimedia Mobile Phones
Typical Application
CF1
1µF
CF2
1µF
C1+ C1- C2+ C2-
IN
COUT
2.2µF
VOUT
OUT
BL1
BL2
BL3
BL4
BL7/FL2
VLDOA
at 300mA
LDOA
CLDOA
2.2µF
VBAT
3.6V AAT2861-x
AGND
BL5
BL6
EN/SETEN/SET
FL_EN
FL_EN
CIN
2.2µF
LDOB
CLDOB
2.2µF
LDOC
CLDOC
2.2µF
PGND
VLDOB
at 300mA
VLDOC
at 300mA
EN_ LDOAEN_ LDOA
EN_LDOB/CEN_ LDOB/C
WLEDs
OSRAM LW M673
or equivalent
IN
Flash LEDs
Lumiled LXCL-PWF1
or equivalent
FL1
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2 2861.2009.02.1.2
www.analogictech.com
Pin Descriptions
Pin # Symbol Description
1 OUT
Charge pump output. OUT is the output of the charge pump and supplies current to the backlight and fl ash
LEDs. Connect the backlight and fl ash LED anodes to OUT. Bypass OUT to PGND with a 2.2F or larger
ceramic capacitor as close to the AAT2861 as possible.
2 C2+ Positive terminal of charge pump capacitor 2. Connect the 1F charge pump capacitor 2 from C2+ to C2-.
3 EN/SET AS2Cwire serial input. EN/SET is the address and data input of the AS2Cwire serial interface. AS2Cwire is
used to control backlight, fl ash and LDO functions.
4 FL_EN Flash enable. FL_EN is the enable control for the Flash LEDs. For the FL_EN pin to enable the fl ash current,
the EN/SET pin must also be pulled high.
5 EN_LDOA 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.
6 EN_LDOB/C
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.
7 AGND Analog ground. Connect AGND to PGND at a single point as close to the AAT2861 as possible.
8 LDOC 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.
9 IN Input power pin for all three LDOs. Connect Pin 9 to Pin 23 with as short a PCB trace as practical.
10 LDOB 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.
11 LDOA 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.
12 BL1 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.
13 BL2 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.
14 BL3 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.
15 BL4 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.
16 BL5 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.
17 BL6 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.
18 BL7 (FL2)
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.
19 FL1 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.
20 PGND Power ground. Connect PGND to AGND at a single point as close to the AAT2861 as possible.
21 C2- Negative terminal of charge pump capacitor 2.
22 C1- Negative terminal of charge pump capacitor 1.
23 IN 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.
24 C1+ Positive terminal of charge pump capacitor 1. Connect the 1F charge pump capacitor 1 from C1+ to C1-.
EP Exposed paddle (bottom) Connect to PGND/AGND.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 3
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 3
www.analogictech.com
Pin Configuration
TQFN34-24
(Top View)
1
2
3
4
5
6
7
8
9
24 23 22 21 20
10 11 12
19
18
17
16
15
14
13
OUT
C2+
EN/SET
FL_EN
EN_LDOA
EN_LDOB/C
AGND
LDOC
IN
LDOB
LDOA
BL1
BL5
BL6
BL4
BL3
BL2
BL7 (FL2)
FL1
PGND
C2-
C1-
IN
C1+
Part Number Descriptions1
Part Number
Backlight LED Outputs
Flash LED OutputsMain Sub
AAT2861IMK-1-T1 4 3 1
AAT2861IMK-2-T1 4 2 2
AAT2861IMK-3-T1 5 2 1
Absolute Maximum Ratings2
Symbol Description Value Units
IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6, BL7/FL2, FL1 Voltage to AGND -0.3 to 6.0 V
C1+, C2+ Voltage to AGND -0.3 to VOUT + 0.3 V
C1-, C2-, LDOA, LDOB, LDOC, EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Voltage to AGND -0.3 to VIN + 0.3 V
PGND Voltage to AGND -0.3 to 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C
Thermal Information3,4
Symbol Description Value Units
PDMaximum Power Dissipation 2.0 W
θJA Maximum Thermal Resistance 50 °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 25°C ambient temperature.
4. Mounted on a FR4 circuit board.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
4 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
4 2861.2009.02.1.2
www.analogictech.com
Electrical Characteristics1
VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =
25°C.
