202071A.pdf

DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
General Description
Features
The AAT2862 is a highly integrated charge pump-based
lighting management unit with four linear regulators
optimized for single-cell lithium-ion/polymer systems.
The charge pump provides power for all LED outputs and
multiple LED configurations are available. The LED outputs can be programmed up to 30mA each. In addition
the two auxiliary LED output current levels can be independently programmed. An I2C serial digital interface is
used to enable, disable, and set the current to one of 32
levels. Current matching is better than 3% for uniform
display brightness.
• Input Voltage Range: 2.7V to 5.5V
• Tri-Mode Charge Pump
▪ Drives up to Eight LEDs
▪ 32 Programmable Backlight Current with Auto-fade
▪ Settings Ranging From 500μA to 30mA
▪ Two Independently Controlled Auxillary LED
Outputs
▪ 1MHz Switching Frequency
▪ Automatic Soft Start
▪ I2C Selectable Drivers
• Four Linear Regulators
▪ 200mA Output Current
▪ 200mV Dropout
▪ I2C 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
The AAT2862 also offers four high-performance lownoise MicroPower™ low dropout (LDO) linear regulators.
The regulators are enabled and their output voltages are
set through the I2C serial interface. Each LDO can supply
up to 200mA load current and ground-pin current is only
80μA making the AAT2862 ideal for battery-operated
applications.
The AAT2862 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
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
1
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Typical Application
CF1
1µF
CF2
1µF
WLEDs
VOUT
C1+ C1- C2+ C2IN
OUT
VBAT
3.6V
CIN
2.2µF
COUT
2.2µF
IN
ENABLE
I2C Serial
Interface
EN
SDA
SDA
SCL
SCL
BL1
BL2
BL3
BL4
BL5
BL6
BL7/AUX1
BL8/AUX2
LDOA
VLDOA
at 200mA
CLDOA
2.2µF
LDOB
AAT2862
LDOC
VLDOB
at 200mA
CLDOB
2.2µF
VLDOC
at 200mA
CLDOC
2.2µF
LDOD
VLDOD
at 200mA
CLDOD
2.2µF
AGND
2
PGND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Pin Descriptions
Pin #
Symbol
Function
1
OUT
O
2
C2+
I
3
4
SDA
SCL
I
I
5
EN
I
6
7
AGND
IN
G
PI
8
LDOC
O
9
LDOB
O
10
LDOA
O
11
LDOD
O
12
BL1
O
13
BL2
O
14
BL3
O
15
BL4
O
16
17
BL8/
AUX2
BL7/
AUX1
O
O
18
BL6
O
19
BL5
O
20
21
22
PGND
C2C1-
G
I
I
23
IN
PI
24
C1+
I
EP
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 AAT2862 as possible.
Positive terminal of charge pump capacitor 2. Connect the 1μF charge pump capacitor 2 from C2+ to
C2-.
I2C serial data input. SDA is the data input of the I2C serial interface. Drive SDA with the I2C data.
I2C serial clock input. SCL is the clock input of the I2C serial interface. Drive SCL with the I2C clock.
Programming Enable Input. When EN is strobed high, the backlight and LDO registers can be programmed via the I2C serial interface. When EN is strobed low, all backlight and LDO outputs are turned
off and the backlight and LDO registers are reset to their default (POR) values and forces all LDO outputs
to 0 (zero) volts.
Analog ground. Connect to PGND as close to the AAT2862 as possible.
Input power pin for all four LDOs. Connect Pin 7 to Pin 23 with as short a PCB trace as practical.
LDO C regulated voltage output. Bypass LDOC to AGND with a 2.2μF or larger ceramic capacitor as close
to the AAT2862 as possible.
LDO B regulated voltage output. Bypass LDOB to AGND with a 2.2μF or larger capacitor as close to the
AAT2862 as possible.
LDO A regulated voltage output. Bypass LDOA to AGND with a 2.2μF or larger capacitor as close to the
AAT2862 as possible.
LDO D regulated voltage output. Bypass LDOD to AGND with a 2.2μF or larger ceramic capacitor as close
to the AAT2862 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 or Auxiliary LED 8 current sink. BL8 controls the current through backlight LED 8. Connect the
cathode of backlight LED 8 to BL8. If not used, connect BL8 to OUT.
Backlight or Auxiliary 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.
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.
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.
Power ground. Connect to AGND as close to the AAT2862 as possible.
Negative terminal of charge pump capacitor 2.
Negative terminal of charge pump capacitor 1.
Power input for the charge pump. Connect IN to the input source voltage. Bypass IN to PGND with a
2.2μF or larger ceramic capacitor as close to the AAT2862 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 AAT2862 as possible.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
3
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Pin Configuration
TQFN34-24
(Top View)
PGND
C2C1IN
C1+
24
OUT
C2+
SDA
SCL
EN
AGND
IN
23
22
21
20
1
19
2
18
3
17
4
16
5
15
6
14
7
13
8
9
10
11
BL5
BL6
BL7/AUX1
BL8/AUX2
BL4
BL3
BL2
12
BL1
LDOD
LDOA
LDOB
LDOC
Programmable Options1
Main Channels
Sub Channels
Independent AUX Channels
8*
6
5
5
4
4
4
0*
2
3
2
4
3
2
0*
0
0
1
0
1
2
1. "*" denotes default values.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Absolute Maximum Ratings1
TA = 25OC unless otherwise noted.
