AAT2866 - Skyworks Solutions, Inc.

DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
General Description
Features
The AAT2866 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 and multiple backlight
and flash LED configurations are available. The backlight
LED channel outputs are programmable up to 31mA and
the total flash LED output current can be programmed
up to 600mA.
• Input Voltage Range: 2.7V to 5.5V
• AS2Cwire Serial Interface
• Tri-Mode Charge Pump
▪ Drives up to Eight LEDs
• Programmable Backlight Current by:
▪ AS2Cwire Interface
•31mA Maximum Current per Channel
•32 Linear Current Settings
•Independent Main/Sub Settings
▪ PWM Control
•All Channels BL1-BL6 (default)
•Main Backlight BL1-BL4 (optional)
•All Channels BL1-BL7 (AAT2866-3)
•60Hz to 100kHz
▪ Programmable Flash Current
•600mA Total Flash Current
•16 Linear Current Settings
•2 Channel Configuration
• 1MHz Switching Frequency
• Automatic Soft Start
• Three Linear Regulators
▪ 300mA Output Current
▪ 150mV Dropout
▪ Programmable Control 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
Skyworks' AS2Cwire™ 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
separate flash enable and programmable safety timer 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. As an alternative, the main backlight
LED's output current can be controlled via pulse width
modulation (PWM).
The AAT2866 also offers three high-performance lownoise MicroPower™ low dropout (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 80µA
making the AAT2866 ideal for battery-operated applications.
The AAT2866 is available in a Pb-free, space-saving
TQFN34-24 package and operates over the -40°C to
+85°C ambient temperature range.
Applications
• Camera Enabled Mobile Devices
• Digital Still Cameras
• Multimedia Mobile Phones
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
1
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Typical Application
CF1
1µF
C1+
CF2
1µF
C1- C2+
IN
VBAT
3.6V
CIN
2.2µF
PWMM
C2OUT
VOUT
COUT
2.2µF
AAT2866
IN
PWMM
BL1
BL2
BL3
BL4
EN/SET
EN/SET
BL5
BL6
BL7/FL2
FL_EN
FL_EN
FL1
LDOA
EN_LDOA/B/C
EN_LDOA/B/C
LDOB
2
COUTA
2.2µF
VLDOB
at 300mA
COUTB
2.2µF
LDOC
AGND
VLDOA
at 300mA
PGND
VLDOC
at 300mA
COUTC
2.2µF
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Pin Descriptions
Pin #
Symbol
Function
1
OUT
O
2
C2+
I
3
EN/SET
I
4
FL_EN
I
5
PWMM
I
6
EN_LDOA/B/C
I
7
AGND
GND
8
LDOC
O
9
IN
I
10
LDOB
O
11
LDOA
O
12
BL1
O
13
BL2
O
14
BL3
O
15
BL4
O
16
BL5
O
17
BL6
O
18
BL7/FL2
O
19
FL1
O
20
21
22
PGND
C2C1-
GND
I
I
23
IN
I
24
C1+
I
EP
GND
Description
Charge-pump output. OUT is the output of the charge pump and supplies current to the
backlight and flash LEDs. Connect the backlight and flash LED anodes to OUT. Bypass OUT
to PGND with a 2.2μF or larger ceramic capacitor as close to the AAT2866 as possible.
Positive terminal of charge pump capacitor 2. Connect the 1μF 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.
PWM input pin. Apply a PWM signal of varying duty cycle to modulate the LED current on
BL1, BL2, BL3, BL4, BL5 & BL6 (Default). PWM frequency can vary up to 100kHz. The LED
current maximum will be set at the default setting if no programming is applied. If not used,
connect PWMM to IN.
LDOA, LDOB and LDOC enable pin. EN_LDOA/B/C enables all LDO regulators A. The EN/SET
pin must also be pulled high for the LDO regulators to be enabled. The EN_LDOA/B/C input
can be overwritten via the AS2Cwire interface to disable either LDOA or LDOB or LDOC.
Analog ground. Connect AGND to PGND at a single point as close to the AAT2866 as possible.
LDOC is the voltage output of LDOC. Bypass LDOC to AGND with a 2.2μF or greater capacitor as close to the AAT2866 as possible.
Input power pin for all three LDOs. Connect Pin 11 to Pin 23 with as short a PCB trace as
practical.
LDOB is the voltage output of LDOB. Bypass LDOB to AGND with a 2.2μF or greater capacitor as close to the AAT2866 as possible.
LDOA is the voltage output of LDOA. Bypass LDOA to AGND with a 2.2μF or larger ceramic
capacitor as close to the AAT2866 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.
AAT2866: 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.
AAT2866-3: 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.
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 AAT2866 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 2.2μF or
larger ceramic capacitor as close to the AAT2866 as possible.
Positive terminal of charge pump capacitor 1. Connect the 1μF charge pump capacitor 1
from C1+ to C1-.
