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
Four-String, White LED Driver
for LCD Backlight Applications
ADD5207
GENERAL DESCRIPTION
The
ADD5207
is a white LED driver for backlight applications
based on high efficiency, current mode, step-up converter tech-
nology. 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.
APPLICATIONS
Notebook PCs, UMPCs, and monitor displays
TYPICAL APPLICATION CIRCUIT
V
IN
+
–
C
IN
10µF
C
IN2
0.1µF
L1
10µH
1
VIN
D1
14
13
C
OUT
4µF
SW
OVP
ADD5207
9
PWM
10
SHDN
8
VDD
OFF ON
C
BYPASS
1µF
R
F
100kΩ
FB1
4
FB2
5
2
FSLCT
FB3
6
COMP
11
ISET
3
FB4
7
GND
12
R
SET
180kΩ
R
C
6.8kΩ
Figure 1.
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
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.
Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2009–2012 Analog Devices, Inc. All rights reserved.
08350-101
C
C
2.2nF
C2
OPEN
ADD5207
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
Data Sheet
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
PWM
) ...................................................... 11
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
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
FUNCTIONAL BLOCK DIAGRAM
VIN
1
ADD5207
VDD
8
SHDN
10
OVP
13
SW
14
LINEAR
REGULATOR
SHUTDOWN
VOLTAGE
REFERENCE
UVP
COMP
UVP
REF
ERROR
AMP
LL
REF
PWM
COMP
THERMAL
SHUTDOWN
500kΩ
GND
VOUT_FB
ADD5207
GND
OVP
REF
LL COMP
R
Q
S
VOUT_FB
g
m
COMP
11
OSC
DREF
DCOMP
+
+
CURRENT SENSE
2
FSLCT
SOFT START
HEADROOM CONTROL
VDD
LED OPEN/SHORT
FAULT DETECTOR
12
GND
CURRENT SOURCE 1
REF
CURRENT SOURCE 2
4
FB1
5
FB2
ISET
3
CURRENT SOURCE 3
6
FB3
CURRENT SOURCE 4
PWM
DUTY
EXTRACTOR
500kΩ
GND
7
FB4
PWM
9
CURRENT SOURCE DRIVER
FPWM OSCILLATOR
Figure 2. Functional Block Diagram
Rev. A | Page 3 of 16
08350-002
ADD5207
SPECIFICATIONS
STEP-UP SWITCHING REGULATOR SPECIFICATIONS
V
IN
= 12 V, SHDN = high, T
A
= −25°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.
Table 1.
Parameter
SUPPLY
Input Voltage Range
BOOST OUTPUT
Output Voltage
SWITCH
On Resistance
Leakage Current
Peak Current Limit
OSCILLATOR
Switching Frequency
Maximum Duty Cycle
SOFT START
Soft Start Time
OVERVOLTAGE PROTECTION
Overvoltage Rising Threshold on OVP Pin
Overvoltage Hysteresis on OVP Pin
Symbol
V
IN
V
OUT
R
DS(ON)
I
LKG
I
CL
f
SW
D
MAX
t
SS
V
OVPR
V
OVP_HYS
36.5
0.1
V
IN
= 12 V, I
SW
= 100 mA
Duty cycle (D) = D
MAX
R
F
= 97 kΩ
R
F
= 97 kΩ
1.5
800
84
1000
90
1.1
39
0.7
150
Test Conditions/Comments
Min
6
Typ
Data Sheet
Max
21
36
300
1
Unit
V
V
mΩ
µA
A
kHz
%
ms
1200
40
1.4
V
V
Rev. A | Page 4 of 16
Data Sheet
LED CURRENT REGULATION SPECIFICATIONS
V
IN
= 12 V, SHDN = high, T
A
= −25°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.
Table 2.
Parameter
CURRENT SOURCE
ISET Pin Voltage
Adjustable LED Current
1
Constant Current Sink of 20 mA
2
Minimum Headroom Voltage
2
Current Matching Between Strings
2
LED Current Accuracy
2
Current Source Leakage Current
FPWM GENERATOR
Dimming Frequency
LED FAULT DETECTION
Open Fault Delay
1
1
2
ADD5207
Symbol
V
SET
I
LED
I
LED20
V
HR20
Test Conditions/Comments
6 V ≤ V
IN
≤ 21 V
R
SET
= 180 kΩ
R
SET
= 180 kΩ
R
SET
= 180 kΩ
R
SET
= 180 kΩ
Min
1.14
0
19.4
−1.5
−3
Typ
1.18
20
0.66
Max
1.22
25
20.6
0.9
+1.5
+3
1
9.2
6.5
Unit
V
mA
mA
V
%
%
µA
kHz
µs
f
PWM
t
D_OPENFAULT
6.8
8.0
This electrical specification is guaranteed by design.
Tested at T
A
= +25°C.
Rev. A | Page 5 of 16