Symbol
Description
IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6, BL7/AUX1, BL8/AUX2 Voltage to PGND and AGND
C1+, C2+ Voltage to PGND and AGND
C1-, C2-, LDOA, LDOB, LDOC, LDOD, EN, SDA, SCL Voltage to PGND and AGND
PGND 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
V
V
V
Value
Units
Thermal Information2, 3
Symbol
JA
PD
TJ
TLEAD
Description
Thermal Resistance
Maximum Power Dissipation
Operating Junction Temperature Range
Maximum Soldering Temperature (at Leads)
50
2
-40 to 150
300
O
C/W
W
C
1. 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.
2. Derate 20mW/°C above 25°C ambient temperature.
3. Mounted on a FR4 circuit board.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
5
DATA SHEET
AAT2862
Backlight LED Driver and Multiple 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
VIN
IIN(CP)
Description
Max
Units
5.5
0.20
3.0
5.0
V
mA
mA
mA
225
μA
2.7  VIN  5.5; Any One LDO ON; No Load
80
μA
EN = GND
1.0
μA
IN Operating Voltage Range
Charge Pump IN Operating
Current (Pin 23)
LDOA, LDOB, LDOC and LDOD IN
Operating Current (Pin 7)
LDOA or LDOB or LDOC or LDOD
IIN(LDOx)
IN Operating Current (Pin 7)
IN Shutdown Current
IIN(SHDN)
Over-Temperature Shutdown
TSD
Threshold
Over-Temperature Shutdown
TSD(HYS)
Hysteresis
Charge Pump Section
VOUT
OUT Output Voltage
OUT Maximum Output Current
IOUT(MAX)
BL1-BL8 Charge Pump Mode
VIN(TH_H, BL)
Transition Hysteresis
fOSC
Charge Pump Oscillator Frequency
tCP(SS)
Charge Pump Soft-Start Time
BL1-BL6, BL7/AUX1, BL8/AUX2 LED Drivers
tLED(SU)
LED Output Current Startup Time
IBL_(MAX)
BL1-BL8 Maximum Current
IBL_(DATA29)
BL1-BL8 Current
BL1-BL8 Charge Pump Transition
VBL_(TH)
Threshold
IIN(LDO)
Conditions
Min
Typ
2.7
1x Mode; 3.0  VIN  5.5; LDOs OFF; No Load
1.5x Mode; 3.0  VIN  5.5; LDOs OFF; No Load
2x Mode; 3.0  VIN  5.5; LDOs OFF; No Load
0.15
2.7  VIN  5.5; All LDOs ON; No Load
140
°C
15
°C
VIN = 3.0V, VOUT = 4.0V
5.2
800
V
mA
EN/SET = IN; VIN – VF = 1V
300
mV
Address 07h Data=20 (0010 0000); TA = 25°C
TA = 25°C
1.2
100
MHz
μs
OUT: 0V to IN
Address 03h Data=E0 (1110 0000)
Address 03h Data=FD (1111 1101)
Address 03h Data=E0 (1110 0000)
27
1.75
20
30
1.94
33
2.13
180
us
mA
mA
mV
1. The AAT2862 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.
6
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
DATA SHEET
AAT2862
Backlight LED Driver and Multiple 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
LDOA, LDOB, LDOC, LDOD Output
ΔVLDO[A/B/C,D]
/VLDO[A/B/C,D]
Voltage Tolerance
LDOA, LDOB, LDOC, LDOD Maximum
ILDO[A/B/C,D](MAX)
Load Current
LDOA, LDOB, LDOC, LDOD Dropout
VLDO[A/B/C,D](DO)
Voltage2
VLDO/
LDOA, LDOB, LDOC, LDOD Line
VLDO*VIN
Regulation
LDOA, LDOB, LDOC, LDOD Power SupPSRR[A/B/C,D]
ply Rejection Ratio
LDOA, LDOB, LDOC, LDOD AutoROUT_(DCHG)
Discharge Resistance
I2C Logic and Control Interface
VIL
SDA, SCL, EN Input Low Threshold
VIH
SDA, SCL, EN Input High Threshold
VOL
SDA Output Low Voltage
IIN
SDA, SCL, EN Input Leakage Current
fSCL
SCL Clock Frequency
tLOW
SCL Clock Low Period
tHIGH
SCL Clock High Period
tHD_STA
Hold Time START Condition
Setup Time for Repeat START
tSU_STA
tSU_DAT
SDA Data Setup Time
tHD_DAT
SDA Data HOLD Time
tSU_STO
Setup Time for STOP Condition
Bus Free Time Between STOP and
tBUF
START Conditions
Conditions
Min
IOUT = 1mA to 200mA; TA = 25°C
IOUT = 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/D] ≥ 3.0V; IOUT = 150mA
75
VLDO = (VOUT[A/B/C/D] + 1V) to 5V
ILDO[A/B/C/D] =10mA, 1kHz
2.7V ≤ VIN ≤ 5.5V
2.7V ≤ VIN ≤ 5.5V
IPULLUP = 3mA
VSDA = VSCL = VLED_SEL = VLDO_SEL = IN = 5V
mA
200
mV
0.09
%/V
50
dB
20
Ω
0.4
1.4
-1
0
1.3
0.6
0.6
0.6
100
0
0.6
0.4
1
400
0.9
1.3
V
V
V
μA
kHz
μs
μs
μs
μs
ns
μs
μs
μs
1. The AAT2862 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/D] is defined as VIN – LDO[A/B/C/D] when LDO[A/B/C/D] is 98% of nominal.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
I2C Interface Timing Details
t
t
t
8
t
t
t
t
t
t
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
Backlight Efficiency vs. Input Voltage
Backlight Current Matching vs. Temperature
100
Efficiency (%)
90
80
70
60
50
30mA/ch, VF = 3.85V
20.32mA/ch, VF = 3.55V
4.84mA/ch, VF = 3.0V
40
30
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Backlight Output Current (mA)