Exposed paddle (bottom) Connect to PGND/AGND as close to the AAT2866 as possible.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
3
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Pin Configuration
TQFN34-24
(Top View)
PGND
C2C1IN
C1+
24
OUT
C2+
EN/SET
FL_EN
PWMM
EN_LDOA/B/C
AGND
23
22
21
20
1
19
2
18
3
17
4
16
5
15
6
14
7
13
8
9
10
11
FL1
BL7/FL2
BL6
BL5
BL4
BL3
BL2
12
BL1
LDOA
LDOB
IN
LDOC
Part Number Description1
Backlight LED Outputs
Part Number
Main
Sub
Flash LED Output
AAT2866IMK-T1
AAT2866IMK-3-T1
6/4
5
0/2
2
2
1
Absolute Maximum Ratings2
TA = 25°C unless otherwise noted.
Symbol
Description
IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6, FL1, BL7/FL2 Voltage to AGND
C1+, C2+ Voltage to AGND
C1-, C2-, LDOA, LDOB, LDOC, EN/SET, FL_EN, EN_LDOA/B/C, PWMM Voltage to AGND
PGND Voltage to AGND
Value
Units
-0.3 to 6.0
-0.3 to VOUT + 0.3
-0.3 to VIN + 0.3
-0.3 to 0.3
V
Thermal Information3, 4
Symbol
ΘJA
PD
TJ
TLEAD
Description
Thermal Resistance
Maximum Power Dissipation
Operating Junction Temperature Range
Maximum Soldering Temperature (at Leads)
Value
Units
50
2
-40 to 150
300
OC/W
W
°C
1. Backlight Main and Sub are configured to be equal by default. Main and Sub can be programmed via AS2Cwire to be 4 Main and 2 Sub . For more information, see the Applications
Information section of this datasheet.
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.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Electrical Characteristics1
VIN = 3.6V; CIN = COUT = 2.2μF; C1 = C2 = 1µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =
25°C.
Symbol
Description
Conditions
VIN
IN Operating Voltage Range
IN Operating Current (1x mode,
Main Channels enabled, IBLX not
included)
IN Operating Current (2x mode,
IIN
Main Channels enabled, IBLX not
included)
IN Operating Current (LDOA,
LDOB and LDOC enabled)
IIN(SHDN)
IN Shutdown Current
Over-Temperature Shutdown
TSD
Threshold
Over-Temperature Shutdown
TSD(HYS)
Hysteresis
Charge Pump Section
VOUT
OUT Output Voltage
IOUT(MAX)
OUT Maximum Output Current
BL1-BL7 Charge Pump Mode
VIN(TH_H, BL)
Transition Hysteresis
FL1-FL2 Charge Pump Mode
VIN(TH_H, FL)
Transition Hysteresis
fOSC
Charge Pump Oscillator Frequency
tCP(SS)
Charge Pump Soft-Start Time
BL1-BL7, FL1, FL2 LED Drivers
IBLx
BL1-BL7 Current Accuracy
IBL_x
BL1-BL7 Current Accuracy
IBL_(10%)
ΔI(BLx)/
IBL(AVG)
VBL_(TH)
BL1-BL7 PWM Current Accuracy
BL1-BL7 Current Matching
2
BL1-BL7 Charge Pump Transition
Threshold
IFL[1]
FL1,FL2 Current Accuracy
IFL[1](DATA13)
FL1, FL2 Current Accuracy
ΔI(FLx)/
IFL(AVG)
FL1-FL2 Current Matching
VFL[1/2](TH)
FL1,FL2 Charge Pump Transition
Threshold
ΔtFL/tFL_SET
Flash Safety Timer Period
Min
Typ
Max
Units
5.5
V
600
µA
5.5
mA
225
µA
1.0
µA
2.7
EN/SET = PWMM = BL1-BL7 = IN, FL_EN =
EN_LDOA/B/C = AGND;
2x Mode; EN/SET= PWMM = IN, FL_EN =
EN_LDOA/B/C = AGND; BL1-BL7 = OPEN;
ADDR=12, DATA=15; ADDR=13, DATA=16
EN/SET = PWMM = EN_LDOA/B/C = IN; FL_EN =
AGND; ADDR = 0; DATA = 6; No Load
EN/SET, FL_EN, EN_LDOA/B/C, PWMM = AGND
VIN = 3.0V, VOUT = 4.0V
EN/SET = IN; VIN – VF = 1V; ADDR=3, DATA=2;
ADDR=2, DATA=12
EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR=10,
DATA=1
TA = 25°C
TA = 25°C
EN/SET = IN; VIN – VF = 1V; ADDR=3, DATA=3;
ADDR=2, DATA=12
EN/SET = IN; VIN – VF = 1V; ADDR=3, DATA=4;
ADDR=2, DATA=14
DC=10%; fPWM=10kHz; VIN-VF=1.5V
EN/SET = IN; VIN – VF = 1V; ADDR=3, DATA=3;
ADDR=2, DATA=12
EN/SET = IN; VIN – VF = 1V; ADDR=3, DATA=3;
ADDR=2, DATA=12
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
140
°C
15
°C
5.2
800
V
mA
0.3
V
1
V
1
100
MHz
µs
18
20
22
mA
1.6
2
2.4
mA
2.5
mA
3
%
0.2
V
270
300
330
mA
54
60
66
mA
1.5
5
%
0.45
V
2
2.5
s
1. The AAT2866 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
2. Current matching is defined as the deviation of any sink current from the average of all active channels.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
5
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Electrical Characteristics1
VIN = 3.6V; CIN = COUT = 2.2μF; C1 = C2 = 1µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =
25°C.
