AAT2861IMK-1-T1 - Skyworks Solutions, Inc.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

General Description

The AAT2861 is a highly integrated charge pump-based

lighting management unit (LMU) offering eight LED

channels with three linear regulators optimized for sin-

gle-cell lithium-ion/polymer systems. The charge pump

provides power for all LED outputs; multiple backlight

and flash LED configurations are available. The backlight

LED outputs can be programmed up to 31mA each and

the flash LED output current can be programmed up to

600mA total. Skyworks' AS2Cwire™ (Advanced Simple

Serial Control™) single-wire interface is used to enable,

disable, and set the current to one of 32 levels for the

backlight and one of 16 levels for the flash. A program-

mable safety timer and separate flash control input are

included for easy flash control. Backlight current match-

ing is better than 3% for uniform display brightness, and

flash current matching is better than 5% for uniform

power dissipation.

The AAT2861 also offers three high-performance low-

noise MicroPower™ LDO linear regulators. The regulators

output voltages are set through the AS2Cwire serial

interface. Each LDO can supply up to 300mA load cur-

rent and ground-pin current is only 80A, making the

AAT2861 ideal for battery-operated applications.

The AAT2861 is available in a Pb-free, space-saving

TQFN34-24 package and operates over the -40°C to

+85°C ambient temperature range.

Features

• Input Voltage Range: 2.7V to 5.5V

• AS2Cwire Serial Interface

• Tri-Mode Charge Pump

 Drives up to Eight LEDs (Backlight/Flash)

• Programmable Backlight Current Settings

 31mA Maximum Current per Channel

 32 Linear Current Settings

 Independent Main/Sub Settings

 Programmable Fade-In and Fade-Out

• Programmable Flash Current

 600mA Total Flash Current

 16 Linear Current Settings

 1- or 2-Channel Configuration

• 1MHz Switching Frequency

• Automatic Soft-Start

• Three Linear Low Dropout Regulators

 300mA Output Current

 150mV Dropout

 Programmable Output Voltage from 1.2V to 3.3V

 Output Auto-Discharge for Fast Shutdown

• Built-In Thermal Protection

• Automatic Soft Start

• -40°C to +85°C Temperature Range

• TQFN34-24 Package

Applications

• Camera Enabled Mobile Devices

• Digital Still Cameras

• Multimedia Mobile Phones

Typical Application

CF1

1µF

CF2

1µF

C1+ C1- C2+ C2-

COUT

2.2µF

VOUT

OUT

BL1

BL2

BL3

BL4

BL7/FL2

VLDOA

at 300mA

LDOA

CLDOA

2.2µF

VBAT

3.6V AAT2861-x

AGND

BL5

BL6

EN/SETEN/SET

FL_EN

CIN

2.2µF

LDOB

CLDOB

2.2µF

LDOC

CLDOC

2.2µF

PGND

VLDOB

at 300mA

VLDOC

at 300mA

EN_ LDOAEN_ LDOA

EN_LDOB/CEN_ LDOB/C

WLEDs

OSRAM LW M673

or equivalent

Flash LEDs

Lumiled LXCL-PWF1

or equivalent

FL1

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Pin Descriptions

Pin # Symbol Description

1 OUT

Charge pump output. OUT is the output of the charge pump and supplies current to the backlight and ﬂ ash

LEDs. Connect the backlight and ﬂ ash LED anodes to OUT. Bypass OUT to PGND with a 2.2F or larger

ceramic capacitor as close to the AAT2861 as possible.

2 C2+ Positive terminal of charge pump capacitor 2. Connect the 1F charge pump capacitor 2 from C2+ to C2-.

3 EN/SET AS2Cwire serial input. EN/SET is the address and data input of the AS2Cwire serial interface. AS2Cwire is

used to control backlight, ﬂ ash and LDO functions.

4 FL_EN Flash enable. FL_EN is the enable control for the Flash LEDs. For the FL_EN pin to enable the ﬂ ash current,

the EN/SET pin must also be pulled high.

5 EN_LDOA LDO A enable pin. EN_LDOA turns on or off LDO regulator A. The EN/SET pin must also be pulled high for

LDO A to be enabled. The EN_LDOA input can be overwritten via the AS2Cwire interface to disable LDO A.

6 EN_LDOB/C

LDO B and LDO C enable pin. EN_LDOB/C enables both LDO regulators B and C. The EN/SET pin must

also be pulled high for the LDO regulators to be enabled. The EN_LDOB/C input can be overwritten via the

AS2Cwire interface to disable either LDO B or LDO C.

7 AGND Analog ground. Connect AGND to PGND at a single point as close to the AAT2861 as possible.

8 LDOC LDOC is the voltage output of LDO C. Bypass LDOC to AGND with a 2.2F or larger capacitor as close to

the AAT2861 as possible.

9 IN Input power pin for all three LDOs. Connect Pin 9 to Pin 23 with as short a PCB trace as practical.

10 LDOB LDOB is the voltage output of LDO B. Bypass LDOB to AGND with a 2.2F or greater capacitor as close to

the AAT2861 as possible.

11 LDOA LDOA is the voltage output of LDO A. Bypass LDOA to AGND with a 2.2F or larger ceramic capacitor as

close to the AAT2861 as possible.

12 BL1 Backlight LED 1 current sink. BL1 controls the current through backlight LED 1. Connect the cathode of

backlight LED 1 to BL1. If not used, connect BL1 to OUT.

13 BL2 Backlight LED 2 current sink. BL2 controls the current through backlight LED 2. Connect the cathode of

backlight LED 2 to BL2. If not used, connect BL2 to OUT.

14 BL3 Backlight LED 3 current sink. BL3 controls the current through backlight LED 3. Connect the cathode of

backlight LED 3 to BL3. If not used, connect BL3 to OUT.

15 BL4 Backlight LED 4 current sink. BL4 controls the current through backlight LED 4. Connect the cathode of

backlight LED 4 to BL4. If not used, connect BL4 to OUT.

16 BL5 Backlight LED 5 current sink. BL5 controls the current through backlight LED 5. Connect the cathode of

backlight LED 5 to BL5. If not used, connect BL5 to OUT.

17 BL6 Backlight LED 6 current sink. BL6 controls the current through backlight LED 6. Connect the cathode of

backlight LED 6 to BL6. If not used, connect BL6 to OUT.

18 BL7 (FL2)

AAT2861-1/3: Backlight LED 7 current sink. BL7 controls the current through backlight LED 7. Connect the

cathode of backlight LED 7 to BL7. If not used, connect BL7 to OUT.

AAT2861-2: Flash LED 2 current sink. FL2 controls the current through Flash LED 2. Connect the cathode

of Flash LED 2 to FL2. If not used, connect FL2 to OUT.

19 FL1 Flash LED 1 current sink. FL1 controls the current through Flash LED 1. Connect the cathode of Flash LED

1 to FL1. If not used, connect FL1 to OUT.

20 PGND Power ground. Connect PGND to AGND at a single point as close to the AAT2861 as possible.

21 C2- Negative terminal of charge pump capacitor 2.

22 C1- Negative terminal of charge pump capacitor 1.

23 IN Power input. Connect IN to the input source voltage. Bypass IN to PGND with a 2.2F or larger ceramic

capacitor as close to the AAT2861 as possible.