(VIN = 3.6V; 30mA/ch)
33
32
31
30
29
28
Channel 1 - Channel 8
27
26
25
-40
-15
10
35
60
Temperature (°C)
Input Voltage (V)
Charge Pump Output Turn On Characteristic
Turn On to 1x Mode Backlight
(VIN = 3.6V; ILED = 0mA; COUT = 2.2µF)
(VIN = 4.5V; 30mA/ch)
VEN (top) (V)
2.0
4.0
3.0
2.0
1.0
0.0
Charge Pump Output
(bottom) (V)
4.0
0.0
SDA
(2V/div)
0V
VOUT
(2V/div)
VSINK
(2V/div)
0V
IIN
(100mA/div)
0A
Time (50µs/div)
Time (200µs/div)
Turn On to 1.5x Mode Backlight
Turn On to 2x Mode Backlight
(VIN = 3.5V; 30mA/ch)
(VIN = 3.2V; 30mA/ch)
SDA
(2V/div)
85
SDA
(2V/div)
0V
0V
VOUT
(2V/div)
VOUT
(2V/div)
VSINK
(2V/div)
0V
VSINK
(2V/div)
0V
IIN
(100mA/div)
0A
IIN
(200mA/div)
0A
Time (200µs/div)
Time (200µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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9
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
(VIN = 3.3V; 30mA/ch Backlight; 1.5x Mode;
COUT = 2.2µF; fOSC = 1.2MHz)
Input Voltage (AC coupled)
(top) (mV)
Operating Characteristic
(VIN = 3.5V; 30mA/ch)
0V
VDIODE
(2V/div)
0V
IIN
(200mA/div)
20
10
0
50
0
-50
0A
Time (500ns/div)
Time (200µs/div)
20
10
0
20
10
0
-10
-20
LDO Output Voltage Deviatoin (%)
LDOA/B/C/D Output Voltage vs. Temperature
Charge Pump Output Voltage
(AC coupled) (bottom) (mV)
Input Voltage (AC coupled)
(top) (mV)
Operating Characteristic
(VIN = 3.0V; 30mA/ch Backlight; 2x Mode;
COUT = 2.2µF; fOSC = 1.2MHz)
(VIN = 3.6V; ILDO = 0mA)
1.5
1
0.5
0
-0.5
VOUT = 1.8V
VOUT = 3.3V
-1
-1.5
-40
-15
10
85
LDO A/B/C/D Line Regulation
(VIN = 3.6V)
(ILDO = 10mA)
1.5
VOUT = 1.2V
VOUT = 3.3V
1.0
0.5
0.0
-0.5
-1.0
-1.5
1
10
100
1000
LDO Output Voltage Deviation (%)
LDO Output Voltage Deviation (%)
60
LDO A/B/C/D Load Regulation
Load Current (mA)
10
35
Temperature (°C)
Time (500ns/div)
0.1
Charge Pump Output Voltage
(AC coupled) (bottom) (mV)
VEN
(2V/div)
Turn Off from 1.5x Mode Backlight
1.5
VOUT = 1.8V
VOUT = 3.3V
1.0
0.5
0.0
-0.5
-1.0
-1.5
2.7
3.1
3.5
3.9
4.3
4.7
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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5.1
5.5
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Typical Characteristics
LDO A/B/C/D Line Transient Response
(VIN = 3.6V to 4.2V; ILDO = 10mA; VOUT = 1.8V; CLDO = 2.2µF)
0
2.00
1.90
1.80
1.70
4.4
Input Voltage
(top) (V)
100
4.0
3.6
1.82
1.81
1.80
1.79
1.78
1.60
Time (20µs/div)
Time (1ms/div)
LDO A/B/C/D Turn On Characteristic
LDO A/B/C/D Turn On Characteristic
(VIN = 3.6V; VOUT = 1.8V; CLDO = 2.2µF)
(VIN = 3.6V; VOUT = 3.3V; CLDO = 2.2µF)
1.5
1.0
0.5
0.0
VSDA (top) (V)
VSDA (top) (V)
2.0
4.0
2.0
3.0
2.0
1.0
0.0
Time (20µs/div)
Time (20µs/div)
EN, SDA, SCL Input Low Threshold Voltage
vs. Input Voltage
1.4
1.2
1.3
1.1
1.2
1.1
1.0
0.9
0.8
-40°C
25°C
85°C
0.6
0.5
0.4
2.7 2.9 3.1 3.3
3.5 3.7 3.9 4.1 4.3 4.5
Input Voltage (V)
4.7 4.9 5.1 5.3 5.5
VEN(L), VSDA(L), VSCL(L) (V)
VEN(H), VSDA(H), VSCL(H) (V)
EN, SDA, SCL Input High Threshold Voltage
vs. Input Voltage
0.7
4.0
0.0
LDO Output (bottom) (V)
2.0
LDO Output (bottom) (V)
4.0
0.0
LDO Output Voltage
(bottom) (V)
200
LDO Output Voltage
(bottom) (V)
LDO Output Current
(top) (mA)
LDO A/B/C/D Load Transient Response
(ILDO = 10mA to 200mA; VIN = 3.6V; VOUT = 1.8V; CLDO = 2.2µF)
1.0
0.9
0.8
0.7
0.6
0.5
-40°C
25°C
85°C
0.4
0.3
0.2
2.7 2.9 3.1 3.3
3.5 3.7 3.9 4.1 4.3 4.5
4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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11
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Functional Block Diagram
IN IN
LDOA
C1C1+
C2-
1x/1.5x/2x
Tri-mode
Charge Pump
C2+
LDOB
OUT
LDOC
LDOD
REF
8
BL1
SDA
BL2
SCL
BL3
BL4
EN
Control
Logic
BL5
BL6
BL7/AUX1
BL8/AUX2
PGND
12
AGND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202071A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Functional Description
LED Current Control
The AAT2862 is a highly integrated backlight driver with
four LDO regulators. The charge pump LED driver powers the backlight LEDs from the 2.7V to 5.5V input voltage. The LDO regulators get their power from the same
input and produce regulated output voltage between
1.2V and 3.3V. Control of the LEDs and the LDO output
voltage is through an I2C serial interface for easy programming.