Symbol
Description
Linear Regulators
ΔVLDO[A/B/C]/
LDOA, LDOB, LDOC Output Voltage
VLDO[A/B/C]
Tolerance
LDOA, LDOB, LDOC Maximum Load
ILDO[A/B/C](MAX)
Current
VLDO[A/B/C](DO)
LDOA, LDOB, LDOC Dropout Voltage2
∆VLDO/
LDOA, LDOB, LDOC Line Regulation
VLDO*∆VIN
LDOA, LDOB, LDOC Power Supply
PSRR[A/B/C]
Rejection Ratio
LDOA, LDOB, LDOC Auto-Discharge
RLDO_(DCHG)
Resistance
AS2Cwire and Logic Control
EN/SET, FL_EN, PWMM, EN_LDOA/
VIH
B/C Input High Threshold Voltage
EN/SET, FL_EN, PWMM, EN_LDOA/
VIL
B/C Input Low Threshold Voltage
IIN(LKG)
EN Input Leakage Current
tEN/SET(OFF)
EN/SET Input OFF Timeout
tEN/SET(LAT)
EN/SET Input Latch Timeout
tEN/SET(LOW)
EN/SET Input LOW Time
tENSET(H-MIN)
EN/SET Minimum High Time
tENSET(H-MAX)
EN/SET Maximum High Time
Conditions
Min
ILDO = 1mA to 200mA; TA = 25°C
ILDO = 1mA to 200mA; TA = -40°C to +85°C
-1.5
-3.0
Typ
Max
Units
1.5
3.0
%
200
VLDO[A/B/C] ≥ 3.0V; ILDO = 150mA
75
VIN = (VLDO[A/B/C] + 1V) to 5V
ILDO[A/B/C] =10mA, 1kHz
2.7V ≤ VIN ≤ 5.5V
mA
mV
0.09
%/V
50
dB
1.5
kΩ
1.4
V
2.7V ≤ VIN ≤ 5.5V
EN/SET = PWMM = EN_LDOA/B/C = IN = 5V
150
-1
0.3
0.4
V
1
500
500
75
μA
µs
µs
µs
ns
µs
50
75
1. The AAT2866 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
2.VDO[A/B/C] is defined as VIN – LDO[A/B/C] when LDO[A/B/C] is 98% of nominal.
6
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Typical Characteristics
Flash Efficiency vs. Input Voltage
100
100
90
90
80
80
Efficiency (%)
Efficiency (%)
Backlight Efficiency vs. Input Voltage
70
60
50
30mA/ch, VF = 3.95V
15mA/ch, VF = 3.5V
4.2mA/ch, VF = 3.4V
40
30
2.7
3.1
3.5
60
50
320mA/ch, VF = 3.25V
160mA/ch, VF = 3.15V
40
3.9
4.3
4.7
5.1
30
2.7
5.5
Input Voltage (V)
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Backlight Current Matching vs. Temperature
Charge Pump Output Turn On Characteristic
(VIN = 3.6V; 20mA/ch)
(VIN = 3.6V; 0mA/ch; COUT = 2.2µF)
22
4.0
VEN/SET (top) (V)
21
20
19
Channel 1 - Channel 6/7
18
2.0
4.0
0.0
3.0
2.0
1.0
17
0.0
16
-40
-15
10
35
60
85
Temperature (°C)
Time (50µs/div)
Turn On to 1x Mode Flash
Turn On to 1.5x Mode Flash
(VIN = 4.2V; 300mA/ch)
VOUT
(2V/div)
VFLX
(2V/div)
(VIN = 3.6V; 300mA/ch)
4
VFL_EN
(2V/div)
4
VFL_EN
(2V/div)
2
0
VOUT
(2V/div)
VFLX
(2V/div)
4
2
600
0
2
0
4
2
0
600
400
IIN
(200mA/div)
400
IIN
(200mA/div)
200
0
Time (50µs/div)
Output Voltage (bottom) (V)
Backlight Output Current (mA)
70
200
0
Time (50µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
7
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Typical Characteristics
Turn On to 2x Mode Flash
Turn On to 1x Mode Backlight
(VIN = 2.8V; 300mA/ch)
4
VFL_EN
(2V/div)
VOUT
(2V/div)
VFLX
(2V/div)
(VIN = 4.2V; 20mA/ch)
2
0
4
2
0
600
400
IIN
(200mA/div)
200
0
Time (50µs/div)
EN/SET
(2V/div)
0V
VCP
(2V/div)
0V
VBLx
(2V/div)
0V
IIN
(100mA/div)
0A
Time (100µs/div)
Turn On to 1.5x Mode Backlight
Turn On to 2x Mode Backlight
(VIN = 3.2V; 20mA/ch)
EN/SET
(2V/div)
VCP
(2V/div)
VBLx
(2V/div)
IIN
(100mA/div)
(VIN = 2.7V; 20mA/ch)
EN/SET
(2V/div)
0V
VCP
(2V/div)
VBLx
(2V/div)
0V
0V
0V
0V
IIN
(200mA/div)
0A
Time (100µs/div)
Operating Characteristic
(VIN = 3.2V; 20mA/ch Backlight; 1.5x Mode; COUT = 2.2µF)
VEN/SET
(2V/div)
VDIODE
(2V/div)
IIN
(200mA/div)
20
10
0
50
0
Charge Pump Output Voltage
(AC coupled) (bottom) (mV)
Input Voltage (AC coupled)
(top) (mV)
(VIN = 3.2V; 20mA/ch)
Time (200µs/div)
0A
Time (200µs/div)
Turn Off from 1.5x Mode Backlight
8
0V