Symbol Description Conditions Min Typ Max Units
VIN IN Operating Voltage Range 2.7 5.5 V
IIN
IN Operating Current (1x mode, Main
Channels enabled, IBLX not included)
EN/SET = IN, BL1-BL7 = IN, FL_EN =
EN_LDOA = EN_LDOB/C = AGND 600 A
IN Operating Current (2x mode, Main
Channels enabled, IBLX not included)
2X Mode; EN/SET = IN, FL_EN = EN_LDOA =
EN_LDOB/C = AGND; BL1-BL7 = OPEN 5.5 mA
IN Operating Current (LDOA, LDOB and
LDOC enabled)
EN/SET = EN_LDOA = EN_LDOB/C = IN; FL_EN
= AGND; ADDR = 3; DATA = 1; No Load 225 A
IN Operating Current (Only LDOA
enabled)
EN/SET = EN_LDOA = IN; FL_EN = EN_LDOB/C
= AGND, ADDR = 3; DATA = 1; No Load 80 A
IIN(SHDN) IN Shutdown Current EN/SET, FL_EN, EN_LDOA, EN_LDOB/C = AGND 1.0 A
TSD Over-Temperature Shutdown Threshold 140 °C
TSD(HYS) Over-Temperature Shutdown Hysteresis 15 °C
Charge Pump Section
VOUT OUT Output Voltage 5.2 V
IOUT(MAX) OUT Maximum Output Current VIN = 3.0V, VOUT = 4.0 800 mA
VIN(TH_H, BL)
BL1-BL7 Charge Pump Mode Transition
Hysteresis
EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =
16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 0.3 V
VIN(TH_H, FL)
FL1-FL2 Charge Pump Mode Transition
Hysteresis
EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =
10, DATA = 1 1V
fOSC Charge Pump Oscillator Frequency TA = 25°C 1 MHz
tCP(SS) Charge Pump Soft-Start Time TA = 25°C 100 s
BL1-BL6, BL7/FL2, FL1 LED Drivers
IBLx BL1-BL7 Current Accuracy EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =
16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 18 20 22 mA
IBL_x BL1-BL7 Current Accuracy EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =
16; ADDR = 3, DATA = 4; ADDR = 2, DATA = 14 1.6 2 2.4 mA
I(BLx)/
IBL(AVG)
BL1-BL7 Current Matching2 EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =
16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 3%
VBL_(TH)
BL1-BL7 Charge Pump Transition
Threshold
EN/SET = IN; VIN – VF = 1V; ADDR=0, DATA =
16; ADDR = 3, DATA = 3; ADDR = 2, DATA = 12 0.2 V
tFADE
BL1-BL7 Automatic Fade-In/Fade-Out
Timer
EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =
16; ADDR = 1, DATA = 1; ADDR = 2, DATA =
12; ADDR = 3, DATA = 3
0.75 1 1.25 s
IFL[1] FL1 Current Accuracy EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =
10, DATA = 1 540 600 660 mA
IFL[1](DATA13) FL1 Current Accuracy EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =
10, DATA = 13 108 120 132 mA
I(FLx)/
IFL(AVG)
FL1-FL2 Current Matching (AAT2861-2
only)
EN/SET = FL_EN = IN; VIN – VF = 1V, ADDR =
10, DATA = 1 5%
VFL[1/2](TH) FL1 Charge Pump Transition Threshold EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =
10, DATA = 1 0.45 V
tFL/tFL_SET Flash Safety Timer Period EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =
11, DATA = 1 1.5 2 2.5 s
1. The AAT2861 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
2. Current matching is defined as the deviation of any sink current from the average of all active channels.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 5
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 5
www.analogictech.com
Electrical Characteristics (continued)1
VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =
25°C.
