ANALOG DEVICES ADD5207 Service Manual

for LCD Backlight Applications

ADD5207

Rev. A

Information furnished by Analog Devices is believed to be accurate and reliable. However, no

Trademarks and registered trademarks are the property of their respective owners.

Fax: [phone] ©2009–2012 Analog Devices, Inc. All rights reserved.

08350-101

L1

10µH

VIN

R

C

6.8kΩ

C

C

2.2nF

R

SET

180kΩ

C2
OPEN

C

IN

10µF

V

IN

ISET COMP GND

SW

D1

OVP

FB1
FB2
FB3
FB4

14 13

4
5
6
7

12113

1

+
–

PWM

9

R

F

100kΩ

FSLCT

2

C

BYPASS

1µF

VDD

8

C

OUT

4µF

ADD5207

C

IN2

0.1µF

SHDN

OFF ON

10

Data Sheet

FEATURES

White LED driver based on inductive boost converter

Integrated 40 V MOSFET with 1.5 A peak current limit
Input voltage range: 6 V to 21 V
Maximum output adjustable up to 36 V
600 kHz to 1 MHz adjustable operating frequency
Typical 39 V fixed overvoltage protection (OVP)
Built-in soft start for boost converter

Drives up to 4 LED current strings

LED current adjustable up to 25 mA for each channel
Headroom control to maximize efficiency
Fixed LED dimming frequency: 8 kHz
LED open fault protection
Brightness control with PWM input

Dimming controls

4-channel operation: 90 degree phase shift between

channels

3-channel operation: 120 degree phase shift between

channels

General

Thermal shutdown
Undervoltage lockout
14-lead, 4 mm × 3 mm LFCSP

APPLICATIONS

Notebook PCs, UMPCs, and monitor displays

Four-String, White LED Driver

GENERAL DESCRIPTION

The ADD5207 is a white LED driver for backlight applications
based on high efficiency, current mode, step-up converter tech­nology. It is designed with a 0.15 Ω, 1.5 A internal switch and a
pin-adjustable operating frequency between 600 kHz and 1 MHz.

The ADD5207 contains four regulated current sources for
uniform LED brightness. Each current source can drive up to
25 mA and the LED-driving current is pin adjustable by an
external resistor. The ADD5207 drives up to four parallel
strings of multiple series-connected LEDs with a ±1.5% current
matching between strings.

The ADD5207 provides phase shift PWM brightness control
methods. LED dimming control is achieved through the PWM
input. The device includes an 8 kHz LED-dimming oscillator
for driving each current source. The ADD5207 operates over an
input voltage range of 6 V to 21 V, but the device can function
with a voltage as low as 5.6 V.

The ADD5207 also has multiple safety protection features to
prevent damage during fault conditions. If any LED is open, the
device automatically disables the faulty current source. The
internal soft start circuit prevents a high inrush current during
startup. Thermal shutdown protection prevents thermal damage.

The ADD5207 is available in a low profile, thermally enhanced,
4 mm × 3 mm × 0.75 mm, 14-lead, RoHS-compliant lead frame
chip scale package (LFCSP) and is specified over the industrial
temperature range of −25°C to +85°C.

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

TYPICAL APPLICATION CIRCUIT

Figure 1.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone]

www.analog.com

ADD5207 Data Sheet

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications ....................................................................................... 1

General Description ......................................................................... 1

Typical Application Circuit ............................................................. 1

Revision History ............................................................................... 2

Functional Block Diagram .............................................................. 3

Specifications ..................................................................................... 4

Step-Up Switching Regulator Specifications ............................. 4

LED Current Regulation Specifications .................................... 5

General Specifications ................................................................. 6

Absolute Maximum Ratings ............................................................ 7

Thermal Resistance ...................................................................... 7

ESD Caution .................................................................................. 7

Pin Configuration and Function Descriptions ............................. 8

Typical Performance Characteristics ..............................................9

Theory of Operation ...................................................................... 11

Current Mode, Step-Up Switching Regulator Operation ..... 11

Internal 3.3 V Regulator ............................................................ 11

Boost Converter Switching Frequency .................................... 11

Dimming Frequency (f

Current Source ............................................................................ 11

PWM Dimming Mode .............................................................. 11

Safety Features ............................................................................ 11

External Component Selection Guide ..................................... 12

Layout Guidelines....................................................................... 13

Typical Application Circuits ......................................................... 15

Outline Dimensions ....................................................................... 16

Ordering Guide .......................................................................... 16

