EVALUATION KIT AVAILABLE
MAX17105
General Description
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Features
●
6V to 28V Input Supply Voltage
●
Up to Eight Parallel-String Multiple Series Connected
LEDs
●
500kHz-to-2MHz Adjustable Switching Frequency
● 0.15Ω Internal HV Power MOSFET (45V max)
●
Low-String Feedback Voltage: 500mV at 20mA LED
current
●
Full-Scale LED Current Adjustable from 0mA to 30mA
●
±2% Current Regulation Accuracy Between Strings
●
100:1 Dimming Ratio at 25kHz Direct PWM
Frequency
●
100Hz to 30kHz PWMI Input Range for DPWM Mode
and 10kHz ±5% for SMBus Mode
●
100Hz to 5kHz Adjustable DPWM Frequency
●
Full-Range Dimming with 8-Bit Resolution
●
Open and Short LED Protection
●
Output Overvoltage Protection
●
Thermal Shutdown
●
FAULT Output to Drive p-Channel MOSFET
●
Small 24-Pin, 4mm x 4mm, Thin QFN Package
The MAX17105 is a high-efficiency driver for white-light-
emitting diodes (WLEDs). 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 8 strings in parallel and 10 LEDs per string. Each
string is terminated with ballast that achieves ±2% current
regulation accuracy, ensuring even LED brightness. The
MAX17105 has a wide input voltage range from 6V to
28V, and provides adjustable 0 to 30mA full-scale LED
current.
The MAX17105 can internally generate a digitally adjust-
ed pulse-width modulation (DPWM) signal for accurate
WLED dimming control. The DPWM frequency is resis-
tor programmable, while DPWM duty cycle is controlled
directly from an external PWM signal or through a control
word through the MAX17105’s SMBus interface. This
DPWM control provides a dimming range with 8-bit reso-
lution and supports Intel display power-saving technology
(DPST) to maximize battery life. The MAX17105 also has
direct PWM control mode, in which the PWMI directly con-
trols the LED current turn on/off and the SMBus interface
is disabled.
The MAX17105 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 normally.
The MAX17105 also features short LED detection. The
shorted strings are also disabled. The controller features
cycle-by-cycle current limit to provide constant operation
and soft-start capability. If the MAX17105 is in current-
limit condition, the step-up regulator is latched off after an
internal timer expires. A thermal-shutdown circuit provides
another level of protection. When the input overcurrent-
limit fault, thermal shutdown, or output-voltage short con-
dition happens, the input p-channel MOSFET is turned
off and the step-up regulator output is isolated from the
input supply.
The MAX17105 is available in a thermally enhanced,
24-pin, 4mm x 4mm, thin QFN package with exposed pad.
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX17105ETG+
-40°C to +85°C
24 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Pin Configuration
PGND
FB8
FB6
FB5
14
18
LX 19
PWMI 20
EN 21
SCL 22
SDA 23
DFSET 24
1
COMP
2
ISET
3
PWMO
4
OSC
5
OVP
6
V
CC
17
FB7
16
15
FB4
13
12
11
FB3
FB2
FB1
SGND
FAULT
IN
10
9
8
7
TOP VIEW
MAX17105
Applications
●
Notebook, Subnotebook,
and Tablet Computer
Displays
●
Handy Terminals
THIN QFN
4mm x 4mm
Simplified Operating Circuit
appears at end of data sheet.