Symbol Description Conditions Min Typ Max Units
Linear Regulators
VLDO[A/B/C]/
VLDO[A/B/C]
LDOA, LDOB, LDOC Output Voltage Tolerance
ILDO = 1mA to 200mA; TA = 25°C -1.5 1.5 %
ILDO = 1mA to 200mA;
TA = -40°C to +85°C -3.0 3.0 %
ILDO[A/B/C](MAX) LDOA, LDOB, LDOC Load Current 200 mA
VLDO[A/B/C](DO) LDOA, LDOB, LDOC Dropout Voltage2VLDO[A/B/C] 3.0V; ILDO = 150mA 75 150 mV
ΔVLDO/
VLDO*ΔVIN
LDOA, LDOB, LDOC Line Regulation VIN = (VLDO[A/B/C] + 1V) to 5V 0.09 %/V
PSRR[A/B/C] LDOA, LDOB, LDOC Power Supply Rejection Ratio ILDO[A/B/C] = 10mA, 1kHz 50 dB
ROUT_(DCHG) LDOA, LDOB, LDOC Auto-Discharge Resistance 20
EN/SET AS2Cwire and Logic Control
VIH
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input High
Threshold Voltage 2.7V VIN 5.5V 1.4 V
VIL
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input Low
Threshold Voltage 2.7V VIN 5.5V 0.4 V
IIN(LKG)
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input Leak-
age Current EN/SET = IN = 5V -1 1 A
tEN/SET(OFF) EN/SET Input OFF Timeout 500 s
tEN/SET(LAT) EN/SET Input Latch Timeout 500 s
tEN/SET(LOW) EN/SET Input LOW Time 0.3 75 s
tENSET(H-MIN) EN/SET Minimum High Time 50 ns
tENSET(H-MAX) EN/SET Maximum High Time 75 s
1. The AAT2861 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion 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.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
6 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
6 2861.2009.02.1.2
www.analogictech.com
Typical Characteristics
Backlight Efficiency vs. Input Voltage
Input Voltage (V)
Efficiency (%)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
30
40
50
60
70
80
90
100
30mA/ch, VF = 3.95V
15mA/ch, VF = 3.5V
4.2mA/ch, VF = 3.4V
Flash Efficiency vs. Input Voltage
Input Voltage (V)
Efficiency (%)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
30
40
50
60
70
80
90
100
320mA/ch, VF = 3.25V
160mA/ch, VF = 3.15V
Backlight Current Matching vs. Temperature
(VIN = 3.6V; 20mA/ch)
Temperature (°C)
Backlight Output Current (mA)
-40 -15 10 35 60 85
16
17
18
19
20
21
22
Channel 1 - Channel 6/7
Charge Pump Output Turn On Characteristic
(VIN = 3.6V; 0mA/ch; COUT = 2.2µF)
Time (50µs/div)
VEN/SET (top) (V)
Output Voltage (bottom) (V)
0.0
2.0
4.0
0.0
1.0
2.0
3.0
4.0
Turn On to 1X Mode Flash
(VIN = 4.2V; 300mA/ch)
Time (50µs/div)
VFL_EN
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VFLX
(2V/div) 0
2
4
0
200
400
600
0
2
4
Turn On to 1.5X Mode Flash
(VIN = 3.6V; 300mA/ch)
Time (50µs/div)
VFL_EN
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VFLX
(2V/div) 0
2
4
0
200
400
600
0
2
4
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 7
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 7
www.analogictech.com
Typical Characteristics
Turn On to 2X Mode Flash
(VIN = 2.8V; 300mA/ch)
Time (50µs/div)
VFL_EN
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VFLX
(2V/div) 0
2
4
0
200
400
600
0
2
4
Turn On to 1X Mode Backlight
(VIN = 3.6V; 20mA/ch)
Time (200µs/div)
VEN/SET
(2V/div)
VOUT
(2V/div)
IIN
(100mA/div)
VSINK
(2V/div)
0V
0V
0A
Turn On to 1.5X Mode Backlight
(VIN = 3.2V; 20mA/ch)
Time (200µs/div)
VEN/SET
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VSINK
(2V/div) 0V
0V
0
A
Turn On to 2X Mode Backlight
(VIN = 3.0V; 20mA/ch)
Time (200µs/div)
VEN/SET
(2V/div)
VOUT
(2V/div)
IIN
(200mA/div)
VSINK
(2V/div)
0V
0V
0A
Turn Off from 1.5X Mode Backlight
(VIN = 3.2V; 20mA/ch)
Time (200µs/div)
VEN/SET
(2V/div)
VDIODE
(2V/div)
IIN
(200mA/div)
Operating Characteristic
(VIN = 3.2V; 20mA/ch Backlight; 1.5x Mode; COUT = 2.2µF)
Time (500ns/div)
Input Voltage (AC coupled)
(top) (mV)
Charge Pump
Out
put Voltage
(AC coupled) (bottom) (mV)
0
10
20
-50
0
50
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
8 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
8 2861.2009.02.1.2
www.analogictech.com
Typical Characteristics
Operating Characteristic
(VIN = 3.0V; 20mA/ch Backlight; 2X Mode; COUT = 2.2µF)
Time (500ns/div)