-50
Time (500ns/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202262A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • August 10, 2012
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Typical Characteristics
Operating Characteristic
LDO Load Regulation vs. Output Current
10
0
20
10
0
-10
-20
Time (500ns/div)
1.8
Output Error (%)
20
(VOUT = 1.2V)
Charge Pump Output Voltage
(AC coupled) (bottom) (mV)
Input Voltage (AC coupled)
(top) (mV)
(VIN = 3.0V; 20mA/ch Backlight; 2x Mode; COUT = 2.2µF)
-1.0
60
85
Temperature (°C)
0
-100
2.00
-200
1.90
-300
1.80
-400
1.70
-500
1.60
Time (20µs/div)
LDO A/B/C Line Transient Response
LDO A/B/C Turn On Characteristic
1.80
1.79
VENLDOX (top) (V)
Input Voltage
(top) (V)
1.81
4.0
2.0
0.0
1.5
1.0
0.5
0.0
1.78
Time (1ms/div)
LDO Output (bottom) (V)
1.82
(VLDO = 1.8V; VIN = 3.6V; CLDO = 2.2µF)
LDO Output Voltage
(bottom) (V)
3.6
1000
100
(VIN = 3.6V to 4.2V; ILDO = 10mA; VOUT = 1.8V; CLDO = 2.2µF)
4.0
100
200
4.4
10
Load Current (mA)
LDO Output Current
(top) (mA)
LDO Output Voltage Deviatoin (%)
-0.5
35
1
LDO Output Voltage
(bottom) (V)
0.0
10
-1.2
LDO A/B/C Load Transient Response
0.5
-15
-0.6
(ILDO = 10mA to 200mA; VIN = 3.6V; VLDO = 1.8V; CLDO = 2.2µF)
VOUT = 1.8V
VOUT = 3.3V
-1.5
-40
0.0
(VIN = 3.6V; ILDO = 0mA)
1.0
0.6
-1.8
0.1
LDO A/B/C Output Voltage vs. Temperature
1.5
85°C
25°C
-40°C
1.2
Time (20µs/div)
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9
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Typical Characteristics
EN/SET, FL_EN, PWMM, EN_LDOA/B/C
High Threshold Voltage vs. Input Voltage
EN/SET, FL_EN, PWMM, EN_LDOA/B/C
Low Threshold Voltage vs. Input Voltage
1.2
VEN/SET(L), VFL_EN(L),
VPWMM(L), VEN_LDOA/B/C(L) (V)
VEN/SET(H), VFL_EN(H),
VPWMM(H), VEN_LDOA/B/C(H) (V)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
-40°C
25°C
85°C
0.6
0.5
0.8
0.7
0.6
0.5
-40°C
25°C
85°C
0.4
0.3
Input Voltage (V)
EN/SET Input Off Timeout vs. Input Voltage
400
500
450
350
400
300
TOFF (µs)
TLAT (µs)
0.9
EN/SET Input Latch Timeout vs. Input Voltage
250
200
-40°C
25°C
85°C
150
100
2.7
1.0
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
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
Input Voltage (V)
1.1
3.1
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
350
300
250
200
-40°C
25°C
85°C
150
100
2.7
5.5
3.1
3.5
3.9
4.3
4.7
Input Voltage (V)
10
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5.1
5.5
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Functional Block Diagram
IN
IN
C1C1+
C2-
LDOA
1x/1.5x/2x
Tri -mode
Charge Pump
C2+
LDOB
OUT
LDOC
8
REF
BL1
EN/SET
5
FL_EN
EN_LDO A/B/C
Main
Backlight
Current
Control
BL2
BL3
BL4
Control
Logic
5
PWMM
4
PGND
Sub
Backlight
Current
Control
Flash
Control
BL5
BL6
BL7/FL2
FL1
AGND
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11
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Functional Description
The AAT2866 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
get their power from the same input and produce regulated output voltages between 1.2V and 3.3V. Control of
the LEDs and the LDO output voltages are through an
AS2Cwire serial interface for easy programming. In addition, BL1-BL6 (AAT2866) or BL1-BL7 (AAT2866-3) LED
current can be controlled via an external PWM signal.
LED Drivers
The AAT2866 drives six backlight LEDs up to 31mA each
and a total of 600mA flash current through two channels.