The eight backlight LED channels are programmed
through the I2C serial interface and can be set between
0.5 and 30mA in ~1mA steps. The currents match to
within typically 3%. There are fade-in and fade-out timers
that can be programmed through the interface as well.
See the “I2C Serial Interface” section for more information on setting the LED currents.
LDO Regulators
LED Drivers
The AAT2862 drives up to eight backlight LEDs up to
30mA each. The LEDs are driven from a charge pump to
insure that constant current is maintained over the
entire battery voltage range. The charge pump automatically switches from 1x, 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.
Depending on the battery voltage and LED forward voltage, the charge pump drives the LEDs directly from the
input voltage (1x or bypass mode) or steps up the input
voltage by a factor of 1.5 (1.5x mode) or 2 (2x mode).
The charge pump requires only two tiny 2.2μF ceramic
capacitors, making a more compact solution than an
inductor-based step-up converter solution. 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 180mV, 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 AAT2862 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 modetransition hysteresis that prevents the charge pump
from oscillating between modes.
The AAT2862 includes four low dropout (LDO) linear
regulators. These regulators are powered from the battery and produce a fixed output voltage set through the
I2C serial interface. The output voltages can be programmed to one of 16 output voltages between 1.2V
and 3.3V. The LDOs can also be turned on/off through
the I2C serial interface.
The LDO regulators require only a small 2.2μF ceramic
output capacitor for stability. If improved load transient
response is required, larger-valued capacitors can be
used without stability degradation.
I2C Serial Interface
The AAT2862 uses an I2C serial interface to set the LED
currents, the LDO's output voltages, and to turn on/off
all LDOs, as well as other housekeeping functions. The
I2C interface takes input from a master device while the
AAT2862 acts as a target to the master.
The I2C protocol uses two open-drain inputs; SDA (serial data line) and SCL (serial clock line). Both inputs
require an external pull up resistor, typically to the input
voltage. The I2C protocol is bidirectional and allows target devices and masters to both read and write to the
bus. The AAT2862 only supports the write protocol;
therefore, the Read/Write bit must always be set to “0”.
The timing diagram in Figure 1 shows the typical transmission protocol.
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
start
msb Chip Address lsb
w
AAT2862 Device Address = 60 h
w
ack
msb Register Add lsb
ack
msb DATA lsb
ack
stop
SCL
SDA
start
ack
Addr = 00h
ack
Data = 06 h
ack
stop
Figure 1: Typical I2C Timing Diagram.
I2C Serial Interface Protocol
START and STOP Conditions
The I2C serial interface protocol is shown in Figure 1.
Devices on the bus can be either master or target devices. Both master and target devices can both send and
receive data over the bus, with the difference being that
the master device controls all communication on the
bus. The AAT2862 acts as a target device on the bus and
is only capable of receiving data and does not transmit
data over the bus.
START and STOP conditions are always generated by the
master. Prior to initiating a START, both the SDA and SCL
pin are inactive and are pulled high through external pullup resistors. As shown in Figure 1, a START condition is
when the master pulls the SDA line low and, after the
start condition hold time (tHT_STA), the master strobes the
SCL line low. A START condition acts as a signal to devices on the bus that the device producing the START condition is active and will be communicating on the bus.
The I2C communications begin with the master making a
START condition. Next, the master transmits the 7-bit
device address and a Read/Write bit. Each target device
on the bus has a unique address. The AAT2862 device
address is 60h.
If the address transmitted by the master matches the
device address, the target device transmits an
Acknowledge (ACK) signal to indicate that it is ready to
receive data. Since the AAT2862 only reads from the
master, the Read/Write bit must be set to “0”. Next, the
master transmits the 8-bit register address, and the target device transmits an ACK to indicate that it received
the register address. Next, the master transmits the
8-bit data word, and again the target device transmits
an ACK indicating that it received the data. This process
continues until the master is finished writing to the target device, at which time the master generates a STOP
condition.
14
A STOP condition, as shown in Figure 1, is when SCL
changes from low to high followed after the STOP condition setup time (tSU_STO), by an SDA low-to-high transition. The master does not issue an ACK and releases SCL
and SDA.
Transferring Data
Addresses and data are sent with the most significant bit
first transmitted and the least significant bit transmitted
last. After each address or data transmission, the target
device transmits an ACK signal to indicate that it has
received the transmission. The ACK signal is generated
by the target after the master releases the SDA data line
by driving SDA low.
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
STOP
START
SDA
SDA
SCL
SCL
Figure 2: I2C STOP and START Conditions;
START: A High “1” to Low “0” Transition on the SDA Line While SCL is High “1”
STOP: A Low “0” to High “1” Transition on the SDA Line While SCL is High “1”.
SCL
1
2
3
4
5
6
7
MSB
SDA
A6
8
9
LSB
A5
A4
A3
A2
A1
A0
R/W
ACK
Device Address
Figure 3: I2C Address Bit Map;
7-bit Slave Address (A6-A0), 1-bit Read/Write (R/W), 1-bit Acknowledge (ACK).