Input Voltage (AC coupled)
(top) (mV)
Charge Pump
Out
put Voltage
(AC coupled) (bottom) (mV)
0
10
20
-20
-10
0
10
20
LDO A/B/C Load Regulation
(VIN = 3.6V)
Load Current (mA)
LDO Output Voltage Deviatoin (%)
0.1 1 10 100 1000
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
VOUT = 1.8V
VOUT = 3.0V
LDO A/B/C Output Voltage vs. Temperature
(VIN = 3.6V; ILDO = 0mA)
Temperature (°C)
LDO Output Voltage Deviatoin (%)
-40 -15 10 35 60 85
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
VOUT = 1.8V
VOUT = 3.3V
LDO A/B/C Load Transient Response
(
ILDO =
10mA to 200mA;
VIN =
3.6V;
VLDO =
1.8V;
CLDO =
2.2µF)
Time (20µs/div)
LDO Output Current
(top) (mA)
LDO Output Voltage
(bottom) (V)
-500
-400
-300
-200
-100
0
100
200
1.60
1.70
1.80
1.90
2.00
LDO A/B/C Line Transient Response
(VIN = 3.6V to 4.2V; ILDO = 10mA; VOUT = 1.8V; CLDO = 2.2µF)
Time (1ms/div)
Input Voltage
(top) (V)
LDO Output Voltage
(bottom) (V)
3.6
4.0
4.4
1.78
1.79
1.80
1.81
1.82
LDO A/B/C Turn On Characteristic
(VLDO = 1.8V; VIN = 3.6V; CLDO = 2.2µF)
Time (20µs/div)
VENLDOX (top) (V)
LDO Output (bottom) (V)
0.0
2.0
4.0
0.0
0.5
1.0
1.5
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 9
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 9
www.analogictech.com
Typical Characteristics
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C
High Threshold Voltage vs. Input Voltage
Input Voltage (V)
VEN/SET(H), VFL_EN(H),
VEN_LDOA(H), VEN_LDOB/C(H) (V)
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
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
-40°C
25°C
85°C
EN/SET, FL_EN, EN_LDOA, EN_LDOB/C
Low Threshold Voltage vs. Input Voltage
Input Voltage (V)
VEN/SET(L), VFL_EN(L),
VEN_LDOA(L), VEN_LDOB/C(L) (V)
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
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
-40°C
25°C
85°C
EN/SET Input Latch Timeout vs. Input Voltage
Input Voltage (V)
TLAT (µs)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
100
150
200
250
300
350
400
-40°C
25°C
85°C
EN/SET Input Off Timeout vs. Input Voltage
Input Voltage (V)
TOFF (µs)
2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
100
150
200
250
300
350
400
450
500
-40°C
25°C
85°C
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
10 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
10 2861.2009.02.1.2
www.analogictech.com
Functional Block Diagrams
AAT2861IMK-1-T1
BL5
C1-
C1+
C2-
C2+
IN
LDOA
OUT
BL1
BL2
BL3
BL4
BL6
BL7
AGND
EN_LDOA
LDOB
LDOC
IN
EN_LDOB/C
EN/SET
FL_EN
PGND
REF
8
FL1
5
5
4
1x/1.5x/2x
Tri-mode
Charge Pump
Control
Logic
Main
Backlight
Current
Control
Sub
Backlight
Current
Control
Flash
Control
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 11
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AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 11
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AAT2861IMK-2-T1
BL5
1x/1.5x/2x
Tri-mode
Charge Pump
C1-
C1+
C2-
C2+
IN
LDO
A
OUT
BL1
BL2
BL3
BL4
BL6
Control
Logic
FL2
AGND
EN_LDOA
LDOB
LDO
C
IN
EN_LDOB/C
EN/SET
FL_EN
PGND
REF
8
FL1
Flash
Control
Sub
Backlight
Current
Control
Main
Backlight
Current
Control
5
5
4
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
12 2861.2009.02.1.2
www.analogictech.com
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
12 2861.2009.02.1.2
www.analogictech.com
AAT2861IMK-3-T1
BL5
1x/1.5x/2x
Tri-mode
Charge Pump
C1-
C1+
C2-
C2+
IN
LDOA
OUT
BL1
BL2
BL3
BL4
BL6
Control
Logic
BL7
AGND
EN_LDOA
LDOB
LDOC
IN
EN_LDOB/C
EN/SET
FL_EN
PGND
REF
8
FL1
Flash
Control
Sub
Backlight
Current
Control
Main
Backlight
Current
Control
5
5
4
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 13
www.analogictech.com
Functional Description
The AAT2861 is a highly integrated backlight and photo-
flash 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 auto-
matically 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 con-
tinuously 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.