The LEDs are driven from a charge pump to insure that
constant current is maintained for all possible LED forward voltages 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 1μF 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 voltages drops below 200mV or the flash
current sink 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 AAT2866 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.
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 approximately 1mA steps while the flash LED current can be set
between 0 to 300mA in 20mA steps for each channel.
12
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 AAT2866 also includes a safety timer that prevents overstress of the flash LEDs. This is important
because many flash LEDs operate for a brief period
beyond their steady-state operating limitations. If the
flash driving hardware and/or software fails to turn 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 including
the flash safety timer. See the “AS2Cwire Serial Interface
Programming” section for more information on setting
the LED currents.
PWM Controlled Dimming
As an alternative to digital dimming via the AS2Cwire
serial interface, the AAT2866 also provides an additional
pin, PWMM, which allows the user to control BL1-BL6
(AAT2866) or BL1-BL7 (AAT2866-3) or the Main BL1-BL4
(AAT2866) or BL1-BL5 (AAT2866-3) (optional, when
MEQS is deactivated) backlight LEDs with a PWM signal.
The Sub backlight channels BL5-BL6 (AAT2866) or BL6BL7 (AAT2866-3) current is set by AS2Cwire interface.
The PWM signal will modulate the LED current set by
AS2Cwire programming or the AAT2866 default current.
In this mode the minimum PWM frequency is 60Hz. PWM
frequencies as high as 100kHz can be used.
LDO Regulators
The AAT2866 family includes three low dropout (LDO)
linear regulators. These regulators are powered from the
battery and produce fixed output voltages 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 pin EN_LDOA/B/C. Additionally, the AS2Cwire
interface allows the LDO regulators to be enabled independently when the EN_LDOA/B/C pin is pulled high.
All LDO regulators require only small 2.2μF ceramic output capacitors for stability. If improved load transient
response is required, larger-valued capacitors can be
used without stability degradation.
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
AS2Cwire Serial Interface Protocol
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-BL6 (AAT2866)
or BL1-BL7 (AAT2866-3) will be enabled according to the
number of data edges applied.
The AAT2866 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.
AS2Cwire latches data or address after the EN/SET input
has been held high for time tLAT (500µs). 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 time-out 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
When EN/SET is held low for a time longer than tOFF
(500µs), the AAT2866 enters shutdown mode and draws
less than 1µA of current from IN. At shutdown, the data
and address registers are reset to 0.
AS2Cwire Serial Interface Programming
The AAT2866’s AS2C programming Address registers are
listed in Table 1. There are 13 active Address registers;
four control the three LDOs, four control the backlight
LED configuration/control, two control the flash current
and timer control, two are used to individually disable
each backlight or flash channel, and one is reserved for
test purposes.
Address
Data
THI
TLO
TLAT
TLAT
EN/SET
1
Address
2
17
18
1
0
2...
n <= 16
1
Data Reg 1
0
Data Reg 2
0
n
Figure 1: AS2Cwire Serial Interface Timing Diagram.
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13
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Address
EN/SET
Rising Edges
Function
D3
D2
D1
D0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Backlight Main/Sub
Reserved
Backlight Current Main, LSBs
Backlight Current Main, MSB
Backlight Current Sub, LSBs
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, FL1, FL2)
Reserved
Reserved
BLM[3]
Reserved
BLS[3]
X
X
LDOA[3]
LDOB[3]
LDOC[3]
F_HI[3]
X
OFF_BL4
OFF_FL1
Reserved
Reserved
BLM[2]
X
BLS[2]
X
OFF_LDOC
LDOA[2]
LDOB[2]
LDOC[2]
F_HI[2]
X
OFF_ BL3
OFF_ FL2
SUB_OFF
Reserved
BLM[1]
MEQS*
BLS[1]
X
OFF_LDOB
LDOA[1]
LDOB[1]
LDOC[1]
F_HI[1]
F_TIME[1]*
OFF_ BL2
OFF_BL6
MAIN_OFF
Reserved
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: AAT2866 Configuration/Control Register Allocation.
Backlight Main and
Sub Control (Address 0)
Backlight Current Control
(Addresses 2 to 5)
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-BL6) is ON after
power-up.
The AAT2866’s AS2Cwire Addresses 2, 3, 4, and 5 control
the backlight LED output current level in each group of
outputs. Address 2 and Address 3 control the Main channel backlight current to one of 32 levels according to
Table 3 below. Address 3 acts as the MSB for the current
levels. Address 4 and Address 5 control the Sub channel
backlight current to one of 32 levels according to Table 4
below.
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 off by immediately writing
data. For example, if Data=3 is written, the main channels will turn off and the sub channels will turn on to the
default value of 20mA.
Data
Sub Channel On
Main Channel On
1*
2
3
4
On*
On
Off
Off
On*
Off
On
Off
Table 2: Backlight Main/Sub Enable (Address 0).
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. 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.
“*” signifies that the data bit has a POR default bit value = 1; “X” signifies “Don’t care.”
14
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Main Equals Sub OFF (MEQS=0)
Main Equals Sub ON (MEQS=1)
Address
Data
Address
Data
Main Current
Address
Data
Address
Data
Main Current
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
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
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
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
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
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
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
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
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
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
Table 3: Backlight Main Current Control (Addresses 2 and 3).
