19-3211; Rev 0; 1/08
8-String White LED Driver with
SMBus for LCD Panel Applications
General Description
The MAX17061 is a high-efficiency driver for white light-
emitting diodes (LEDs). It is designed for large liquid-
crystal displays (LCDs) that employ an array of LEDs as
the light source. An internal switch current-mode step-up
controller drives the LED array, which can be configured
for up to eight strings in parallel and 10 LEDs per string.
Each string is terminated with ballast that achieves ±1.5%
current-regulation accuracy between strings, ensuring
even LED brightness. The MAX17061 has a wide input-
voltage range from 4.5V to 26V, and provides a fixed
25mA or adjustable 15mA to 30mA full-scale LED current.
The MAX17061 internally generates a DPWM signal for
accurate WLED dimming control. The DPWM frequency
is resistor programmable, while DPWM duty cycle is con-
trolled directly from an external PWM signal or through a
control word through the MAX17061’s SMBus™ inter-
face. This DPWM control provides a dimming range with
8-bit resolution and supports Intel display-power-saving
technology (DPST) to maximize battery life.
The MAX17061 has multiple features to protect the con-
troller from fault conditions. Separate feedback loops
limit the output voltage under any circumstance, ensur-
ing safe operation. Once an open string is detected,
the string is disabled while other strings operate nor-
mally. The MAX17061 also features short LED detec-
tion. The shorted strings are also disabled after a 2ms
fault blanking interval. The controller features cycle-by-
cycle current limit to provide stable operation and soft-
start capability. If the MAX17061 is in current-limit
condition, the step-up converter is latched off after an
internal timer expires. A thermal-shutdown circuit pro-
vides another level of protection.
The MAX17061’s step-up controller features an internal
150mΩ (typ), 45V (max) power MOSFET with local cur-
rent-sense amplifier for accurate cycle-by-cycle current
limit. This architecture greatly simplifies the external cir-
cuitry and saves PCB space. Low-feedback voltage at
each LED string 625mV (typ) at 25mA LED current helps
reduce power loss and improve efficiency. The
MAX17061 features selectable switching frequency
(500kHz, 750kHz, or 1MHz), which enables a wide vari-
ety of applications that can trade off component size for
operating frequency.
The MAX17061 is available in a thermally enhanced
28-pin, 4mm x 4mm Thin QFN package.
Features
o
Accurate Dimming Control Using SMBus, PWM
Interface
o
Dimming Range with 8-Bit Resolution
o
Adjustable DPWM Frequency with 1.5% Accuracy
o
Up to Eight Parallel Strings Multiple Series-
Connected LEDs
o
±1.5% Current Regulation Accuracy Between
Strings
o
Low String Feedback Voltage: 625mV at 25mA
LED Current
o
Full-Scale LED Current Adjustable from 15mA to
30mA, or Preset 25mA
o
Open and Short LED Protections
o
Output Overvoltage Protection
o
0.15Ω Internal HV Power MOSFET (45V max)
o
Wide Input-Voltage Range from 4.5V to 26V
o
500kHz/750kHz/1MHz Selectable Switching
Frequency
o
Small 28-Pin, 4mm x 4mm, Thin QFN package
MAX17061
Ordering Information
PART
MAX17061ETI+
TEMP RANGE PIN-PACKAGE
-40
o
C to +85
o
C 28 Thin QFN (4mm x 4mm)
+Denotes
a lead-free package.
Simplified Operating Circuit
L1
V
IN
D1
V
OUT
V
DD
IN
V
CC
ISET
LX1, 2
PGND1, 2
R1
CCV
OV
R2
MAX17061
PWM
PWMI
PWMO
FB1
GND
N.C.
CLK
DATA
OSC
SCL
SDA
FSET
EP
FB2
FB3
FB4
FB5
FB6
FB7
FB8
Applications
Notebook, Subnotebook,
and Tablet Computer
Displays
Automotive Systems
Handy Terminals
Pin Configuration appears at end of data sheet.