19-4562; Rev 2; 9/14
MAX17105
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Absolute Maximum Ratings
FAULT, IN to SGND ..............................................-0.3V to +30V
FB_, LX to PGND ..................................................-0.3V to +45V
PGND to SGND....................................................-0.3V to +0.3V
V
CC
, EN, PWMI, SDA, SCL to SGND ....................-0.3V to +6V
COMP, ISET, OSC, OVP,
PWMO, DFSET to SGND......................... -0.3V to (V
CC
+ 0.3V)
LX Switch Maximum Continuous RMS Current ...................1.6A
Continuous Power Dissipation (T
A
= +70°C)
Thin QFN (derate 20.8mW/°C above +70°C)............1667mW
(single-layer board)
Thin QFN (derate 27.8mW/°C above +70°C)............2222mW
(multilayer board)
Operating Temperature Range ........................... -40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°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
COMP
= 33nF, R
COMP
= 1kΩ, R
ISET
= 50kΩ, R
OSC
= 100kΩ, R
DFSET
= 250kΩ, PWMI = SGND,
C
PWMO
= 1µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SUPPLY
V
CC
= open, EN = high
IN Input Voltage Range (Note 1)
IN Input Voltage UVLO Threshold
(SMBus Mode Only) (Note 4)
EN = SGND, SMBus mode
(Note 5)
All functions available
SMBus interface only
5.5
6.3
3.9
5.9
5.75
4.0
6.05
5.9
2.0
0.7
30
4.7
3.7
15
4.00
5.0
4.6
40
4.3
0.15
1.7
0.9
0.4
93
2.0
1.0
0.5
50
95
50
97
6.2
6.05
3.0
1.1
60
5.3
4.95
70
4.45
0.3
1
2.3
1.1
0.6
ns
%
ns
MHz
mA
V
W
µA
V
mA
mA
µA
V
28
28
V
CONDITIONS
MIN
TYP
MAX
UNITS
Rising edge, hysteresis = 150mV
Falling edge, hysteresis = 150mV
MAX17105 is enabled at minimum brightness, in
SMBus mode and no-load, V
IN
= 28V
IN Quiescent Current
MAX17105 is enabled in SMBus mode and is under IN
UVLO, V
IN
= 5.5V
MAX17105 is disabled
MAX17105 is enabled, 6V < V
IN
< 28V, 0 < I
VCC
<
10mA
MAX17105 is disabled, V
IN
= 12V
V
CC
is forced to 4.5V
Rising edge, typical hysteresis = 85mV
100mA from LX to PGND
40V on LX, T
A
= +25°C
R
OSC
= 50kW
R
OSC
= 100kW
R
OSC
= 200kW
(Note 1)
At f
SW
= 1MHz
V
CC
Output Voltage
V
CC
Current Limit
V
CC
UVLO Threshold
STEP-UP REGULATOR
LX On-Resistance
LX Leakage Current
Operating Frequency
Minimum On-Time
Maximum Duty Cycle
Minimum Off-Time
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Maxim Integrated
│
2
MAX17105
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics (continued)
(Circuit of Figure 1. V
IN
= 12V, C
COMP
= 33nF, R
COMP
= 1kΩ, R
ISET
= 50kΩ, R
OSC
= 100kΩ, R
DFSET
= 250kΩ, PWMI = SGND,
C
PWMO
= 1µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
LX Current Limit
CONTROL INPUT
Logic-Input High Level
Logic-Input Low Level
INPUT LEAKAGE
PWMI Leakage Current
Logic Input Bias Current
OVP Leakage Current
SDA Output-Low Sink Current
LED CURRENT
Full-Scale FB_ Output Current-
Adjustable Range (Note 4)
PWM-only dimming mode
SMBus-enabled dimming modes
R
ISET
= 33.3kW
Full-Scale FB_ Output Current
R
ISET
= 50.0kW
R
ISET
= 66.6kW
V
ISET
<
0.4V
ISET Output Voltage
Current Regulation Between
Strings
Minimum FB_ Regulation
Voltage
FB_ On-Resistance
FB_ Leakage Current
FB_ On-Time
FAULT PROTECTION
OVP Threshold Voltage