* denotes the register’s default (power-on-reset) value.
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15
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Sub Backlight
Address
Data
Address
Data
Sub Current
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
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
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
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
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
Table 4: Backlight Sub Current Control
(Addresses 4 and 5).
Table 5 shows the Main and Sub Channel Configurations
for the AAT2866. The effect of the “Main Equals Sub”
feature is clearly represented in Table 5.
LDO Output Voltage Control
(Addresses 6 to 9)
Configuring the AAT2866’s three LDO regulators is performed by programming Addresses 6, 7, 8, and 9 over
the AS2C interface. With the EN/SET pin pulled high and
the AAT2866 turned on, LDO A and LDO B and LDO C
can be enabled together using the EN_LDOA/B/C pin.
Additional LDO regulator control can be achieved using
Address 6 to override the enable command of the EN_
LDOA/B/C pins as shown in Table 6. For example, with
the EN_LDOA/B/C pins enabled, writing Data 5 to
Address 6 will disable LDO C and leave LDO A and LDO
B enabled. Table 6 shows the LDO disable control.
Writing Data to Addresses 7, 8, and 9 set the output voltages for LDO A, LDO B, and LDO C to one of 16 levels.
The available LDO output voltages are shown in Table 7.
Fast turn-off response time is achieved by an active output pull-down circuit, which is enabled when the LDO
regulator is disabled.
Data
1*
2
3
4
LDO C
LDO B
LDO A
Controlled by
EN_LDOA/B/C*
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C*
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C*
OFF
OFF
Controlled by
EN_LDOA/B/C
OFF
OFF
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C
Controlled by
EN_LDOA/B/C
5
OFF
6
OFF
7
OFF
OFF
8
OFF
OFF
OFF
Controlled by
EN_LDOA/B/C
OFF
Table 6: LDO Disable Control (Address 6).
Main Equals Sub (IMAIN = ISUB)
Part Number
Yes (Default)
No
AAT2866
AAT2866-3
6M+0S+2FL
5M+2S+1FL
4M+2S+2FL
n/a
Table 5: “Main Equals Sub” Control.
* denotes the register’s default (power-on-reset) value.
16
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Data
LDO VLDO[A/B/C] (V)
1
2
3
4
5*
6
7
8
9
10
11
12
13
14
15
16
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 7: LDO X Output Voltage
(Addresses 7, 8, and 9).
Flash Driver Control (Address 10 and 11)
The AAT2866 has two LED Flash channel and the
AAT2866-3 has one LED Flash channel. Each is capable
of driving 300mA per channel. Address 10 programs the
flash current level. Table 8 lists the Data Codes for the
programming Address 10. Upon startup, the power-onreset value in Address 10 is set to Data Code 13.
Once the EN/SET pin is pulled high and the AAT2866 has
turned on, the LED Flash channels can be enabled by
pulling the FL_EN to VIN. 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 Flash timer defaults to the OFF state
(DATA 16) at startup. Table 9 shows the Data Codes for
the flash safety timer.
Torch/Movie mode is automatically entered when the
flash current setting is programmed to 60mA or less per
channel (Data = 13, 14, or 15). All of the flash channels
will remain on as long as the FL_EN pin remains active.
The Flash Safety Timer can be enabled by writing
ADDR=11, DATA=1, 2, or 3. Though the AAT2866
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 other external circuitry.
Data
Flash Current (mA) per Output
1
2
3
4
5
6
7
8
9
10
11
12
13*
14
15
16
300
280
260
240
220
200
180
160
140
120
100
80
60*
40
20
OFF
Table 8: Flash Current Level (Address 10).
Data
Flash Time (sec)
1
2
3
4*
2
1
0.5
OFF
Table 9: 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 independently disabled. Normally, the backlight channels are
controlled by MAIN_OFF and SUB_OFF 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 “ON.”
In the following example we see how to turn on BL1,
BL2, BL5, and BL6. First write Address 12, Data=13 and
Address 13, Data=13 to disable BL3, BL4, FL1, and FL2.
Then program the desired current setting using Addresses
2 through 5.
* denotes the register’s default (power-on-reset) value.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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17
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Data
BL4
BL3
BL2
BL1
1*
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
ON*
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON *
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON*
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON*
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Table 10: LED Channel Disable Control, BL1-BL4 (Address 12).
Data
FL1
FL2
BL6
BL5
1*
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
ON*
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON *
ON
ON
ON
OFF
OFF
OFF
OFF
ON
ON
ON
ON
OFF
OFF
OFF
OFF
ON*
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON
ON
OFF
OFF
ON*
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Table 11: LED Channel Disable Control, BL5, BL6, FL1, BL7/FL2 (Address 13).
* denotes the register’s default (power-on-reset) value.
18
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Applications Information
PWM Control
PWM (Pulse Width Modulation) is an industry-standard
technique of controlling LED brightness by modulating
the conduction duty cycle of the LED current. LED brightness is determined by the average value of the PWM
signal multiplied by the LED’s intensity, where intensity is
proportional to the LED drive current. A PWM control
signal can be applied to the PWMM pin of the AAT2866.