) ...................................................... 11

PWM

REVISION HISTORY

2/12—Rev. Sp0 to Rev. A

Replaced Block Diagram with Typical Application Circuit ........ 1

Changes to Features Section and General Description Section . 1
Changes to Current Mode, Step-Up Switching Regulator
Operation Section, Boost Converter Switching Frequency
Section, PWM Dimming Mode Section, Phase Shift PWM

Dimming Section, and Safety Features Section .......................... 11

Changes to Overvoltage Protection (OVP) Section .................. 11

Changes to Open-Loop Protection (OLP) Section,
Undervoltage Lockout (UVLO) Section, and Thermal

Protection Section .......................................................................... 12

Changes to Layout Guidelines Section ........................................ 13

7/09—Revision Sp0: Initial Version

Rev. A | Page 2 of 16

Data Sheet ADD5207

ADD5207

VIN VDD SHDN OVP

VOUT_FB

SW

LINEAR

REGULATOR

VOLTAGE

REFERENCE

SHUTDOWN

ERROR

AMP

UVP

COMP

PWM

COMP

UVP
REF

g

m

LL

REF

VOUT_FB

LL COMP

DCOMP

HEADROOM CO NTROL

CURRENT SOURCE 1

CURRENT SOURCE 2

CURRENT SOURCE 3

CURRENT SOURCE 4

PWM

500kΩ

ISET

REF

VDD

GND

500kΩ

GND

COMP

PWM

DUTY

EXTRACTOR

SOFT START

CURRENT SENSE

OSC

LED OPEN/SHORT
FAULT DETECTOR

DREF

OVP
REF

GND

THERMAL

SHUTDOWN

R

S

Q

FSLCT

GND

FB1

FB2

CURRENT SOURCE DRIVER

FPWM OSCILLATOR

1 108 13 14

2

12

4

5

FB3

6

FB4

7

9

3

11

08350-002

+

+

FUNCTIONAL BLOCK DIAGRAM

Figure 2. Functional Block Diagram

Rev. A | Page 3 of 16

ADD5207 Data Sheet

Parameter

Symbol

Test Conditions/Comments

Min

Typ

Max

Unit

SPECIFICATIONS

STEP-UP SWITCHING REGULATOR SPECIFICATIONS

VIN = 12 V,

Table 1.

SUPPLY

Input Voltage Range VIN 6 21 V

BOOST OUTPUT

Output Voltage V

SWITCH

On Resistance R
Leakage Current I
Peak Current Limit ICL Duty cycle (D) = D

OSCILLATOR

Switching Frequency fSW RF = 97 kΩ 800 1000 1200 kHz
Maximum Duty Cycle D

SOFT START

Soft Start Time tSS 1.1 ms

OVERVOLTAGE PROTECTION

Overvoltage Rising Threshold on OVP Pin V
Overvoltage Hysteresis on OVP Pin V

SHDN

= high, TA = −25°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.

36 V

OUT

DS(ON)

1 µA

LKG

RF = 97 kΩ 84 90 %

MAX

36.5 39 40 V

OVPR

OVP_HYS

VIN = 12 V, ISW = 100 mA 150 300 mΩ

MAX

0.1 0.7 1.4 V

1.5 A

Rev. A | Page 4 of 16

Data Sheet ADD5207

Current Matching Between Strings2

R

= 180 kΩ

−1.5 +1.5

%

LED CURRENT REGULATION SPECIFICATIONS

VIN = 12 V,

Table 2.

Parameter Symbol Test Conditions/Comments Min Typ Max Unit

CURRENT SOURCE

ISET Pin Voltage V
Adjustable LED Current1 I
Constant Current Sink of 20 mA2 I
Minimum Headroom Voltage2 V

LED Current Accuracy2 R
Current Source Leakage Current 1 µA

FPWM GENERATOR

Dimming Frequency f

LED FAULT DETECTION

Open Fault Delay1 t

1

This electrical specification is guaranteed by design.

2

Tested at TA = +25°C.

SHDN

= high, TA = −25°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.

6 V ≤ VIN ≤ 21 V 1.14 1.18 1.22 V

SET

0 25 mA

LED

R

LED20

R

HR20

PWM

D_OPENFAULT

6.5 µs

= 180 kΩ 19.4 20 20.6 mA

SET

= 180 kΩ 0.66 0.9 V

SET

SET

= 180 kΩ −3 +3 %

SET

6.8 8.0 9.2 kHz

Rev. A | Page 5 of 16