24 C1+ Positive terminal of charge pump capacitor 1. Connect the 1F charge pump capacitor 1 from C1+ to C1-.

EP Exposed paddle (bottom) Connect to PGND/AGND.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Pin Configuration

TQFN34-24

(Top View)

24 23 22 21 20

10 11 12

OUT

C2+

EN/SET

FL_EN

EN_LDOA

EN_LDOB/C

AGND

LDOC

LDOB

LDOA

BL1

BL5

BL6

BL4

BL3

BL2

BL7 (FL2)

FL1

PGND

C2-

C1-

C1+

Part Number Descriptions1

Part Number

Backlight LED Outputs

Flash LED OutputsMain Sub

AAT2861IMK-1-T1 4 3 1

AAT2861IMK-2-T1 4 2 2

AAT2861IMK-3-T1 5 2 1

Absolute Maximum Ratings2

Symbol Description Value Units

IN, OUT, BL1, BL2, BL3, BL4, BL5, BL6, BL7/FL2, FL1 Voltage to AGND -0.3 to 6.0 V

C1+, C2+ Voltage to AGND -0.3 to VOUT + 0.3 V

C1-, C2-, LDOA, LDOB, LDOC, EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Voltage to AGND -0.3 to VIN + 0.3 V

PGND Voltage to AGND -0.3 to 0.3 V

TJOperating Junction Temperature Range -40 to 150 °C

TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C

Thermal Information3,4

Symbol Description Value Units

PDMaximum Power Dissipation 2.0 W

JA Maximum Thermal Resistance 50 °C/W

1. Backlight and Flash Configuration within a part number is configured though the AS2Cwire serial interface. For example, disabling the “Main Equals Sub” feature (Address 8,

Data 5 - 8) in the AAT2861-1 will configure BL1-BL4 LED outputs as MAIN and BL5-BL7 outputs as SUB.

2. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions

specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.

3. Derate 20mW/°C above 25°C ambient temperature.

4. Mounted on a FR4 circuit board.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Electrical Characteristics1

VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =

25°C.

Symbol Description Conditions Min Typ Max Units

VIN IN Operating Voltage Range 2.7 5.5 V

IIN

IN Operating Current (1x mode, Main

Channels enabled, IBLX not included)

EN/SET = IN, BL1-BL7 = IN, FL_EN =

EN_LDOA = EN_LDOB/C = AGND 600 A

IN Operating Current (2x mode, Main

Channels enabled, IBLX not included)

2X Mode; EN/SET = IN, FL_EN = EN_LDOA =

EN_LDOB/C = AGND; BL1-BL7 = OPEN 5.5 mA

IN Operating Current (LDOA, LDOB and

LDOC enabled)

EN/SET = EN_LDOA = EN_LDOB/C = IN; FL_EN

= AGND; ADDR = 3; DATA = 1; No Load 225 A

IN Operating Current (Only LDOA

enabled)

EN/SET = EN_LDOA = IN; FL_EN = EN_LDOB/C

= AGND, ADDR = 3; DATA = 1; No Load 80 A

IIN(SHDN) IN Shutdown Current EN/SET, FL_EN, EN_LDOA, EN_LDOB/C = AGND 1.0 A

TSD Over-Temperature Shutdown Threshold 140 °C

TSD(HYS) Over-Temperature Shutdown Hysteresis 15 °C

Charge Pump Section

VOUT OUT Output Voltage 5.2 V

IOUT(MAX) OUT Maximum Output Current VIN = 3.0V, VOUT = 4.0 800 mA

VIN(TH_H, BL)

BL1-BL7 Charge Pump Mode Transition

Hysteresis

EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA

= 16; ADDR = 3, DATA = 3; ADDR = 2, DATA

= 12

0.3 V

VIN(TH_H, FL)

FL1-FL2 Charge Pump Mode Transition

Hysteresis

EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =

10, DATA = 1 1V

fOSC Charge Pump Oscillator Frequency TA = 25°C 1 MHz

tCP(SS) Charge Pump Soft-Start Time TA = 25°C 100 s

BL1-BL6, BL7/FL2, FL1 LED Drivers

IBLx BL1-BL7 Current Accuracy

EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA

= 16; ADDR = 3, DATA = 3; ADDR = 2, DATA

= 12

18 20 22 mA

IBL_x BL1-BL7 Current Accuracy

EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA

= 16; ADDR = 3, DATA = 4; ADDR = 2, DATA

= 14

1.6 2 2.4 mA

I(BLx)/

IBL(AVG)

BL1-BL7 Current Matching2

EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA

= 16; ADDR = 3, DATA = 3; ADDR = 2, DATA

= 12

VBL_(TH)

BL1-BL7 Charge Pump Transition

Threshold

EN/SET = IN; VIN – VF = 1V; ADDR=0, DATA =

16; ADDR = 3, DATA = 3; ADDR = 2, DATA =

0.2 V

tFADE

BL1-BL7 Automatic Fade-In/Fade-Out

Timer

EN/SET = IN; VIN – VF = 1V; ADDR = 0, DATA =

16; ADDR = 1, DATA = 1; ADDR = 2, DATA =

12; ADDR = 3, DATA = 3

0.75 1 1.25 s

IFL[1] FL1 Current Accuracy EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =

10, DATA = 1 540 600 660 mA

IFL[1](DATA13) FL1 Current Accuracy EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =

10, DATA = 13 108 120 132 mA

I(FLx)/

IFL(AVG)

FL1-FL2 Current Matching (AAT2861-2

only)

EN/SET = FL_EN = IN; VIN – VF = 1V, ADDR =

10, DATA = 1 5%

VFL[1/2](TH) FL1 Charge Pump Transition Threshold EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =

10, DATA = 1 0.45 V

tFL/tFL_SET Flash Safety Timer Period EN/SET = FL_EN = IN; VIN – VF = 1V; ADDR =

11, DATA = 1 1.5 2 2.5 s

1. The AAT2861 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-

tion with statistical process controls.

2. Current matching is defined as the deviation of any sink current from the average of all active channels.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Electrical Characteristics (continued)1

VIN = 3.6V; CIN = COUT = 2.2F; C1 = C2 = 1F; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA =

25°C.

Symbol Description Conditions Min Typ Max Units

Linear Regulators

VLDO[A/B/C]/

VLDO[A/B/C]

LDOA, LDOB, LDOC Output Voltage Tolerance

ILDO = 1mA to 200mA; TA = 25°C -1.5 1.5 %

ILDO = 1mA to 200mA;

TA = -40°C to +85°C -3.0 3.0 %

ILDO[A/B/C](MAX) LDOA, LDOB, LDOC Load Current 200 mA

VLDO[A/B/C](DO) LDOA, LDOB, LDOC Dropout Voltage2VLDO[A/B/C]  3.0V; ILDO = 150mA 75 150 mV

VLDO/

VLDO*VIN

LDOA, LDOB, LDOC Line Regulation VIN = (VLDO[A/B/C] + 1V) to 5V 0.09 %/V

PSRR[A/B/C] LDOA, LDOB, LDOC Power Supply Rejection Ratio ILDO[A/B/C] = 10mA, 1kHz 50 dB

ROUT_(DCHG) LDOA, LDOB, LDOC Auto-Discharge Resistance 20 

EN/SET AS2Cwire and Logic Control

VIH

EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input High

Threshold Voltage 2.7V  VIN  5.5V 1.4 V

VIL

EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input Low

Threshold Voltage 2.7V  VIN  5.5V 0.4 V

IIN(LKG)

EN/SET, FL_EN, EN_LDOA, EN_LDOB/C Input Leak-

age Current EN/SET = IN = 5V -1 1 A

tEN/SET(OFF) EN/SET Input OFF Timeout 500 s

tEN/SET(LAT) EN/SET Input Latch Timeout 500 s

tEN/SET(LOW) EN/SET Input LOW Time 0.3 75 s

tENSET(H-MIN) EN/SET Minimum High Time 50 ns

tENSET(H-MAX) EN/SET Maximum High Time 75 s

1. The AAT2861 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-

tion with statistical process controls.