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-
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 pro-
grammed 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.
LDO Regulators
The AAT2861 includes three low dropout (LDO) linear
regulators. These regulators are powered from the bat-
tery 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.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
14 2861.2009.02.1.2
www.analogictech.com
Address Data
1
EN/SET
217 18
Address
Data Reg 1
Data Reg 2
12 . . . n <= 16
01
0
0
n
T
HI
T
LO
T
LAT
T
LAT
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 identi-
fied by 17 rising edges, Address 1 by 18 rising edges,
Address 2 by 19 rising edges, etc. Data is set to any num-
ber 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 pro-
grammed 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.
AS2Cwire Serial Interface Programming
The AAT2861’s AS2Cwire programmable Address regis-
ters 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 dis-
able each backlight or flash channel.
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 cur-
rent 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” set-
ting 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.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 15
www.analogictech.com
Data Sub
Fade On Main
Fade On Sub
Channel Main
Channel
1* No* No* Off* Off*
2 No No Off On
3 No No On Off
4NoNoOnOn
5 No Yes Off Off
6 No Yes Off On
7 No Yes On Off
8 No Yes On On
9 Yes No Off Off
10 Yes No Off On
11 Yes No On Off
12 Yes No On On
13 Yes Yes Off Off
14 Yes Yes Off On
15 Yes Yes On Off
16 Yes Yes On On
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
current threshold (set by Address 1) at which point the
BL channels will be turned off. The default fade-out cur-
rent level is 500A, but can be changed to 1mA, 2mA or
3mA using the data codes listed in Table 3.
Data Fade Out Current Level (mA)
1* 0.50*
2 1.0
3 2.0
4 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 back-
light channels current to one of 32 levels according to
Table 5 below.
*Denotes the default (power-on-reset) value
Address EN/SET
Rising Edges Function D3 D2 D1 D0
0 17 Backlight Main/Sub ON/OFF and Fade Enable FADE_SUB FADE_MAIN SUB_ON MAIN_ON
1 18 Backlight Fade Control X X FLOOR[1] FLOOR[0]
2 19 Backlight Current Main, LSB's BLM[3] BLM[2] BLM[1] BLM[0]
3 20 Backlight Current Main, MSB Reserved X MEQS BLM[4]
4 21 Backlight Current Sub, LSB's BLS[3] BLS[2] BLS[1] BLS[0]
5 22 Backlight Current Sub, MSB X X X BLS[4]
6 23 LDO Disable Control X OFF_LDOC OFF_LDOB OFF_LDOA
7 24 LDO A Output Voltage Control LDOA[3] LDOA[2] LDOA[1] LDOA[0]
8 25 LDO B Output Voltage Control LDOB[3] LDOB[2] LDOB[1] LDOB[0]
9 26 LDO C Output Voltage Control LDOC[3] LDOC[2] LDOC[1] LDOC[0]
10 27 Flash Current F_HI[3] F_HI[2] F_HI[1] F_HI[0]
11 28 Flash Timer Control X X F_TIME[1] F_TIME[0]
12 29 LED Channel Disable Control (BL1 – BL4) OFF_BL4 OFF_ BL3 OFF_ BL2 OFF_ BL1
13 30 LED Channel Disable Control (BL5, BL6,
BL7/FL2, FL1) OFF_FL1 OFF_BL7/FL2 OFF_BL6 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”).
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
16 2861.2009.02.1.2
www.analogictech.com
Main Equals Sub OFF (MEQS=0) Main Equals Sub ON (MEQS=1)
Address Data Address Data Main Current Address Data Address Data Main Current
3121 31 3321 31
3122 30 3322 30
3123 29 3323 29
3124 28 3324 28
3125 27 3325 27
3126 26 3326 26
3127 25 3327 25
3128 24 3328 24
3129 23 3329 23
3 1 2 10 22 3 3 2 10 22
3 1 2 11 21 3 3 2 11 21
3 1* 2 12* 20* 3 3 2 12 20
3 1 2 13 19 3 3 2 13 19
3 1 2 14 18 3 3 2 14 18
3 1 2 15 17 3 3 2 15 17
3 1 2 16 16 3 3 2 16 16
3221 15 3421 15
3222 14 3422 14
3223 13 3423 13
3224 12 3424 12
3225 11 3425 11
3226 10 3426 10
3227 9 3427 9
3228 8 3428 8
3229 7 3429 7
32210 6 34210 6
32211 5 34211 5
32212 4 34212 4
32213 3 34213 3
32214 2 34214 2
32215 1 34215 1
3 2 2 16 0.5 3 4 2 16 0.5
Table 4: Backlight Main Current Control (Addresses 2 and 3).