By changing the duty cycle of the PWM signal from 100%
to 0% the LED current can be linearly modulated from
the programmed current setting to a floor level of 0.5mA.
Lastly, Table 12 and Figure 2 illustrate the AAT2866 LED
current control profile as a function of a PWM control
signal for 20mA programmed current setting.
EN/PWM Duty Cycle
D1-D3 Current (mA)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
20.0
18.2
16.2
14.2
12.2
10.4
8.4
6.5
4.5
2.5
AAT2866 Current Control Profile
(10kHz)
20
BLx Output Current (mA)
The AAT2866 is specifically intended for driving white
LEDs. However, the device design will allow the AAT2866
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 D1 to D4 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 AAT2866 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
Table 12: AAT2866 LED PWM Current Settings.
18
16
14
The AAT2866 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 AAT2866 soft-start feature prevents noise
transient effects associated with in-rush currents during
the start up of the charge pump circuit.
Power Efficiency and Device Evaluation
12
10
8
6
4
2
0
100
LED Selection
90
80
70
60
50
40
30
20
10
0
PWMM Input Pin Duty Cycle (%)
Figure 2: AAT2866 PWM Current Control Profile.
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 AAT2866, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT2866 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, and FL1/FL2) to derive an overall output power
measurement. For any given application, white LED forward voltage levels can differ, yet the output drive current will be maintained as a constant.
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
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 AAT2866 efficiency may be quantified under very
specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads
applied to outputs D1 through D4 for a given constant
current setting. Depending on the combination of VIN
and voltages sensed at the current sinks, the device will
operate in “Load Switch” 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.
1x Mode Efficiency
The AAT2866 1x mode is operational at all times and
functions alone to enhance device power conversion efficiency when VIN is greater then the voltage across the
load. When in 1x mode, the voltage conversion efficiency is defined as output power divided by input
power:
η=
POUT
PIN
The expression to define the ideal efficiency (η) can be
rewritten as:
η=
POUT VOUT · IOUT VOUT
=
=
PIN
VIN · IOUT
VIN
-or-
η(%) = 100
VOUT
VIN
1.5x/2x Charge Pump Mode Efficiency
The AAT2866 contains a fractional charge pump which
will boost the input supply voltage in the event where VIN
is less then the voltage required to supply the output.
The efficiency (η) can be simply defined as a linear voltage regulator with an effective output voltage that is
equal to one and a half or two times the input voltage.
Efficiency (η) for an ideal 1.5x charge pump can typically be expressed as the output power divided by the
input power.
20
η=
POUT
PIN
In addition, with an ideal 1.5x charge pump, the output
current may be expressed as 2/3 of the input current.
The expression to define the ideal efficiency (η) can be
rewritten as:
η=
POUT
VOUT · IOUT
V
=
= OUT
PIN
VIN · 1.5IOUT 1.5VIN
η(%) = 100
VOUT
1.5VIN
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%. These figures are in close agreement for output
load conditions from 1mA to 100mA. Efficiency will
decrease substantially as load current drops below 1mA
or when level of VIN approaches VOUT.
The same calculations apply for 2x mode where the
output current then becomes 1/2 of the input current.
Capacitor Selection
Careful selection of the four external capacitors CIN, C1,
C2, COUT is important because they will affect turn on
time, output ripple and transient performance. Optimum
performance will be obtained when low ESR (<100mΩ)
ceramic capacitors are used. In general, low ESR may be
defined as less than 100mΩ. A capacitor value of 1µF for
all four capacitors is a good starting point when choosing
capacitors. If the constant current sinks are only programmed for light current levels, then the capacitor size
may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the
AAT2866. 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 PCB footprint and is nonpolarized. Low ESR ceramic capacitors help to maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Equivalent Series Resistance (ESR)
Evaluation Board User Interface
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.
The user interface for the AAT2866 evaluation board is
provided by four buttons and two connection terminals.
The board is operated by supplying external power and
pressing individual buttons or button combinations. The
table below indicates the function of each button or button combination.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1µF are typically made
from NPO or C0G 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 2.2µF are
often available in low cost Y5V and Z5U dielectrics, but
capacitors greater than 1µF are typically not required for
AAT2866 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 devices can improve circuit transient
response when compared to an equal value capacitor in
a smaller package size.
Manufacturer
AVX
TDK
Murata
Taiyo Yuden
To power-on the evaluation board, connect a power supply or battery to the DC- and DC+ terminals. Close the
board’s supply connection by positioning the J1 jumper
to the ON position. 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 an external enable signal. By removing the
jumper from J2, external LDO enable signal can be
applied to the board. If PWM function is not desired,
PWMM also needs to be connected to a high potential.
When applying external enable signals, consideration
must be given to the voltage levels. The externally
applied voltages 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 OUTA/OUTB/OUTC and DC- as
opposed to some other GND in the system.
Part Number
Value
Voltage
0603ZD105K
0603ZD225K
C1608X5R1E105K
C1608X5R1C225K
C1608X5R1A475K
GRM188R61C105K
GRM188R61A225K
LMK107BJ475KA
1μF
2.2μF
1μF
2.2μF
4.7μF
1μF
2.2μF
4.7μF
10
10
25
16
10
16
10
10
Temp. Co.