2. VDO[A/B/C] is defined as VIN – LDO[A/B/C] when LDO[A/B/C] is 98% of nominal.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Typical Characteristics

Backlight Efficiency vs. Input Voltage

Input Voltage (V)

Efficiency (%)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

100

30mA/ch, VF = 3.95V

15mA/ch, VF = 3.5V

4.2mA/ch, VF = 3.4V

Flash Efficiency vs. Input Voltage

Input Voltage (V)

Efficiency (%)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

100

320mA/ch, VF = 3.25V

160mA/ch, VF = 3.15V

Backlight Current Matching vs. Temperature

(VIN = 3.6V; 20mA/ch)

Temperature (°C)

Backlight Output Current (mA)

-40 -15 10 35 60 85

Channel 1 - Channel 6/7

Charge Pump Output Turn On Characteristic

(VIN = 3.6V; 0mA/ch; COUT = 2.2µF)

Time (50µs/div)

VEN/SET (top) (V)

Output Voltage (bottom) (V)

0.0

2.0

4.0

0.0

1.0

2.0

3.0

4.0

Turn On to 1X Mode Flash

(VIN = 4.2V; 300mA/ch)

Time (50µs/div)

VFL_EN

(2V/div)

VOUT

(2V/div)

IIN

(200mA/div)

VFLX

(2V/div) 0

200

400

600

Turn On to 1.5X Mode Flash

(VIN = 3.6V; 300mA/ch)

Time (50µs/div)

VFL_EN

(2V/div)

VOUT

(2V/div)

IIN

(200mA/div)

VFLX

(2V/div) 0

200

400

600

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Typical Characteristics

Turn On to 2X Mode Flash

(VIN = 2.8V; 300mA/ch)

Time (50µs/div)

VFL_EN

(2V/div)

VOUT

(2V/div)

IIN

(200mA/div)

VFLX

(2V/div) 0

200

400

600

Turn On to 1X Mode Backlight

(VIN = 3.6V; 20mA/ch)

Time (200µs/div)

VEN/SET

(2V/div)

VOUT

(2V/div)

IIN

(100mA/div)

VSINK

(2V/div)

Turn On to 1.5X Mode Backlight

(VIN = 3.2V; 20mA/ch)

Time (200µs/div)

VEN/SET

(2V/div)

VOUT

(2V/div)

IIN

(200mA/div)

VSINK

(2V/div) 0V

Turn On to 2X Mode Backlight

(VIN = 3.0V; 20mA/ch)

Time (200µs/div)

VEN/SET

(2V/div)

VOUT

(2V/div)

IIN

(200mA/div)

VSINK

(2V/div)

Turn Off from 1.5X Mode Backlight

(VIN = 3.2V; 20mA/ch)

Time (200µs/div)

VEN/SET

(2V/div)

VDIODE

(2V/div)

IIN

(200mA/div)

Operating Characteristic

(VIN = 3.2V; 20mA/ch Backlight; 1.5x Mode; COUT = 2.2µF)

Time (500ns/div)

Input Voltage (AC coupled)

(top) (mV)

Charge Pump

Out

put Voltage

(AC coupled) (bottom) (mV)

-50

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Typical Characteristics

Operating Characteristic

(VIN = 3.0V; 20mA/ch Backlight; 2X Mode; COUT = 2.2µF)

Time (500ns/div)

Input Voltage (AC coupled)

(top) (mV)

Charge Pump

Out

put Voltage

(AC coupled) (bottom) (mV)

-20

-10

LDO A/B/C Load Regulation

(VIN = 3.6V)

Load Current (mA)

LDO Output Voltage Deviatoin (%)

0.1 1 10 100 1000

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

VOUT = 1.8V

VOUT = 3.0V

LDO A/B/C Output Voltage vs. Temperature

(VIN = 3.6V; ILDO = 0mA)

Temperature (°C)

LDO Output Voltage Deviatoin (%)

-40 -15 10 35 60 85

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

VOUT = 1.8V

VOUT = 3.3V

LDO A/B/C Load Transient Response

(

ILDO =

10mA to 200mA;

VIN =

3.6V;

VLDO =

1.8V;

CLDO =

2.2µF)

Time (20µs/div)

LDO Output Current

(top) (mA)

LDO Output Voltage

(bottom) (V)

-500

-400

-300

-200

-100

100

200

1.60

1.70

1.80

1.90

2.00

LDO A/B/C Line Transient Response

(VIN = 3.6V to 4.2V; ILDO = 10mA; VOUT = 1.8V; CLDO = 2.2µF)

Time (1ms/div)

Input Voltage

(top) (V)

LDO Output Voltage

(bottom) (V)

3.6

4.0

4.4

1.78

1.79

1.80

1.81

1.82

LDO A/B/C Turn On Characteristic

(VLDO = 1.8V; VIN = 3.6V; CLDO = 2.2µF)

Time (20µs/div)

VENLDOX (top) (V)

LDO Output (bottom) (V)

0.0

2.0

4.0

0.0

0.5

1.0

1.5

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Typical Characteristics

EN/SET, FL_EN, EN_LDOA, EN_LDOB/C

High Threshold Voltage vs. Input Voltage

Input Voltage (V)

VEN/SET(H), VFL_EN(H),

VEN_LDOA(H), VEN_LDOB/C(H) (V)

2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

-40°C

25°C

85°C

EN/SET, FL_EN, EN_LDOA, EN_LDOB/C

Low Threshold Voltage vs. Input Voltage

Input Voltage (V)

VEN/SET(L), VFL_EN(L),

VEN_LDOA(L), VEN_LDOB/C(L) (V)

2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

-40°C

25°C

85°C

EN/SET Input Latch Timeout vs. Input Voltage

Input Voltage (V)

TLAT (µs)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

100

150

200

250

300

350

400

-40°C

25°C

85°C

EN/SET Input Off Timeout vs. Input Voltage

Input Voltage (V)

TOFF (µs)

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

100

150

200

250

300

350

400

450

500

-40°C

25°C

85°C

AAT2861

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Functional Block Diagrams

AAT2861IMK-1-T1

BL5

C1-

C1+

C2-

C2+

LDOA

OUT

BL1

BL2

BL3

BL4

BL6

BL7

AGND

EN_LDOA

LDOB

LDOC

EN_LDOB/C

EN/SET

FL_EN

PGND

REF

FL1

1x/1.5x/2x

Tri-mode

Charge Pump

Control

Logic

Main

Backlight

Current

Control

Sub

Backlight

Current

Control

Flash

Control

AAT2861

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AAT2861IMK-2-T1

BL5

1x/1.5x/2x

Tri-mode

Charge Pump

C1-

C1+

C2-

C2+

LDOA

OUT

BL1

BL2

BL3

BL4

BL6

Control

Logic

FL2

AGND

EN_LDOA

LDOB

LDOC

EN_LDOB/C

EN/SET

FL_EN

PGND

REF

FL1

Flash

Control

Sub

Backlight

Current

Control

Main

Backlight

Current

Control

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

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AAT2861IMK-3-T1

BL5

1x/1.5x/2x

Tri-mode

Charge Pump

C1-

C1+

C2-

C2+

LDOA

OUT

BL1

BL2

BL3

BL4

BL6

Control

Logic

BL7

AGND

EN_LDOA

LDOB

LDOC

EN_LDOB/C

EN/SET

FL_EN

PGND

REF

FL1

Flash

Control

Sub

Backlight

Current

Control

Main

Backlight

Current

Control

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

202070A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 15, 2012

Functional Description

The AAT2861 is a highly integrated backlight and photo-

flash driver family with three LDO regulators. The charge

pump LED driver powers the backlight and flash LEDs

from the 2.7V to 5.5V input voltage. The LDO regulators

are powered from the same input and produce regulated

output voltage between 1.2V and 3.3V. Control of the

LEDs and the LDO output voltage is through an AS2Cwire

serial interface for easy programming.