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 17
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Sub Backlight
Address Data Address Data Sub Current
5141 31
514
2 30
5143 29
5144 28
5145 27
5146 26
5147 25
5148 24
5149 23
51410 22
51411 21
5 1* 4 12* 20*
51413 19
51414 18
51415 17
51416 16
5241 15
5242 14
5243 13
5244 12
5245 11
5246 10
5247 9
5248 8
5249 7
52410 6
52411 5
52412 4
52413 3
52414 2
52415 1
5 2 4 16 0.5
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.
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 set-
tings of the Sub Channel are ignored. All backlight chan-
nels 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.
Part Number
Main Equals Sub (IMAIN = ISUB)
Yes (Default) No
AAT2861-1 7M+0S+1FL 4M+3S+1FL
AAT2861-2 6M+0S+2FL 4M+2S+2FL
AAT2861-3 7M+0S+1FL 5M+2S+1FL
Table 6: Main and Sub Channel Configurations.
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 com-
mand 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 volt-
ages for LDOA, LDOB, and LDOC to one of 16 levels. The
available LDO output voltages are shown in Table 8.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
18 2861.2009.02.1.2
www.analogictech.com
Data LDO C LDO B LDO A
1* Controlled by
EN_LDOB/C*
Controlled by
EN_LDOB/C*
Controlled by
EN_LDOA*
2Controlled by
EN_LDOB/C
Controlled by
EN_LDOB/C OFF
3Controlled by
EN_LDOB/C OFF Controlled by
EN_LDOA
4Controlled by
EN_LDOB/C OFF OFF
5 OFF Controlled by
EN_LDOB/C
Controlled by
EN_LDOA
6 OFF Controlled by
EN_LDOB/C OFF
7 OFF OFF Controlled by
EN_LDOA
8 OFF OFF OFF
Table 7: LDO Disable Control (Address 6).
Data VLDOA (V) VLDOB (V) VLDOC (V)
1 1.2 1.2 1.2
2 1.3 1.3 1.3
3 1.5 1.5 1.5
4 1.6 1.6 1.6
5* 1.8* 1.8* 1.8*
6222
7 2.2 2.2 2.2
8 2.5 2.5 2.5
9 2.6 2.6 2.6
10 2.7 2.7 2.7
11 2.8 2.8 2.8
12 2.9 2.9 2.9
13333
14 3.1 3.1 3.1
15 3.2 3.2 3.2
16 3.3 3.3 3.3
Table 8: LDO X Output Voltage
(Addresses 7, 8, and 9).
Fast turn-off response time is achieved by an active out-
put pull-down circuit, which is enabled when the LDO
regulator is disabled.
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-on-
reset value in Address 10 is set to data code 13.
Data
Flash Current (mA) per Output
AAT2861-1 or -3 AAT2861-2
1 600 300
2560 280
3 520 260
4 480 240
5 440 220
6 400 200
7 360 180
8 320 160
9 280 140
10 240 120
11 200 100
12 160 80
13* 120* 60*
14 80 40
15 40 20
16 OFF OFF
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.
*Denotes default (power-on-reset) value.
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
2861.2009.02.1.2 19
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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 auto-
matically disabled and the flash channels will remain on
as long as the FL_EN pin remains active. Extended dura-
tion 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 Flash Time (sec)
1* 2*
21
3 0.5
4 Always ON
Table 10: Flash Safety Timer (Address 11).
LED Channel Disable Control
(Address 12 and 13)
Addresses 12 and 13 allow for additional programming
flexibility by allowing each LED channel to be indepen-
dently 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 con-
trols 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.)
*Denotes default (power-on-reset) value.