Case
X5R
0603
X5R
0603
X5R
0603
X5R
0603
Table 13: Surface Mount Capacitors.
Button(s) Pushed
SW1 (LDOs)
SW2 (Backlight)
SW3 (Flash)
SW4 (Flash Enable)
Description
[Push/Release once] All LDOs will be turned on with default output voltage 1.2V. Every push release will increment output voltage according to datasheet table.
[Push/Release once] Turning on all backlight LEDs with default current 31mA per channel. Every
push release will decrement the current according to datasheet table.
[Push/Release once] Programming data to the flash LEDs with default current 300mA per channel.
Every push release will decrement the current according to datasheet table.
[Push/Release once] Turning on the flash LEDs with default timer 2sec for flash Data 1 through
Data 12. Flash Data 13, 14 and 15 will disable automatically the timer function.
Table 14: User Interface Functionality Between AAT2866 and the PIC Microcontroller.
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21
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Figure 3: AAT2866 Evaluation Board
Top Side Layout.
Figure 4: AAT2866 Evaluation Board
Bottom Side Layout.
VIN
J2 EN_LDOA/B/C
EN_LDOA/B/C
R5
10K
VIN
R1
1K
SW1
SW2
R2 R3
1K 1K
VIN
R4
1K
1
2
3
4
U2
VDD
GP5
GP4
GP3
VSS
GP0
GP1
GP2
8
7
6
5
PIC12F675
C9
1µF
R6
330
LED9
RED
SW3
SW4
ENS
FL_EN
DC-
Figure 5: AAT2866 Evaluation Board Microcontroller Schematic.
22
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
DC+
3
2
1
VIN
C10
100µF optional
lab supply bypass
J1
J4
0
VOUT
C3
2.2µF
C5
4.7µF
J3
0
C2
1.0µF
C1
1.0µF
20
21
PGND
C2-
FL2
2
C2+
3
EN/SET
BL6
4
FL_EN
BL5
5
PWMM
BL4
6
EN_LDOA/B/C
BL3
FL1
BL2
BL1
LDOA
LDOB
IN
AGND
LDOC
7
D8
19
D7
18
17
D6
16
D5
15
D4
14
D3
13
D2
D1
12
11
9
10
8
OUTC
C1-
EN_LDO_A/B/C
23
PWMM
IN
FL_EN
C1+
ENS
OUT
22
24
1
U1
AAT2866
VOUT
VINI
C8
2.2µF
Programmed
for 1.8V output
by default
OUTA
C4
4.7µF
OUTB
C7
2.2µF
Programmed
for 1.8V output
by default
C6
2.2µF
Programmed
for 1.8V output
by default
Figure 6: AAT2866 Evaluation Board Schematic.
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23
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Component
Part Number
Description
Manufacturer
U1
U2
SW1 – SW4
R1, R2, R3, R4
R5
R6
C3, C6, C7, C8
C1, C2, C9
C4, C5
D1-D6
D7, D8
LED9
J1, J2
J3
J4
AAT2866IMK
PIC12F675
PTS645TL50
Chip Resistor
Chip Resistor
Chip Resistor
GRM188R71A225KE15
GRM216R61A105KA01
GRM18x
LW M673
LXCL PWF3
CMD15-21SRC/TR8
PRPN401PAEN
Chip Resistor
Chip resistor
Backlight LED driver with 3 LDOs
8-bit CMOS, FLASH-based μC; 8-pin PDIP package
Switch Tact, SPST, 5mm
1kΩ, 5%, 1/4W; 0603
10kΩ, 5%, 1/4W; 0603
330Ω, 5%, 1/4W; 0603
2.2µF, 10V, X7R, 0603
1uF, 10V, X5R, 0603
4.7uF, 10V,X5R, 0603
Mini TOPLED White LED; SMT
Mini TOPLED Flash LED; SMT
Red LED; 1206
Conn. Header, 2mm zip
0Ω, 5%, 1/4W; 0603
0Ω, 5%, 1/2W; 0805
Skyworks
Microchip
ITT Industries
Vishay
Vishay
Vishay
MuRata
MuRata
MuRata
OSRAM
Lumileds, Philips
Chicago Miniature Lamp
Sullins Electronics
Vishay
Vishay
Table 15: AAT2866 Evaluation Board Bill of Materials (BOM).
24
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DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Ordering Information
Package
Part Marking1
Part Number (Tape and Reel)2
TQFN34-24
TQFN34-24
7GXYY
9JXYY
AAT2866IMK-T1
AAT2866IMK-3-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
TQFN34-243
3.000 ± 0.050
1.700 ± 0.050
Index Area
0.400 ± 0.050
R(5x)
2.700 ± 0.050
4.000 ± 0.050
0.210 ± 0.040
0.400 BSC
Detail “A”
Bottom View
Detail “A”
0.750 ± 0.050
Top View
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.
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25
DATA SHEET
AAT2866
Backlight/Flash LED Driver and Triple LDO Lighting Management Unit
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
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26
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