LED Drivers

The AAT2861 drives six or seven backlight LEDs up to

31mA each and a total of 600mA flash current through

one or two channels. The LEDs are driven from a charge

pump to insure that constant current is maintained over

the entire battery voltage range. The charge pump auto-

matically switches from 1X, to 1.5X, to 2X modes and

back to maintain the LED current while minimizing

power loss for high efficiency. The charge pump operates

at the high 1MHz switching frequency, allowing the use

of small 1F ceramic capacitors.

Each individual LED is driven by a current sink to GND,

allowing individual current control with high accuracy

over a wide range of input voltages and LED forward

voltages while maintaining high efficiency.

The charge pump is controlled by the voltage across the

LED current sinks. When any one of the active backlight

current sink/channel voltages drops below 200mV or the

flash current sink/channel drops below 450mV, the

charge pump goes to the next higher mode (from 1X to

1.5X or from 1.5X to 2X mode) to maintain sufficient

LED voltage for constant LED current. The AAT2861 con-

tinuously monitors the LED forward voltages and uses

the input voltage to determine when to reduce the

charge pump mode for better efficiency. There is also a

300mV mode-transition hysteresis that prevents the

charge pump from oscillating between modes.

LED Current Control

Both the backlight and flash LED currents are controlled

through the AS2Cwire serial interface. The backlight LED

current can be set between 0.5mA and 31mA in approx-

imately 1mA steps while the flash LED current can be set

between 0 and 600mA in 40mA steps or 0 to 300mA in

20mA steps for two channel flash version. The backlight

LED currents match to within 3% while the flash LED

currents match to within 5%.

To eliminate the latency of the AS2Cwire serial interface,

the flash LED is enabled through a dedicated input,

FL_EN. The AAT2861 also includes a safety timer that

prevents thermal overstress of the flash LED(s). This is

important because many flash LEDs operate for a brief

period beyond their steady-state operating limitations.

If the flash driving hardware and/or software fail to turn

the LED off, the safety timer insures that the LED or

other circuitry is not damaged.

Both the backlight and flash LED currents are pro-

grammed through the AS2Cwire serial interface as are

the backlight fade-in/fade-out timer and the flash safety

timer. See the “AS2Cwire Serial Interface Programming”

section of this datasheet for more information on setting

the LED currents.

LDO Regulators

The AAT2861 includes three low dropout (LDO) linear

regulators. These regulators are powered from the bat-

tery and produce a fixed output voltage set through the

AS2Cwire serial interface. The output voltage can be set

to one of 16 output voltages between 1.2V and 3.3V. The

LDO regulators can be turned on/off with the external

enable pins EN_LDOA and EN_LDOB/C. Additionally, the

AS2Cwire interface allows the LDO regulators to be

enabled independently when the EN_LDOA and EN_

LDOB/C pins are pulled high.

The LDO regulators require only a small 2.2F ceramic

output capacitor for stability. If improved load transient

response is required, larger-valued capacitors can be

used without stability degradation.

AS2Cwire Serial Interface Protocol

The AAT2861 is dynamically programmable by the

AS2Cwire single-wire interface. AS2Cwire records rising

edges detected at the EN/SET pin to address and load

the data registers. The timing diagram in Figure 1 shows

the typical transmission protocol.

AAT2861

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Address Data

EN/SET

217 18

Address

Data Reg 1

Data Reg 2

12 . . . n <= 16

LAT

Figure 1: AS2Cwire Serial Interface Timing Diagram.

AS2Cwire latches data or address after the EN/SET input

has been held high for time tLAT (500s). Address or data

is differentiated by the number of EN/SET rising edges.

Since the data registers are 4 bits each, the differentiating

number of pulses is 24 or 16, so that Address 0 is identi-

fied by 17 rising edges, Address 1 by 18 rising edges,

Address 2 by 19 rising edges, etc. Data is set to any num-

ber of rising edges between 1 and 16. A typical write

protocol is a burst of EN/SET rising edges identifying a

particular address, followed by a pause with EN/SET held

high for the tLAT timeout period, then a burst of rising

edges signifying data, and another tLAT timeout after the

data has been sent. Once an address is set, multiple

writes to that address are allowed since the address is not

reset after each write. Address edges are needed when

changing the address, or writing to an address other than

the default after shutdown. Address 0 is the default

address after shutdown. If the part is enabled with only

data edges and no address, then Address 0 will be pro-

grammed and LED Backlight channels BL1-BL7 will be

enabled according to the number of data edges applied.

When EN/SET is held low for a time longer than tOFF

(500s), the AAT2861 enters shutdown mode and draws

less than 1A of current from IN. At shutdown, the data

and address registers are reset to 0.

AS2Cwire Serial Interface Programming

The AAT2861’s AS2Cwire programmable Address regis-

ters are listed in Table 1. There are 14 Address registers,

four registers control the three LDOs, six control the

backlight LED configuration, two control the flash/lamp

LED configuration and two are used to individually dis-

able each backlight or flash channel.

Backlight Current Control (Address 0)

Address 0 controls the enabling of the Main and Sub

channels. Table 2 shows the Data Codes used to control

the Main and Sub Channels independently. The default

condition for all backlight outputs (BL1-BL7) is OFF after

power-up.

The AAT2861 family of LMUs also provides an internal LED

current fade-in, fade-out feature. This feature is useful in

those applications where it is preferred to turn on and off

the backlight current using a smooth transition versus an

abrupt transition. During the fade-in cycle, the LED cur-

rent will be slowly increased to the programmed current

level (set in Addresses 2 to 5). During the fade-out cycle,

the LED current will be decreased linearly down to its

programmed fade-out current threshold (set by Address

1) at which point the BL channels will be turned off. The

fade-in and fade-out current is a linear transition over a

time period of approximately 1 second.

The fade-in and fade-out function can be enabled and

disabled independently for the Main and Sub groups by

writing the desired Data to Address 0. Table 2 also lists

the data codes used to program enable and disable the

fade functions for the main and sub channels. If the

“Main Equals Sub” feature (Address 3) is enabled

(MEQS=1), the fade-in and fade-out settings for the Main

and Sub channels are controlled by the “Main Fade” set-

ting and the “Sub Fade” bit in Address 1 will be ignored.