Data BL4 BL3 BL2 BL1
1* Conditionally ON* Conditionally ON* Conditionally ON* Conditionally ON*
2 Conditionally ON Conditionally ON Conditionally ON OFF
3 Conditionally ON Conditionally ON OFF Conditionally ON
4 Conditionally ON Conditionally ON OFF OFF
5 Conditionally ON OFF Conditionally ON Conditionally ON
6 Conditionally ON OFF Conditionally ON OFF
7 Conditionally ON OFF OFF Conditionally ON
8 Conditionally ON OFF OFF OFF
9 OFF Conditionally ON Conditionally ON Conditionally ON
10 OFF Conditionally ON Conditionally ON OFF
11 OFF Conditionally ON OFF Conditionally ON
12 OFF Conditionally ON OFF OFF
13 OFF OFF Conditionally ON Conditionally ON
14 OFF OFF Conditionally ON OFF
15 OFF OFF OFF Conditionally ON
16 OFF OFF OFF OFF
Table 11: LED Channel Individual Disable Control, BL1-BL4 (Address 12).
AAT2861
Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
ChargePumpTM
PRODUCT DATASHEET
20 2861.2009.02.1.2
www.analogictech.com
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 speci-
fications ranging from 2.0V to 4.7V. LED applications
may include mixed arrangements for display backlight-
ing, 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 com-
bined to obtain a higher LED drive current without com-
plication.
Device Switching Noise Performance
The AAT2861 operates at a fixed frequency of approxi-
mately 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 induc-
tor-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 sec-
tions 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.
Data FL1 BL7/FL2 BL6 BL5
1* Conditionally ON* Conditionally ON * Conditionally ON* Conditionally ON*
2 Conditionally ON Conditionally ON Conditionally ON OFF
3 Conditionally ON Conditionally ON OFF Conditionally ON
4 Conditionally ON Conditionally ON OFF OFF
5 Conditionally ON OFF Conditionally ON Conditionally ON
6 Conditionally ON OFF Conditionally ON OFF
7 Conditionally ON OFF OFF Conditionally ON
8 Conditionally ON OFF OFF OFF
9 OFF Conditionally ON Conditionally ON Conditionally ON
10 OFF Conditionally ON Conditionally ON OFF
11 OFF Conditionally ON OFF Conditionally ON
12 OFF Conditionally ON OFF OFF
13 OFF OFF Conditionally ON Conditionally ON
14 OFF OFF Conditionally ON OFF
15 OFF OFF OFF Conditionally ON
16 OFF OFF OFF OFF
Table 12: LED Channel Individual Disable Control, BL5, BL6, BL7/FL2, FL1 (Address 13).
*Denotes default (power-on-reset) value.
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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 for-
ward voltage levels can differ, yet the output drive cur-
rent 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 volt-
age 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 com-
bination 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 dif-
ferent 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:
η = =
PLEDs
PIN
VLED1 · ILED1 + ... + VLEDX · ILEDX
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:
η = =
PLEDs
PIN
X · VLEDX · ILEDX
VIN · IIN
X = 1, 2, 3, ..., 6 or 7 and IIN = X · ILEDX
η =
VLEDX
VIN
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 sim-
ply 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:
η = =
PLEDs
PIN
VLED1 · ILED1 + ... + VLEDX · ILEDX
VIN · IIN
η = ; X = 1, 2, 3, ..., 6 or 7 and IIN = 1.5(X · ILEDX)
η =
X · VLEDX · ILEDX
VIN · IIN
VLEDX
1.5VIN
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 esti-
mated ideal efficiency () for the AAT2861 in 2x mode is
as follows:
η = =
PLEDs
PIN
VLED1 · ILED1 + ... + VLEDX · ILEDX
VIN · IIN
η = ; X = 1, 2, 3, ..., 6 or 7 and IIN = 2(X · ILEDX)
η =
X · VLEDX · ILEDX
VIN · IIN
VLEDX
2VIN
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 con-
sumption, 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.
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
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Manufacturer Part Number Value Voltage Temp. Co. Case
AVX 0603ZD105K 1F10X5R 0603
0603ZD225K 2.2F10
TDK
C1608X5R1E105K 1F25
X5R 0603C1608X5R1C225K 2.2F16
C1608X5R1A475K 4.7F10
Murata GRM188R61C105K 1F16X5R 0603
GRM188R61A225K 2.2F10
Taiyo Yuden LMK107BJ475KA 4.7F 10 X5R 0603
Table 13: Surface Mount Capacitors.
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 counter-
parts. 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 con-
nection damage.
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 connec-
tions, size or area, material composition and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms 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 tem-
perature. 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.
These larger size capacitors can improve circuit transient
response when compared to an equal value capacitor in
a smaller package size.
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 pad-
dle. 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 prac-
tice to connect the GND pins to the exposed paddle area
with traces as shown in the example.