SCL
1
2
3
4
5
6
7
MSB
SDA
D7
8
9
LSB
D6
D5
D4
D3
D2
D1
D0
ACK
Register Address /
Data
Figure 4: I2C Register Address and Data Bit Map;
8-bit Data (D7-D0), 1-bit Acknowledge (ACK).
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Applications Information
Backlight Control Registers
The AAT2862 has five backlight registers:
I2C Serial Programmed Registers
• REG3 (I2C address 03h)
• REG4 (I2C address 04h)
• REG5 (I2C address 05h)
backlight.
• REG6 (I2C address 06h)
backlight.
• REG7 (I2C address 07h)
and fade-out function.
The AAT2862 I2C programmable registers are listed in
Table 1. There are eight registers, five for the backlight
LED control, and three to control the four LDOs.
All backlight channels can be easily configured in many
different ways through the I2C interface. The default
assignment for the drivers is four backlight for Main, two
backlight for Sub, and two extra that can be applied to
Main, Sub, or Auxiliary. All eight backlight channels can
be driven to the same current level by writting the MEQS
= 1 bit in REG3. The Main and Sub backlights can be
programmed independently to one of 32 levels described
in Table 2.
controls Main backlight.
controls Sub backlight.
controls auxiliary Aux1
controls auxiliary Aux2
controls backlight fade-in
Register
Number
Hex
Address
REG0
00h
REG1
01h
REG2
02h
REG3
03h
REG4
04h
REG5
05h
REG6
06h
REG7
07h
Functional
Description
LDO A & B
Output Voltage
Control
LDO C & D
Output Voltage
Control
LDO EN control
Backlight
Current Control
MAIN
Backlight
Current Control
SUB
Backlight
Current Control
AUX1
Backlight
Current Control
AUX2
Backlight Fade
Control
Data
Bit7
Data
Bit6
Data
Bit5
Data
Bit4
Data
Bit3
Data
Bit2
Data
Bit1
Data
Bit0
LDOA[3]
LDOA[2]
LDOA[1]
LDOA[0]
LDOB[3]
LDOB[2]
LDOB[1]
LDOB[0]
LDOC[3]
LDOC[2]
LDOC[1]
LDOC[0]
LDOD[3]
LDOD[2]
LDOD[1]
LDOD[0]
X
X
X
X
ENLDO_D
ENLDO_C
ENLDO_B
ENLDO_A
MEQS
DISABLE
FADE_
MAIN
MAIN_ON
BLM[4]
BLM[3]
BLM[2]
BLM[1]
BLM[0]
X
DISABLE
FADE_SUB
SUB_ON
BLS[4]
BLS[3]
BLS[2]
BLS[1]
BLS[0]
AUX1[1]
AUX1[0]
AUX1_ON
BLA1[4]
BLA1[3]
BLA1[2]
BLA1[1]
BLA1[0]
AUX2[2]
AUX2[0]
AUX2_ON
BLA2[4]
BLA2[3]
BLA2[2]
BLA2[1]
BLA2[0]
X
X
FADE_
TIME[1]
FADE_TIME[0]
FADE_MAIN
FADE_SUB
FLOOR[1]
FLOOR[0]
Table 1: AAT2862 Configuration/Control Register Allocation (“X” = “Reserved”).
16
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Data Bit4
Data Bit3
Data Bit2
Data Bit1
Data Bit0
LED Current (mA)
BLM[4]
BLM[3]
BLM[2]
BLM[1]
BLM[0]
REG3
BLS[4]
BLS[3]
BLS[2]
BLS[1]
BLS[0]
REG4
BLA1[4]
BLA1[3]
BLA1[2]
BLA1[1]
BLA1[0]
REG5
BLA2[4]
BLA2[3]
BLA2[2]
BLA2[1]
BLA2[0]
REG6
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
30*
29.03
28.06
27.10
26.13
25.16
24.19
23.23
22.26
21.29
20.32
19.35
18.38
17.42
16.45
15.48
14.52
13.55
12.58
11.61
10.65
9.68
8.71
7.74
6.77
5.81
4.84
3.87
2.9
1.94
0.97
0.48
Table 2: Main/Sub/Aux Backlight LED Current - BLM/BLS/BLA1,2[4:0].
Table 3 describes the floor current per channel for the
fade-in and fade-out functions. In fade-out sequence
floor will be the final current that will continue to be
present until the Main, Sub or Aux1,2 channels are disabled by writing MAIN_ON = 0 to REG3, SUB_ON = 0 to
REG4, A1_ON = 0 to REG5, and/or A2_ON = 0 to REG6.
In fade-in sequence floor is the direct current all chan-
nels will be turned on by writing MAIN_ON = 1 to REG3,
SUB_ON = 1 to REG4, A1_ON = 1 to REG5, and/or
A2_ON = 1 to REG6.
Fade-out can be initiated only after the fade in sequence
has been programmed first by writing FADE_MAIN = 1
and/or FADE_SUB = 1 as is shown in Table 4.
*Denotes default (power-on-reset) value.
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Data Bit1
Data Bit0
Fade In and Out
Current Level (mA)
FLOOR[1]
FLOOR[0]
REG7
0*
0
1
1
0*
1
0
1
0.48*
0.97
1.94
2.90
Table 3: Main/Sub LED Current
Fade In and Out Level Control.
Data Bit6 of REG3 and REG4 enables the fade in and out
control of the Main and Sub channels. Fade function is
enabled by default and can be explicitly disabled by writing DISABLE FADE_MAIN = 1 and/or DISABLE FADE_SUB
= 1 as shown in Table 6.