At startup when the EN/SET pin is first pulled high,

Address 0 is the default active register. The main and

sub channels can be turned on by immediately writing

data. For example, if Data = 4 is written the main and

sub channels will turn on to the default value of 19mA.

AAT2861

DATA SHEET

Backlight/Flash LED Driver and Multiple LDO Lighting Management Unit

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Data Sub

Fade On Main

Fade On Sub

Channel Main

Channel

1* No* No* Off* Off*

2 No No Off On

3 No No On Off

4NoNoOnOn

5 No Yes Off Off

6 No Yes Off On

7 No Yes On Off

8 No Yes On On

9 Yes No Off Off

10 Yes No Off On

11 Yes No On Off

12 Yes No On On

13 Yes Yes Off Off

14 Yes Yes Off On

15 Yes Yes On Off

16 Yes Yes On On

Table 2: Backlight Main/Sub ON/OFF and Fade

Enable (Address 0).

Backlight Fade-In and Fade-Out Control

(Address 1)

During the fade-out cycle, the LED current will be

decreased linearly down to its programmed fade-out

current threshold (set by Address 1) at which point the

BL channels will be turned off. The default fade-out cur-

rent level is 500A, but can be changed to 1mA, 2mA or

3mA using the data codes listed in Table 3.

Data Fade Out Current Level (mA)

1* 0.50*

2 1.0

3 2.0

4 3.0

Table 3: Backlight Fade-In and Fade-Out Control

(Address 1).

Backlight Current Control (Addresses 2 to 5)

The AAT2861’s AS2Cwire Addresses 2, 3, 4, and 5 control

the backlight LED output current level in Main and Sub

group of outputs. Address 2 and Address 3 control the

Main backlight channel current to one of 32 levels

according to Table 4 below. Address 3 acts as the MSB

and Address 2 acts as the LSB for the current level

setup. Address 4 and Address 5 control the Sub back-

light channels current to one of 32 levels according to

Table 5 below.

*Denotes the default (power-on-reset) value

Address EN/SET

Rising Edges Function D3 D2 D1 D0

0 17 Backlight Main/Sub ON/OFF and Fade Enable FADE_SUB FADE_MAIN SUB_ON MAIN_ON

1 18 Backlight Fade Control X X FLOOR[1] FLOOR[0]

2 19 Backlight Current Main, LSB's BLM[3] BLM[2] BLM[1] BLM[0]

3 20 Backlight Current Main, MSB Reserved X MEQS BLM[4]

4 21 Backlight Current Sub, LSB's BLS[3] BLS[2] BLS[1] BLS[0]

5 22 Backlight Current Sub, MSB X X X BLS[4]

6 23 LDO Disable Control X OFF_LDOC OFF_LDOB OFF_LDOA

7 24 LDO A Output Voltage Control LDOA[3] LDOA[2] LDOA[1] LDOA[0]

8 25 LDO B Output Voltage Control LDOB[3] LDOB[2] LDOB[1] LDOB[0]

9 26 LDO C Output Voltage Control LDOC[3] LDOC[2] LDOC[1] LDOC[0]

10 27 Flash Current F_HI[3] F_HI[2] F_HI[1] F_HI[0]

11 28 Flash Timer Control X X F_TIME[1] F_TIME[0]

12 29 LED Channel Disable Control (BL1 – BL4) OFF_BL4 OFF_ BL3 OFF_ BL2 OFF_ BL1

13 30 LED Channel Disable Control (BL5, BL6,

BL7/FL2, FL1) OFF_FL1 OFF_BL7/FL2 OFF_BL6 OFF_BL5

Table 1: AAT2861- 1 Configuration/Control Register Allocation

(* signifies that the data bit has a POR default bit value = 1; X signifies “Don’t care”).

AAT2861

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Main Equals Sub OFF (MEQS=0) Main Equals Sub ON (MEQS=1)

Address Data Address Data Main Current Address Data Address Data Main Current

3121 31 3321 31

3122 30 3322 30

3123 29 3323 29

3124 28 3324 28

3125 27 3325 27

3126 26 3326 26

3127 25 3327 25

3128 24 3328 24

3129 23 3329 23

3 1 2 10 22 3 3 2 10 22

3 1 2 11 21 3 3 2 11 21

3 1* 2 12* 20* 3 3 2 12 20

3 1 2 13 19 3 3 2 13 19

3 1 2 14 18 3 3 2 14 18

3 1 2 15 17 3 3 2 15 17

3 1 2 16 16 3 3 2 16 16

3221 15 3421 15

3222 14 3422 14

3223 13 3423 13

3224 12 3424 12

3225 11 3425 11

3226 10 3426 10

3227 9 3427 9

3228 8 3428 8

3229 7 3429 7

32210 6 34210 6

32211 5 34211 5

32212 4 34212 4

32213 3 34213 3

32214 2 34214 2

32215 1 34215 1

3 2 2 16 0.5 3 4 2 16 0.5

Table 4: Backlight Main Current Control (Addresses 2 and 3).

AAT2861

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Sub Backlight

Address Data Address Data Sub Current

5141 31

5142 30

5143 29

5144 28

5145 27

5146 26

5147 25

5148 24

5149 23

51410 22

51411 21

5 1* 4 12* 20*

51413 19

51414 18

51415 17

51416 16

5241 15

5242 14

5243 13

5244 12

5245 11

5246 10

5247 9

5248 8

5249 7

52410 6

52411 5

52412 4

52413 3

52414 2

52415 1

5 2 4 16 0.5

Table 5: Backlight Sub Current Control

(Addresses 4 and 5).

The current settings for the Main and Sub channels are

each divided into two Addresses. Any change in Data to

the “Backlight Current Main (or Sub), LSB’s” Address will

result in an immediate change to the LED current output

level. Programming new current settings that require a

change to both “Backlight Current Main (or Sub), MSB”

and “Backlight Current Main (or Sub), LSB’s” Addresses

could result in an errant intermediate current setting. To

avoid this problem when the Data in “Backlight Current

Main (or Sub), MSB” Address is changed the new current

setting will not take effect until “Backlight Current Main

(or Sub), LSB’s” Address has been written to and

latched.

For example, a change from 28mA to 8mA in the Main

backlight channels should follow this procedure. First,

28mA is set by programming Data = 3 to Address 2 and

Data=1 to Address 3. When changing to 8mA first write

Data=2 to Address 3. The current level will not change

after this step. Then write Data=7 to Address 2. After

Address 2 has been latched the new 8mA current level

will be set.

Address 3 also controls the “Main Equals Sub” feature in

the AAT2861 products. This feature allows all backlight

channels to be controlled with only the Main Channel

current settings. If the “Main Equals Sub” feature is

turned on (Data 3, or 4 in Address 3) the current set-

tings of the Sub Channel are ignored. All backlight chan-

nels will be set to the same current levels as determined

by the Data programmed to “Backlight Current Main” in

Addresses 2 and 3. The Main and Sub channels are

turned on and off by the “Main On” setting in Address 0.

The default condition is for the “Main Equals Sub” feature

to be turned OFF (MEQS=0) after power-up.

Table 6 shows the Main and Sub Channel Configurations

for the three versions of the AAT2861. The effect of the

“Main Equals Sub” feature is clearly represented in this

table.

Part Number

Main Equals Sub (IMAIN = ISUB)

Yes (Default) No

AAT2861-1 7M+0S+1FL 4M+3S+1FL

AAT2861-2 6M+0S+2FL 4M+2S+2FL

AAT2861-3 7M+0S+1FL 5M+2S+1FL

Table 6: Main and Sub Channel Configurations.