The flying capacitors C1 and C2 should be connected
close to the IC. Trace length should be kept short to
minimize path resistance and potential coupling. The
input and output capacitors should also be placed as
close to the chip as possible.
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Button(s) Pushed Description
SW1
[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.
SW2
[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 se-
quence for Sub channels. When these sequences are fi nished the program will restart fade out sequence
for all Main and Sub channels.
SW3
[Push/Release once] Flash channels are programmed with maximum current and timer. With every sub-
sequent push/release the fl ash current is decreased according to Table 9. The FLASH button needs to be
pressed down simultaneously.
FLASH This button is connected directly to FL_EN pin. Press and hold for the fl ash to be enabled.
Table 14: AAT2861 Evaluation Board User Interface.
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 combi-
nations. Table 14 indicates the function of each button or
button combination.
To power-on the evaluation board, connect a power sup-
ply or battery to the DC- and DC+ terminals. A red LED
indicates that power is applied.
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 evalua-
tion board. For adequate performance, be sure to con-
nect the load between LDOA/LDOB/LDOC and DC- as
opposed to some other GND in the system.
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Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
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C3
2.2µF
C6
2.2µF
C5
4.7µF
C7
2.2µF
R1
1K
R2
1K
R3
1K
D1D2
D3
D4
OUT
DC+
VDD
1
GP5
2
GP4
3
GP3
4GP2 5
GP1 6
GP0 7
VSS 8
PIC12F675
U3
C9
1µF
R6
330
LED7
RED
14 23
5SW2
14 23
5SW3
14 23
5
FLASH
DC+
DC+
DF2
DF1
14 23
5SW1
OUT
1
C2+
2
EN/SET
3
FL_EN
4
EN_LDOA
5
EN_LDOB/C
6
AGND
7BL2
BL1LDOALDOBINLDOC
13
12111089
BL3 14
BL4 15
BL5 16
BL6 17
BL7/FL2 18
FL1 19
20
2122
2324
U1
AAT2861-X
D5
D6
D7
DC+
IN
R5
0
R4
10K
R7
10K
C8
2.2µF
C2
1.0µF
C1
1.0µF
C4
4.7µF
C1+ IN PGNDC1- C2-
Figure 2: AAT2861 Evaluation Board Schematic.
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Figure 3: AAT2861 Evaluation Board Top Side Layout.
Figure 4: AAT2861 Evaluation Board Bottom Side Layout.
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Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit
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Component Part# Description Manufacturer
U1 AAT2861IMK-x-T1 High Eff. 1X/1.5X/2X CP for White LED, Triple LDO AnalogicTech
U2 PIC12F675 8-bit CMOS, FLASH MCU; 8-pin PDIP Microchip
D1-D7 LW M673 Mini TOPLED White LED; SMT OSRAM
DF1, DF2 LXCL PWF1 Mini TOPLED Flash LED; SMT Lumileds, Philips
C1, C2 GRM18x 1.0F, 10V, X5R, 0603, Ceramic Murata
C3, C6, C7, C8 GRM18x 2.2F, 10V, X5R, 0603, Ceramic Murata
C4, C5 GRM18x 4.7F, 10V, X5R, 0603, Ceramic Murata
R1-R3 Chip Resistor 1K, 5%, 1/4W; 0603 Vishay
R4 Chip Resistor 10K, 5%, 1/4W; 0603 Vishay
R6 Chip Resistor 330, 5%, 1/4W; 1206 Vishay
R5 Chip Resistor 0, 5%, 1/4W; 1206 Rohm
LED7 CMD15-21SRC/TR8 Red LED; 1206 Chicago Miniature Lamp
SW1-SW3, FLASH PTS645TL50 Switch Tact, SPST, 5mm ITT Industries
Table 15: AAT2681 Evaluation Board Bill of Materials (BOM),
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Phone (408) 737-4600
Fax (408) 737-4611
© 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 specifi cations or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
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Ordering Information
Package Marking1Part Number (Tape and Reel)2
TQFN34-24 4KXYY AAT2861IMK-1-T1
TQFN34-24 4LXYY AAT2861IMK-2-T1
TQFN34-24 4XXYY 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
4.000
±
0.050
Top View Bottom View
Side View
Detail “A”
1.700
±
0.050
Detail “A”
R(5x)
Index Area
0.210
±
0.040
2.700
±
0.050
0 + 0.10
- 0.00
0.750
±
0.050
0.203 REF
0.400 BSC
0.400
±
0.050
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.