Data Bit6
Backlight Channel Fade In
and Out Enable/Disable
DISABLE FADE_MAIN
REG3
DISABLE FADE_SUB
REG4
0*
1
Enable*
Disable
Fade In and Out Control
Data Bit3
Data Bit2
FADE_MAIN
FADE_SUB
Main
Sub
0*
0
1
1
0*
1
0
1
Fade Out*
Fade Out
Fade In
Fade In
Fade Out*
Fade In
Fade Out
Fade In
REG7
Table 6: Main/Sub Current Fade ON/OFF Control.
Table 4: Main/Sub LED Current
Fade In and Out Control.
Data Bit5 of REG3, REG4, REG5 and REG6 controls the
turn on and off of the Main, Sub, Aux1 and Aux2 channels according to Table 5. Both Aux1 and Aux2 channels
are considered part of the Sub backlight channels unless
explicitly turned on as part of the Main backlight or independently.
Data Bit5
Backlight Channel ON/OFF
MAIN_ON
REG3
SUB_ON
REG4
AUX1_ON
REG5
AUX2_ON
REG6
0*
1
OFF*
ON
Table 5: Main/Sub/Aux1/Aux2 LED Current
ON/OFF Control.
Data Bit7=1 of REG3 programs all Sub channels as Main
backlight as described in Table 7. If the Main fade-in or
fade-out function is enabled; all eight Main and Sub
channels will be faded-in or out simultaneously.
Data Bit7
MAIN Equal SUB (MEQS)
MEQS
REG3
0*
1
False*
True
Table 7: Main/Sub Current Fade ON/OFF Control.
Data Bit4 and Data Bit5 of REG7 control the duration of
the fade-in/out function. The default timing is 850ms
with options for 650ms and 425ms according to Table 8.
The charge pump oscillator frequency is related to the
fade-in/out timing as follows:
For the 850ms fade-in/out timer, typical fOSC = 600kHz
For the 650ms fade-in/out timer, typical fOSC = 800kHz
For the 425ms fade-in/out timer, typical fOSC = 1.2MHz
respectively.
Data Bit5
Data Bit4
FADE_TIME[1]
FADE_TIME[0]
Fade In and Out
Timing (ms)
0*
0
1
1
0*
1
0
1
850*
650
425
850
Table 8: Main/Sub LED Current
Fade In and Out Timing
*Denotes default (power-on-reset) value.
18
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Examples of Fade-Out Programming
Examples of Fade-In/Out Programming
Main Only (Sub is OFF):
Main Only (Sub is OFF):
Address
Address
Address
Address
Address
03h, Data 40: Disable fade
07h, Data 08: Fade-in is programmed
03h, Data 6F: Turn on directly to 15.48mA/ch
03h, Data 20: Re-enable fade
07h, Data 00: Fade-out to 0.48mA/ch
Sub Only (Main is OFF):
Address
Address
Address
Address
Address
04h, Data 40: Disable fade
07h, Data 04: Fade-in is programmed
04h, Data 6F: Turn on directly to 15.48mA/ch
04h, Data 2F: Enable fade
07h, Data 02: Fade-out to 1.94mA/ch
Main and Sub (as shown in Figure 5):
Address
Address
Address
Address
Address
03h,
07h,
03h,
03h,
07h,
Data
Data
Data
Data
Data
C0:
0C:
60:
20:
03:
Address 03h, Data 20: Main backlight is turned on
with 0.48mA/ch
Address 07h, Data 08: Fade-in to 30mA/ch
Address 07h, Data 03: Fade-out to 2.90mA/ch
Sub Only (Main is OFF):
Address 07h, Data 02: Fade-in is programmed to
1.94mA/ch
Address 04h, Data 2E: Sub backlight is turned on with
1.94mA/ch
Address 07h, Data 04: Fade-in to 16.45mA/ch
Address 07h, Data 02: Fade-out to 1.94mA/ch
Main and Sub (as shown in Figure 6):
Disable fade
Fade-in is programmed
Turn on directly to 30mA/ch
Enable fade
Fade-out to 2.90mA/ch
Address 07h, Data 01: Fade-in is programmed to
0.97mA/ch
Address 03h, Data AA: Main and Sub backlight is
turned on with 0.97mA/ch
Address 07h, Data 0C: Fade-in to 20.32mA/ch
Address 07h, Data 01: Fade-out to 0.97mA/ch
Main and Sub Fade Out Only
Max. 30mA /ch to 2.90mA/ch
I2C Sequence:
AAT2862 Chip Address 60h
REG3 Address 03h, Data C0(0100 0000): Disable fade function
REG7 Address 07h, Data 0C(0000 1100): Fade-in is programmed
REG3 Address 03h, Data 60(0110 0000): Main/Sub is turned on with 30mA/ch
Main/Sub Backlight
30mA/ch
REG3 Address 03h, Data 20(0010 0000): Enable fade function
REG7 Address 07h, Data 03(0000 0011): Fade-out is programmed to 2.90mA/ch
Main/Sub Backlight
2.90mA/ch
REG3 Address 03h Data 00(0000 0000 )
REG3 Address 03h, Data 20(0010 0000): Enable fade function
REG3 Address 03h, Data 60(0110 0000): Main/Sub is turned on with 30mA/ch
REG7 Address 07h, Data 08(0000 1000): Fade-in is programmed
REG3 Address 03h, Data C0(0100 0000): Disable fade function
REG7 Address 07h, Data 0C(0000 1100): Fade-in is programmed
REG3 Address 03h, Data 60(0110 0000): Main/Sub is turned on with 30mA/ch
Main/Sub Backlight
Off
Figure 5: Example of AAT2862 Fade Out Programming.