LDO Output Voltage Control

(Addresses 6 to 9)

The AAT2861’s three LDO regulators are configured by

programming Addresses 6, 7, 8, and 9 via the AS2Cwire

interface. With the EN/SET pin pulled high and the

AAT2861 turned on, LDOA can be enabled using the EN_

LDOA pin. LDOB and LDOC can be enabled together using

the EN_LDOB/C pin. Additional LDO regulator control can

be achieved using Address 6 to override the enable com-

mand of the EN_LDOA and EN_LDOB/C pins. For example,

with the EN_LDOA and EN_LDOB/C pins enabled, writing

Data 5 to Address 6 will disable LDOB and leave LDOA and

LDOC enabled. Table 7 shows the LDO disable control.

Writing data to Addresses 7, 8, and 9 set the output volt-

ages for LDOA, LDOB, and LDOC to one of 16 levels. The

available LDO output voltages are shown in Table 8.

AAT2861

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Data LDO C LDO B LDO A

1* Controlled by

EN_LDOB/C*

Controlled by

EN_LDOB/C*

Controlled by

EN_LDOA*

2Controlled by

EN_LDOB/C

Controlled by

EN_LDOB/C OFF

3Controlled by

EN_LDOB/C OFF Controlled by

EN_LDOA

4Controlled by

EN_LDOB/C OFF OFF

5 OFF Controlled by

EN_LDOB/C

Controlled by

EN_LDOA

6 OFF Controlled by

EN_LDOB/C OFF

7 OFF OFF Controlled by

EN_LDOA

8 OFF OFF OFF

Table 7: LDO Disable Control (Address 6).

Data VLDOA (V) VLDOB (V) VLDOC (V)

1 1.2 1.2 1.2

2 1.3 1.3 1.3

3 1.5 1.5 1.5

4 1.6 1.6 1.6

5* 1.8* 1.8* 1.8*

6222

7 2.2 2.2 2.2

8 2.5 2.5 2.5

9 2.6 2.6 2.6

10 2.7 2.7 2.7

11 2.8 2.8 2.8

12 2.9 2.9 2.9

13333

14 3.1 3.1 3.1

15 3.2 3.2 3.2

16 3.3 3.3 3.3

Table 8: LDO X Output Voltage

(Addresses 7, 8, and 9).

Fast turn-off response time is achieved by an active out-

put pull-down circuit, which is enabled when the LDO

regulator is disabled.

Flash Driver Control (Address 10 and 11)

The AAT2861-1 and AAT2861-3 are both configured with

a single 600mA LED Flash channel, while the AAT2861-2

is configured with two LED Flash channels each capable

of driving 300mA per channel. Address 10 programs the

flash current level. Table 9 lists the data codes for the

programming Address 10. Upon startup, the power-on-

reset value in Address 10 is set to data code 13.

Data

Flash Current (mA) per Output

AAT2861-1 or -3 AAT2861-2

1 600 300

2 560 280

3 520 260

4 480 240

5 440 220

6 400 200

7 360 180

8 320 160

9 280 140

10 240 120

11 200 100

12 160 80

13* 120* 60*

14 80 40

15 40 20

16 OFF OFF

Table 9: Flash Current Level (Address 10).

Once the EN/SET pin is pulled high and the AAT2861 has

turned on, the LED Flash channels can be enabled by

pulling the FL_EN to IN. The current setting of the LED

Flash channels can be changed prior to enabling the

flash current, or while the flash current is on.

The LED Flash controller also comes with a safety timer

to prevent excessive heat generation and power loss

from extended high current power dissipation. The LED

flash safety timer duration can be set to four values by

writing to Address 11. The default value at startup is 2

seconds. Table 10 shows the Data Codes for the flash

safety timer.

*Denotes default (power-on-reset) value.

AAT2861

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Torch/movie mode is automatically entered when the

flash current setting is programmed to 120mA (60mA for

channel for the AAT2861-2) or lower with Data = 13, 14,

or 15. At these current levels the safety timer is auto-

matically disabled and the flash channels will remain on

as long as the FL_EN pin remains active. Extended dura-

tion flash use can be achieved for higher current settings

by writing Data 4 to Address 11 to disable the safety

timer. Though the AAT2861 includes an internal thermal

limit circuit, be careful to limit the current setting (Address

10) to a value that will not generate excessive heat which

may damage the flash LEDs or external circuitry.

Data Flash Time (sec)

1* 2*

3 0.5

4 Always ON

Table 10: Flash Safety Timer (Address 11).

LED Channel Disable Control

(Address 12 and 13)

Addresses 12 and 13 allow for additional programming

flexibility by allowing each LED channel to be indepen-

dently disabled. Normally, the backlight channels are

controlled by MAIN_ON and SUB_ON controls in Address

0, while the FL_EN pin turns on the flash channels.

Writing to Addresses 12 and 13 can override these con-

trols to allow for any combination of LEDs to be turned

on. The default state is for all LED channels to be

“Conditionally ON” to allow the normal enable control.

In the following example we see how to turn on BL1,

BL2, BL6, and BL7 in the AAT2861-1 (4M+3S+1FL). First

write Address 12, Data=13 and Address 13, Data=10 to

disable BL3, BL4, BL5, FL1. Then program the desired

current setting using Addresses 2 through 5. Finally,

write Address 0, Data=4.

(NOTE: ”Conditionally ON” state allows the LED channel

to be turned ON but does not turn the channel ON. For

BL1 to be enabled Data=2, 4, 6, 8… must be written to

Address 0, and Data=1, 3, 5, 7… must be written to

Address 12.)

*Denotes default (power-on-reset) value.

Data BL4 BL3 BL2 BL1

1* Conditionally ON* Conditionally ON* Conditionally ON* Conditionally ON*

2 Conditionally ON Conditionally ON Conditionally ON OFF

3 Conditionally ON Conditionally ON OFF Conditionally ON

4 Conditionally ON Conditionally ON OFF OFF

5 Conditionally ON OFF Conditionally ON Conditionally ON

6 Conditionally ON OFF Conditionally ON OFF

7 Conditionally ON OFF OFF Conditionally ON

8 Conditionally ON OFF OFF OFF

9 OFF Conditionally ON Conditionally ON Conditionally ON

10 OFF Conditionally ON Conditionally ON OFF

11 OFF Conditionally ON OFF Conditionally ON

12 OFF Conditionally ON OFF OFF

13 OFF OFF Conditionally ON Conditionally ON

14 OFF OFF Conditionally ON OFF

15 OFF OFF OFF Conditionally ON

16 OFF OFF OFF OFF

Table 11: LED Channel Individual Disable Control, BL1-BL4 (Address 12).

AAT2861

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Applications Information

LED Selection

The AAT2861 is specifically intended for driving white

LEDs. However, the device design will allow the AAT2861

to drive most types of LEDs with forward voltage speci-

fications ranging from 2.0V to 4.7V. LED applications

may include mixed arrangements for display backlight-

ing, color (RGB) LEDs, infrared (IR) diodes and any

other load needing a constant current source generated

from a varying input voltage. Since the BL1 to BL6, BL7/

FL2 and FL1 constant current sinks are matched with

negligible voltage dependence, the constant current

channels will be matched regardless of the specific LED

forward voltage (VF) levels.