SMBus is a trademark of Intel Corp.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
8-String White LED Driver with
SMBus for LCD Panel Applications
MAX17061
ABSOLUTE MAXIMUM RATINGS
IN to GND ..............................................................-0.3V to +28V
FB_, LX_ to GND ....................................................-0.3V to +45V
PGND_ to GND......................................................-0.3V to +0.3V
V
CC
, V
DD
, PWMI, SDA, SCL to GND ........................-0.3V to +6V
ISET, CCV, PWMO, FSET, OSC,
OV to GND ................................................-0.3V to V
CC
+ 0.3V
Continuous Power Dissipation (T
A
= +70°C)
28-Pin Thin QFN (derate 16.9mW/°C above +70°C)...1667mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, C
CCV
= 0.022µF, R
CCV
= 5.1kΩ, V
ISET
= V
OSC
= V
DD
= V
CC
, R
FSET
= 464kΩ, V
PWMI
= GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
IN Input Voltage Range
IN Quiescent Current
IN Quiescent Current
V
CC
Output Voltage
V
CC
Current Limit
V
CC
UVLO Threshold
BOOST CONVERTER
LX On-Resistance
LX Leakage Current
Operating Frequency
20mA from LX_ to PGND
45V on LX_
V
OSC
= V
CC
V
OSC
= open
V
OSC
= GND
OSC High-Level Threshold
OSC Midlevel Threshold
OSC Low-Level Threshold
Minimum Duty Cycle
Maximum Duty Cycle
LX Current Limit
CONTROL INPUT
SDA, SCL Logic Input-High Level
SDA, SCL Logic Input-Low Level
PWMI Logic Input-High Level
PWMI Logic Input-Low Level
2.1
0.8
2.1
0.8
V
V
V
V
Duty cycle = 75% (Note 1)
PWM mode (Note 1)
Pulse skipping, no load (Note 1)
94.0
1.6
10
0
95.5
97.0
0.9
675
450
V
CC
-
0.4
1.5
V
CC
-
2.0
0.4
1.0
750
500
0.15
0.3
1
1.1
825
550
Ω
µA
MHz
kHz
V
V
V
%
%
A
V
IN
= V
CC
V
CC
= open
MAX17061 is enabled at
minimum brightness, no load
V
IN
= 26V
V
IN
= V
CC
= 5V
4.7
3.90
15
4.00
CONDITIONS
MIN
4.5
5.5
1.24
TYP
MAX
5.5
26.0
2
10
5.0
4.35
40
4.25
5.3
4.80
70
4.45
UNITS
V
mA
µA
V
mA
V
MAX17061 is disabled, V
IN
= 12V
MAX17061 is enabled, 6V < V
IN
< 26V, 0 < I
VCC
< 10mA
MAX17061 is disabled, V
IN
= 12V
V
CC
is forced to 4.5V
Rising edge, typical hysteresis = 85mV
2
_______________________________________________________________________________________
8-String White LED Driver with
SMBus for LCD Panel Applications
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, C
CCV
= 0.022µF, R
CCV
= 5.1kΩ, V
ISET
= V
OSC
= V
DD
= V
CC
, R
FSET
= 464kΩ, V
PWMI
= GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
INPUT LEAKAGE
PWMI Leakage Current
ISET, FSET Leakage Current
OV Leakage Current
SDA, SCL Input Bias Current
SDA Output Low-Sink Current
OSC Leakage Current
LED CURRENT
ISET = V
CC
Full-Scale FB_ Output Current
R
ISET
= 133kΩ
R
ISET
= 200kΩ
R
ISET
= 266kΩ
ISET High-Level Threshold
ISET Output Voltage
Current Regulation Between Strings
24.5
28.8
19.3
14.4
V
CC
-
0.4
Full brightness
I
FB_
= 25mA
Minimum FB_ Regulation Voltage
I
FB_
= 30mA
I
FB_
= 20mA
I
FB_
= 15mA
Maximum FB_ Ripple
FB_ On-Resistance
FB_ Leakage Current
FAULT PROTECTION
OV Threshold Voltage
FB_ Overvoltage Threshold
FB_ Undervoltage Threshold
OV Undervoltage Threshold
(Boost Global Fail)
Thermal-Shutdown Threshold
Overcurrent FAULT Shutdown Timer
FB_ Overvoltage Fault Timer
(Note 1)
I
PEAK
> 3.3A at duty = 0%
Full brightness
88
1.7
Rising edge, typical hysteresis = 60mV
V
IN
> 5.5V
1.166
5.2
130
48
1.236
5.6
175
84
160
128
2
168
2.3
1.306
6.0
220
120
V
V
mV
mV
°C
µs
ms
I
FB_
= 20mA (C
OUT
= 1µF, V
OSC
= V
CC
) (Note1)
V
FB_
= 50mV (includes 10Ω sense resistor)
V
FB_
= 26V, T
A
= +25°C
V
FB_
= 45V, T
A
= +25°C
2.5
1.166
-1.5
475
575
380
285
1.236
625
750
500
375
120
17.5
1.306
+1.5
910
1100
740
560
200
28.4
1
4
mV
P/P
Ω
µA
mV
25.0
30.0
20.0
15.0
25.5
31.2
20.7
15.6
V
V
%
mA
V
SDA
= 0.4V
ISET , FSET to V
CC
-0.1
-1
4
-3
+3
-0.3