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Main and Sub Fade In/Out
Max. 20.32mA/ch to 0.97mA/ch
I2C Sequence:
AAT2862 Chip Address 60h
REG7 Address 07h, Data 01(0000 0001): Fade-in is programmed as 0.97mA/ch
REG3 Address 03h, Data AA(1010 1010): Main/Sub backlight is turned on with 0.97mA/ch
REG7 Address 07h, Data 0C(0000 1100): Fade-in programmed to 20.32mA/ch
Main/Sub Backlight
20.32mA/ch
REG7 Address 07h, Data 01(0000 0001): Fade-out is programmed to 0.97mA/ch
REG7 Address 07h, Data 0C(0000 1100):
Fade-in is programmed as 20.32mA/ch
Main/Sub Backlight
0.97mA/ch
REG3 Address 03h Data 80(1000 0000)
REG7 Address 07h, Data 01(0000 0001): Fade-in is programmed as 0.97mA/ch
REG3 Address 03h, Data AA(1010 1010): Main/Sub backlight is turned on with 0.97mA/ch
REG7 Address 07h, Data 0C(0000 1100): Fade-in is programmed to 20.32mA/ch
Main/Sub Backlight
Off
Figure 6: Example of AAT2862 Fade In/Out Programming.
LDO Control Registers
The four LDO regulators have three dedicated control
registers:
• REG0 (I2C address 00h) and REG1 (I2C address 01h)
set the output voltages of LDOA/B/C/D to one of 16
pre-set values according to Table 9 and Table 10.
• REG2 (I2C address 02h) controls turning on/off of
LDOA/B/C/D regulators according to Table 11.
20
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Data
Bit7
Data
Bit6
Data
Bit5
Data
Bit4
LDO
VLDO[A/C]
(V)
Data
Bit3
Data
Bit2
Data
Bit1
Data
Bit0
LDO
VLDO[B/D]
(V)
LDOA[3]
LDOA[2]
LDOA[1]
LDOA[0]
REG0
LDOB[3]
LDOB[2]
LDOB[1]
LDOB[0]
REG0
LDOC[3]
LDOC[2]
LDOC[1]
LDOC[0]
REG1
LDOD[3]
LDOD[2]
LDOD[1]
LDOD[0]
REG1
0*
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0*
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0*
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0*
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1.2*
1.3
1.5
1.6
1.8
2.0
2.2
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
0*
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0*
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0*
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0*
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
1.2*
1.3
1.5
1.6
1.8
2.0
2.2
2.5
2.6
2.7
2.8
2.9
3.0
3.1
3.2
3.3
Table 9: LDOA/LDOC Output Voltage Control Data.
Table 10: LDOB/LDOD Output Voltage Control Data.
Data Bit3
Data Bit2
Data Bit1
Data Bit0
ENLDO_D
ENLDO_C
ENLDO_B
ENLDO_A
LDOD Output
LDOC Output
LDOB Output
LDOA Output
0*
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0*
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0*
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0*
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Off*
Off
Off
Off
Off
Off
Off
Off
On
On
On
On
On
On
On
On
Off*
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
Off*
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off
Off
On
On
Off*
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Off
On
Table 11: LDOA/LDOB/LDOC/LDOD ON/OFF Control Data.
*Denotes default (power-on-reset) value.
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21
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Auxillary Backlight Selection
Each of the auxiliary drivers (Aux1, Aux2) can also be
programmed to one of the 32 levels described in Table 2.
The auxiliary drivers can be driven independently, or
combined with the main or sub by changing Data Bit6
and Data Bit7 in REG5 (I2C address 05h) and REG6 (I2C
address 06h) according to Table 12.
Data
Bit7
Data
Bit6
Auxillary Channel
Assignment
AUX1[1]
AUX1[0]
REG5
AUX2[1]
AUX2[0]
0*
0*
0
1
1
0
1
1
REG6
IAUX1 = Sub*
IAUX2 = Sub*
IAUX1 = Main
IAUX2 = Main
IAUX1 = Aux1
IAUX2 = Aux2
The low-dropout current sinks in the AAT2862 maximize
performance and make it capable of driving LEDs with
high forward voltages. Multiple channels can be combined to obtain a higher LED drive current without complication.
Device Switching Noise Performance
The AAT2862 operates at three fixed frequencies, typically 600kHz, 800kHz, and 1.2MHz, in order to help
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-topeak, typically ten times less than inductor-based DC/DC
boost converter white LED backlight solutions. The
AAT2862 soft-start feature prevents noise transient
effects associated with in-rush currents during the start
up of the charge pump circuit.
Reserved
Table 12: Auxiliary Channel Assignment.
LED Selection
The AAT2862 is specifically intended for driving white
LEDs. However, the device design will allow the AAT2862
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 D8 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.
Power Efficiency and Device Evaluation
Charge-pump efficiency discussion in the following sections accounts only for the efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT2862, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT2862 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
BL8) to derive an overall output power measurement.
For any given application, white LED forward voltage
levels can differ, yet the output drive current will be
maintained as a constant.
This makes quantifying output power a difficult task
when taken in the context of comparing to other white
LED driver circuit topologies. A better way to quantify
total device efficiency is to observe the total input power
to the device for a given LED current drive level. The
best White LED driver for a given application should be
based on trade-offs of size, external component count,
reliability, operating range and total energy usage...not
just “% efficiency”.
*Denotes default (power-on-reset) value.
22
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
The AAT2862 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 D8 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.