The low-dropout current sinks in the AAT2861 maximize

performance and make it capable of driving LEDs with

high forward voltages. Multiple channels can be com-

bined to obtain a higher LED drive current without com-

plication.

Device Switching Noise Performance

The AAT2861 operates at a fixed frequency of approxi-

mately 1MHz to control noise and limit harmonics that

can interfere with the RF operation of cellular telephone

handsets or other communication devices. Back-injected

noise appearing on the input pin of the charge pump is

20mV peak-to-peak, typically ten times less than induc-

tor-based DC/DC boost converter white LED backlight

solutions. The AAT2861 soft-start feature prevents noise

transient effects associated with in-rush currents during

the start up of the charge pump circuit.

Device Power Efficiency

Charge-pump efficiency discussion in the following sec-

tions accounts only for the efficiency of the charge pump

section itself. Due to the unique circuit architecture and

design of the AAT2861, it is very difficult to measure

efficiency in terms of a percent value comparing input

power over output power.

Data FL1 BL7/FL2 BL6 BL5

1* Conditionally ON* Conditionally ON * Conditionally ON* Conditionally ON*

2 Conditionally ON Conditionally ON Conditionally ON OFF

3 Conditionally ON Conditionally ON OFF Conditionally ON

4 Conditionally ON Conditionally ON OFF OFF

5 Conditionally ON OFF Conditionally ON Conditionally ON

6 Conditionally ON OFF Conditionally ON OFF

7 Conditionally ON OFF OFF Conditionally ON

8 Conditionally ON OFF OFF OFF

9 OFF Conditionally ON Conditionally ON Conditionally ON

10 OFF Conditionally ON Conditionally ON OFF

11 OFF Conditionally ON OFF Conditionally ON

12 OFF Conditionally ON OFF OFF

13 OFF OFF Conditionally ON Conditionally ON

14 OFF OFF Conditionally ON OFF

15 OFF OFF OFF Conditionally ON

16 OFF OFF OFF OFF

Table 12: LED Channel Individual Disable Control, BL5, BL6, BL7/FL2, FL1 (Address 13).

*Denotes default (power-on-reset) value.

AAT2861

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Since the AAT2861 outputs are pure constant current

sinks and typically drive individual loads, it is difficult to

measure the output voltage for a given output (BL1 to

BL6, BL7/FL2, and FL1) to derive an overall output power

measurement. For any given application, white LED for-

ward voltage levels can differ, yet the output drive cur-

rent will be maintained as a constant.

This makes quantifying output power a difficult task

when taken in the context of comparing to other white

LED driver circuit topologies. A better way to quantify

total device efficiency is to observe the total input power

to the device for a given LED current drive level. The

best white LED driver for a given application should be

based on trade-offs of size, external component count,

reliability, operating range and total energy usage...not

just "% efficiency."

The AAT2861 efficiency may be quantified under very

specific conditions and is dependant upon the input volt-

age versus the output voltage seen across the loads

applied to outputs BL1 through BL6, BL7/FL2 or FL1 for

a given constant current setting. Depending on the com-

bination of IN and voltages sensed at the current sinks,

the device will operate in "Load Switch" (1X) mode.

When any one of the voltages sensed at the current

sinks nears dropout the device will operate in 1.5X or 2X

charge pump mode. Each of these modes will yield dif-

ferent efficiency values. One should refer to the following

two sections for explanations for each operational

mode.

AAT2861 charge pump conversion efficiency is defined

as the power delivered to the white LED load divided by

the input power:

η = =

PLEDs

VLED1 · ILED1 + ... + VLEDX · ILEDX

VIN · IIN

VLEDX = White LED Forward Voltage (VF)

ILEDX = White LED Bias Current (ID)

X = Number of White LEDs

The expression to define the estimated ideal efficiency

() for the AAT2861 in 1X mode is as follows:

η = =

PLEDs

X · VLEDX · ILEDX

VIN · IIN

X = 1, 2, 3, ..., 6 or 7 and IIN = X · ILEDX

η =

VLEDX

VIN

The AAT2861 charge pump is a fractional charge pump

which will boost the input supply voltage in the event

where IN is less then the required output voltage across

the backlight white LED load. The efficiency can be sim-

ply defined as a linear voltage regulator with an effective

white LED forward voltage that is equal to one and a half

(1.5x mode) times the input voltage.

With an ideal 1.5x charge pump, the input current is

1.5x of the output current. The expression to define the

estimated ideal efficiency () for the AAT2861 in 1.5x

mode is as follows:

η = =

PLEDs

VLED1 · ILED1 + ... + VLEDX · ILEDX

VIN · IIN

η = ; X = 1, 2, 3, ..., 6 or 7 and IIN = 1.5(X · ILEDX)

η =

X · VLEDX · ILEDX

VIN · IIN

VLEDX

1.5VIN

The same calculations apply for the AAT2861 in 2x mode

where for an ideal 2x charge pump, the input current is

2x of the output current. The expression for the esti-

mated ideal efficiency () for the AAT2861 in 2x mode is

as follows:

η = =

PLEDs

VLED1 · ILED1 + ... + VLEDX · ILEDX

VIN · IIN

η = ; X = 1, 2, 3, ..., 6 or 7 and IIN = 2(X · ILEDX)

η =

X · VLEDX · ILEDX

VIN · IIN

VLEDX

2VIN

In addition, with an ideal 1.5x charge pump, the output

current may be expressed as 2/3 of the input current.

For a charge pump with an output of 5V and a nominal

input of 3.5V, the theoretical efficiency is 95%. Due to

internal switching losses and IC quiescent current con-

sumption, the actual efficiency can be measured at 93%.

Efficiency will decrease substantially as load current

drops below 1mA or when the level of IN approaches

OUT. The same calculations apply for 2X mode where the

output current then becomes 1/2 of the input current.

Capacitor Selection

Careful selection of all external capacitors CIN, C1, C2,

CLDO(A/B/C), and COUT is important because they will affect

turn-on time, output ripple and transient performance.

Optimum performance will be obtained when low ESR

AAT2861

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Manufacturer Part Number Value Voltage Temp. Co. Case

AVX 0603ZD105K 1F10X5R 0603

0603ZD225K 2.2F10

TDK

C1608X5R1E105K 1F25

X5R 0603C1608X5R1C225K 2.2F16

C1608X5R1A475K 4.7F10

Murata GRM188R61C105K 1F16X5R 0603

GRM188R61A225K 2.2F10

Taiyo Yuden LMK107BJ475KA 4.7F 10 X5R 0603

Table 13: Surface Mount Capacitors.

ceramic capacitors are used. In general, low ESR may be

defined as less than 100m.

Ceramic composition capacitors are highly recommended

over all other types of capacitors for use with the

AAT2861. Ceramic capacitors offer many advantages

over their tantalum and aluminum electrolytic counter-

parts. A ceramic capacitor typically has very low ESR, is

lowest cost, has a smaller printed circuit board (PCB)

footprint, and is non-polarized. Since ceramic capacitors

are non-polarized, they are not prone to incorrect con-

nection damage.

Equivalent Series Resistance (ESR)

ESR is an important characteristic to consider when

selecting a capacitor. ESR is a resistance internal to a

capacitor, which is caused by the leads, internal connec-

tions, size or area, material composition and ambient

temperature. Capacitor ESR is typically measured in mil-

liohms for ceramic capacitors and can range to more

than several ohms for tantalum or aluminum electrolytic

capacitors.