+0.3
+1
+0.1
+1
µA
µA
µA
µA
mA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
MAX17061
_______________________________________________________________________________________
3
8-String White LED Driver with
SMBus for LCD Panel Applications
MAX17061
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, C
CCV
= 0.022µF, R
CCV
= 5.1kΩ, V
ISET
= V
OSC
= V
DD
= V
CC
, R
FSET
= 464kΩ, V
PWMI
= GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
PWM FILTER
PWM Output Impedance
R
FSET
= 464kΩ
DPWM Oscillator Frequency
R
FSET
= 113kΩ
R
FSET
= 65kΩ
R
FSET
= 42kΩ
PWMI Input-Frequency Range
PWMI Full-Range Accuracy
PWMI duty cycle = 100%
PWMI Brightness Setting
SMBus TIMING SPECIFICATION
SMBus Frequency
Bus Free Time
START Condition Hold
Time from SCL
START Condition Setup
Time from SCL
STOP Condition Setup
Time from SCL
SDA Hold Time from SCL
SDA Setup Time from SCL
SCL Low Period
SCL High Period
FSMB
TBUF
THD:STA
TSU:STA
TSU:STO
THD:DAT
TSU:DAT
T
LOW
T
HIGH
10
4.7
4
4.7
4
300
250
4.7
4
100
kHz
µs
µs
µs
µs
ns
ns
µs
µs
PWMI duty cycle = 50%
PWMI duty cycle = 0%
98
48
2.6
100
50
2.7
52
2.8
%
5
20
197
750
1.270
40
200
785
1.335
2
10
100
5
60
203
820
1.400
kΩ
Hz
kHz
kHz
LSB
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, C
CCV
= 0.022µF, R
CCV
= 5.1kΩ, V
ISET
= V
OSC
= V
DD
= V
CC
, R
FSET
= 464kΩ, V
PWMI
= GND,
T
A
= -40°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
IN Input Voltage Range
V
IN
= V
CC
VCC = open
MAX17061 is enabled at
minimum brightness, no load
V
IN
= 26V
V
IN
= V
CC
= 5V
4.7
3.9
12
4.00
CONDITIONS
MIN
4.5
5.5
TYP
MAX
5.5
26.0
2
2
10
5.3
4.8
70
4.45
UNITS
V
mA
µA
V
mA
V
IN Quiescent Current
MAX17061 is disabled, V
IN
= 12V
V
CC
Output Voltage
V
CC
Current Limit
V
CC
UVLO Threshold
MAX17061 is enabled, 6V < V
IN
< 26V, 0 < I
VCC
< 10mA
MAX17061 is disabled, V
IN
= 12V
V
CC
is forced to 4.5V
Rising edge, typical hysteresis = 85mV
4
_______________________________________________________________________________________
8-String White LED Driver with
SMBus for LCD Panel Applications
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, C
CCV
= 0.022µF, R
CCV
= 5.1kΩ, V
ISET
= V
OSC
= V
DD
= V
CC
, R
FSET
= 464kΩ, V
PWMI
= GND,
T
A
= -40°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
BOOST CONVERTER
LX On-Resistance
LX Leakage Current
Operating Frequency
20mA from LX_ to PGND
45V on LX_
V
OSC
= V
CC
V
OSC
= open
V
OSC
= GND
OSC High-Level Threshold
OSC Midlevel Threshold
OSC Low-Level Threshold
Maximum Duty Cycle
LX Current Limit
CONTROL INPUT
SDA, SCL Logic Input-High Level
SDA, SCL Logic Input-Low Level
PWMI Logic Input-High Level
PWMI Logic Input-Low Level
INPUT LEAKAGE
PWMI Leakage Current
ISET, FSET Leakage Current
OV Leakage Current
SDA, SCL Input Bias Current
SDA Output-Low Sink Current
OSC Leakage Current
LED CURRENT
ISET = V
CC
Full-Scale FB_ Output Current
R
ISET =
133kΩ
R
ISET
= 200kΩ
R
ISET =
266kΩ
ISET High-Level Threshold
ISET Output Voltage
Current Regulation Between Strings
Full brightness
I
FB_
= 25mA
Minimum FB_ Regulation Voltage
I
FB_
= 30mA
I
FB_
= 20mA
I
FB_
= 15mA
Maximum FB_ Ripple
FB_ On-Resistance
I
FB_
= 20mA (C
OUT
= 1µF, V
OSC
= V
CC
)
V
FB_
= 50mV (includes 10Ω sense resistor)
24.5
28.6
19.0
14.3
V
CC
-
0.4
1.166
-1.5
425
575
380
285
25.5
31.4
21.0
15.7
V
1.306
+1.5
910
1100
740
560
200
28.4
mV
P/P
Ω
mV
V
%
mA
V
SDA
= 0.4V
ISET , FSET to V
CC
-0.1
-1
4
-3
+3
-0.3
+0.3
+1
+0.1
+1
µA
µA
µA
µA
mA
µA
2.1
0.8
2.1
0.8
V
V
V
V
Duty cycle = 75%
94
1.6
0.89
675
450
V
CC
-
0.4
1.5
0.3
1
1.10
825
560
Ω
µA
MHz
kHz
kHz
V
V
CC
-
2.0
0.4
97
V
V
%
A
CONDITIONS
MIN
TYP
MAX
UNITS
MAX17061
_______________________________________________________________________________________
5
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