Refer to the following two sections for explanations of
each operational mode.
1x Mode Efficiency
The AAT2862 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 () can be
rewritten as:
η=
POUT VOUT · IOUT VOUT
=
=
PIN
VIN · IOUT
VIN
-or-
η(%) = 100
⎛ VOUT ⎞
⎝ VIN ⎠
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 () can be
rewritten as:
η=
POUT
VOUT · IOUT
VOUT
=
=
VIN · 1.5IOUT
1.5VIN
PIN
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, and COUT is important because they will affect turn on
time, output ripple and transient performance. Optimum
performance will be obtained when low ESR (<100m)
ceramic capacitors are used. In general, low ESR may be
defined as less than 100m. 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
1.5x/2x Charge Pump Mode Efficiency
The AAT2862 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 () 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 () for an ideal 1.5x charge pump can typically be expressed as the output power divided by the
input power.
η=
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the
AAT2862. 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 maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
POUT
PIN
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23
DATA SHEET
AAT2862
Backlight LED Driver and Multiple 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 AAT2862 evaluation board is
provided by three buttons and three connection terminals. The board is operated by supplying external power
and pressing individual buttons or button combinations.
Table 14 indicates the function of each button or button
combination.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1F are typically made
from NPO or COG materials. NPO and COG 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 2.2F are often
available in low cost Y5V and Z5U dielectrics, but capacitors greater than 1F are typically not required for
AAT2862 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 data, clock and enable lines from the
microcontroller and apply external signal sources by
removing the jumpers from J2, J3 and/or J4. External
enable signal must be applied to the ON pin of J4 terminal. External I2C clock SCL can be applied to J2 pin and
data SDA to J3 pin.
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 LDOA/LDOB/LDOC/LDOD 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.
24
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Button(s) Pushed
SW1 (LDOs)
SW2 (Main Backlight)
SW3 (Sub Backlight)
SW1 + SW2
SW1 + SW3
SW1 + SW2 + SW3
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 the Main and Sub backlight LEDs with default current 30mA per
channel. Every push release will decrement the current according to datasheet table.
[Push/Release once] Turning on only the Sub backlight LEDs with default current 30mA. Every push
release will decrement the current according to datasheet table.
[Push/Release once] Turning on the fade-out sequence of the backlight LEDs with default current
30mA down to 0.5mA per channel.
[Push/Release once] Turning on the fade-in sequence of the backlight LEDs with default current
0.5mA up to 30mA per channel.
[Push/Release once] Reset all registers to default.
Table 14: AAT2862 Evaluation Board User Interface Functionality.
DC+
1
2
3
VIN
C5
4.7µF
C11
100µF (optional)
100µF lab supply bypass
J1
VOUT
C3
2.2µF
C2
1.0µF
C1
1.0µF
20
PGND
C2+
SDA
SCL
BL5
D6
BL7/AUX1
17
D7
BL8/AUX2
16
D8
15
D4
14
D3
13
D2
BL6
BL4
BL3
AGND
BL1
LDOD
LDOA
LDOB
IN
D5
19
18
EN
LDOC
7
C2-
6
21
EN
5
C1-
SCL
4
22
3
IN
SDA
OUT
C1+
2
23
24
1
U1
AAT2862
BL2
12
11
9
8
10
D1
C4
4.7µF LDOC
VOUT
LDOD
C9
2.2µF
C8
2.2µF
LDOB
LDOA
C7
2.2µF
C6
2.2µF
Figure 7: AAT2862 Evaluation Board Schematic.
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25
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
VIN
R1
1K
R2
1K
R3
1K
VIN
1
2
SW1
3
4
SW2
U2
VDD
GP5
GP4
GP3
PIC12F675
VSS
GP0
GP1
GP2
C10
1µF
8
R7
330
VIN
7
6
5
LED9
RED
R5
10K
SW3
J2
R4
10K
SCL
SCL
SDA
VIN
DC-
J3
SDA
J4
EN
EN
R6
100K
Figure 8: AAT2862 Evaluation Board Microcontroller Schematic.
26
Figure 9: AAT2862 Evaluation Board
Figure 10: AAT2862 Evaluation Board
Top Side Layout.
Bottom Side Layout.
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DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Component
Part Number
Description
Manufacturer
U1
U2
SW1 – SW3
R1, R2, R3
R4, R5
R6
R7
C3, C6, C7, C8, C9
C1, C2
C4, C5
D1-D8
LED9
J1, J2, J3, J4
AAT2862IMK
PIC12F675
PTS645TL50
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
GRM188R71A225KE15
GRM216R61A105KA01
GRM18x
LW M673
CMD15-21SRC/TR8
PRPN401PAEN
Backlight LED driver with 4 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
100kΩ, 5%, 1/4W; 0603
300Ω, 5%, 1/4W; 0603
2.2μF, 10V, X7R, 0603
1μF, 10V, X5R, 0603
4.7μF, 10V,X5R, 0603
Mini TOPLED White LED; SMT
Red LED; 1206
Conn. Header, 2mm zip
Skyworks
Microchip
ITT Industries
Vishay
Vishay
Vishay
Vishay
Murata
Murata
Murata
Osram
Chicago Miniature Lamp
Sullins Electronics
Table 15: AAT2862 Evaluation Board Component Listing.
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27
DATA SHEET
AAT2862
Backlight LED Driver and Multiple LDO Lighting Management Unit
Ordering Information
Package
Part Marking1
Part Number (Tape and Reel)2
TQFN34-24
6RXYY
AAT2862IMK-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”
Detail “A”
Bottom View
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.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
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PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
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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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Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
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