Ceramic Capacitor Materials

Ceramic capacitors less than 0.1F are typically made

from NPO or COG materials. NPO and C0G materials

typically have tight tolerance and are stable over tem-

perature. Larger capacitor values are typically composed

of X7R, X5R, Z5U or Y5V dielectric materials. Large

ceramic capacitors, typically greater than 2.2F are

often available in low cost Y5V and Z5U dielectrics, but

capacitors greater than 1F are typically not required for

AAT2861 applications.

Capacitor area is another contributor to ESR. Capacitors

that are physically large will have a lower ESR when

compared to an equivalent material smaller capacitor.

These larger size capacitors can improve circuit transient

response when compared to an equal value capacitor in

a smaller package size.

PCB Layout

To achieve adequate electrical and thermal performance,

careful attention must be given to the PCB layout. In the

worst-case operating condition, the chip must dissipate

considerable power at full load. Adequate heat-sinking

must be achieved to ensure intended operation.

Figures 2 and 3 illustrate an example PCB layout. The

bottom of the package features an exposed metal pad-

dle. The exposed paddle acts, thermally, to transfer heat

from the chip and, electrically, as a ground connection.

The junction-to-ambient thermal resistance (JA) for the

connection can be significantly reduced by following a

couple of important PCB design guidelines.

The PCB area directly underneath the package should be

plated so that the exposed paddle can be mated to the

top layer PCB copper during the re-flow process. Multiple

copper plated thru-holes should be used to electrically

and thermally connect the top surface paddle area to

additional ground plane(s) and/or the bottom layer

ground pour.

The chip ground is internally connected to both the

paddle and to the AGND and PGND pins. It is good prac-

tice to connect the GND pins to the exposed paddle area

with traces as shown in the example.

The flying capacitors C1 and C2 should be connected

close to the IC. Trace length should be kept short to

minimize path resistance and potential coupling. The

input and output capacitors should also be placed as

close to the chip as possible.

AAT2861

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Button(s) Pushed Description

SW1

[Push/Release once] LDOA, LDOB and LDOC outputs are programmed to 1.2V. With every subsequent

push/release LDOA, LDOB and LDOC output voltages are incremented according to Table 8.

[Push/hold more than 2 sec] LDOA, LDOB and LDOC outputs will start to cycle through all programmable

voltage settings according to Table 8.

SW2

[Push/Release once] All channels are turned on as Main backlight with 31mA per channel. With every

subsequent push/release the backlight current is decreased according to Table 4.

[Push/hold more than 2 sec] All channels Main and Sub are turned on with 31mA per channel and fade

out sequence is initiated. The cycle proceeds with fade in for Main channels only, followed by fade in se-

quence for Sub channels. When these sequences are ﬁ nished the program will restart fade out sequence

for all Main and Sub channels.

SW3

[Push/Release once] Flash channels are programmed with maximum current and timer. With every sub-

sequent push/release the ﬂ ash current is decreased according to Table 9. The FLASH button needs to be

pressed down simultaneously.

FLASH This button is connected directly to FL_EN pin. Press and hold for the ﬂ ash to be enabled.

Table 14: AAT2861 Evaluation Board User Interface.

Evaluation Board User Interface

The user interface for the AAT2861 evaluation board is

provided by four buttons and a number of connection

terminals. The board is operated by supplying external

power and pressing individual buttons or button combi-

nations. Table 14 indicates the function of each button or

button combination.

To power-on the evaluation board, connect a power sup-

ply or battery to the DC- and DC+ terminals. A red LED

indicates that power is applied.

The evaluation board is made flexible so that the user

can disconnect the enable line from the microcontroller

and apply external enable signal. External enable signal

must be applied to the EN/SET pin.

When applying external enable signal, consideration

must be given to the voltage levels. The externally

applied voltage should not exceed the supply voltage

that is applied to the IN pins of the device (DC+).

The LDO loads can be connected directly to the evalua-

tion board. For adequate performance, be sure to con-

nect the load between LDOA/LDOB/LDOC and DC- as

opposed to some other GND in the system.

AAT2861

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2.2µF

4.7µF

2.2µF

D1D2

OUT

DC+

VDD

GP5

GP4

GP3

4GP2 5

GP1 6

GP0 7

VSS 8

PIC12F675

1µF

330

LED7

RED

14 23

5SW2

14 23

5SW3

14 23

FLASH

DC+

DF2

DF1

14 23

5SW1

OUT

C2+

EN/SET

FL_EN

EN_LDOA

EN_LDOB/C

AGND

7BL2

BL1LDOALDOBINLDOC

12111089

BL3 14

BL4 15

BL5 16

BL6 17

BL7/FL2 18

FL1 19

2122

2324

AAT2861-X

DC+

10K

2.2µF

1.0µF

4.7µF

C1+ IN PGNDC1- C2-

Figure 2: AAT2861 Evaluation Board Schematic.

AAT2861

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Figure 3: AAT2861 Evaluation Board Top Side Layout.

Figure 4: AAT2861 Evaluation Board Bottom Side Layout.

AAT2861

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Component Part# Description Manufacturer

U1 AAT2861IMK-x-T1 High Eff. 1X/1.5X/2X CP for White LED, Triple LDO Skyworks

U2 PIC12F675 8-bit CMOS, FLASH MCU; 8-pin PDIP Microchip

D1-D7 LW M673 Mini TOPLED White LED; SMT OSRAM

DF1, DF2 LXCL PWF1 Mini TOPLED Flash LED; SMT Lumileds, Philips

C1, C2 GRM18x 1.0F, 10V, X5R, 0603, Ceramic Murata

C3, C6, C7, C8 GRM18x 2.2F, 10V, X5R, 0603, Ceramic Murata

C4, C5 GRM18x 4.7F, 10V, X5R, 0603, Ceramic Murata

R1-R3 Chip Resistor 1K, 5%, 1/4W; 0603 Vishay

R4 Chip Resistor 10K, 5%, 1/4W; 0603 Vishay

R6 Chip Resistor 330, 5%, 1/4W; 1206 Vishay

R5 Chip Resistor 0, 5%, 1/4W; 1206 Rohm

LED7 CMD15-21SRC/TR8 Red LED; 1206 Chicago Miniature Lamp

SW1-SW3, FLASH PTS645TL50 Switch Tact, SPST, 5mm ITT Industries

Table 15: AAT2681 Evaluation Board Bill of Materials (BOM),

AAT2861

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Ordering Information

Package Marking1Part Number (Tape and Reel)2

TQFN34-24 4KXYY AAT2861IMK-1-T1

TQFN34-24 4LXYY AAT2861IMK-2-T1

TQFN34-24 4XXYY AAT2861IMK-3-T1

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

4.000

0.050

Top View Bottom View

Side View

Detail “A”

1.700

0.050

Detail “A”

R(5x)

Index Area

0.210

0.040

2.700

0.050

0 + 0.10

- 0.00

0.750

0.050

0.203 REF

0.400 BSC

0.400

0.050

All dimensions in millimeters.

1. XYY = assembly and date code.

2. Sample stock is generally held on part numbers listed in BOLD.

3. The leadless package family, which includes QFN, TQFN, DFN, TDFN, and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing

process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.

AAT2861

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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. Sky-

works may change its documentation, products, services, speciﬁ cations 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 conﬂ icts, incompatibilities, or other difﬁ culties arising from any future changes.

No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided here-

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