OVP Shutdown Voltage
OVP Global Fail
FB_ UVLO Threshold
FB_ Overvoltage Threshold
FB_ Check LED Source Current
FB_ Check LED Time
FB open
Rising edge, hysteresis = 60mV
Rising edge
48
140
7.4
0.4
1
220
8
1.15
1.25
1.35
120
300
8.6
1.35
V
V
mV
mV
V
mA
ms
I
FB_
= 30mA
I
FB_
= 20mA
I
FB_
= 15mA
I
FB_
= 30mA
I
FB_
= 20mA
I
FB_
= 15mA
V
FB_
= 50mV
V
FB_
= 40V, T
A
= +25°C
400
480
450
15
0.1
26
5
W
µA
ns
15
15
29.1
19.4
14.45
0.2
1.1
-2.0
-2.0
-2.0
30.0
20.0
15.0
0.3
1.2
30
25
30.9
20.6
15.55
0.4
1.3
+2.0
+2.0
+2.0
770
mV
%
V
mA
mA
T
A
= +25°C
T
A
= +25°C, EN, SDA, SCL
TA
= +25°C
CONDITIONS
Duty cycle = 75% (Note 1)
SDA, SCL, PWMI, EN
SDA, SCL, PWMI, EN
MIN
2.4
2.1
TYP
2.9
MAX
3.4
UNITS
A
V
0.8
-0.1
-1
-0.1
4
+0.1
+1
+0.1
V
µA
µA
µA
mA
V
SDA
= 0.4V
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Maxim Integrated
│
3
MAX17105
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics (continued)
PARAMETER
FB_ Overvoltage Fault Timer
Thermal-Shutdown Threshold
Overcurrent FAULT Shutdown Timer
FAULT High-Level Leakage Current
FAULT Low-Level Clamp Voltage
FAULT Charge Current
PWM FILTER
PWM Output Impedance
(Note 1)
(Circuit of Figure 1. V
IN
= 12V, C
COMP
= 33nF, R
COMP
= 1kΩ, R
ISET
= 50kΩ, R
OSC
= 100kΩ, R
DFSET
= 250kΩ, PWMI = SGND,
C
PWMO
= 1µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
CONDITIONS
MIN
88
I
PEAK
> 2.9A at duty = 75%
V
FAULT
= V
IN
= 28V, T
A
= +25°C
V
IN
–
5.5
45
20
R
DFSET
= 500kW
DPWM Oscillator Frequency
R
DFSET
= 250kW
R
DFSET
= 25kW
R
DFSET
= 10kW
DFSET Short-Detection
Threshold Voltage
R
DFSET
= 500kW
DFSET Source Current
R
DFSET
= 250kW
R
DFSET
= 25kW
R
DFSET
= 10kW
PWMI Input Frequency Range
DPST/SMBus mode
Direct-PWM mode
SMBus mode, PWMI duty cycle = 98%
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
f
SMB
t
BUF
t
HD:STA
t
SU:STA
t
SU:STO
t
HD:DAT
t
SU: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
SMBus mode, PWMI duty cycle = 50%
SMBus mode, PWMI duty cycle = 0%
9.5
0.1
97.5
48
0.2
98
50
0.4
4.4
190
40
100
200
2
5.0
210
4.15
7.85
40
55
10.0
10.5
30.0
98.5
52
0.6
%
kHz
µA
5.5
300
210
V
IN
-
5
72
TYP
128
+150
128
168
1
V
IN
–
4.5
65
60
MAX
168
UNITS
µs
°C
µs
µA
V
µA
kW
Hz
kHz
mV
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Maxim Integrated
│
4
MAX17105
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics
PARAMETER
SUPPLY
IN Input Voltage Range (Note 1)
IN Input Voltage UVLO
Threshold (SMBus Mode Only)
(Note 2)
(Circuit of Figure 1. V
IN
= 12V, C
COMP
= 33nF, R
COMP
= 1kΩ, R
ISET
= 50kΩ, R
OSC
= 100kΩ, R
DFSET
= 250kΩ, PWMI = SGND,
C
PWMO
= 1µF,
T
A
= -40°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
CONDITIONS
V
CC
= open, EN = high (Note 5)
EN = SGND, SMBus mode
MIN
5.5
6.3
3.9
5.9
5.75
4.0
6.2
6.05
3.0
mA
1.1
60
4.7
3.7
15
4.00
5.3
4.95
70
4.45
0.3
1.7
0.9
0.45
93
2.4
2.1
0.8
4
-1
15
15
28.8
18.9
14.25
0.2
-2.5
-2.5
-2.5
+1
30
25
31.2
21
15.75
0.4
+2.5
+2.5
+2.5
770
26
400
mV
W
ns
%
mA
2.3
1.1
0.6
98
3.4
%
A
V
V
mA
µA
mA
MHz
µA
V
mA
V
W
V
TYP
MAX
28
28
V
UNITS
All functions available
SMBus interface only
Rising edge, hysteresis = 150mV
Falling edge, hysteresis = 150mV
MAX17105 is enabled at minimum brightness,
in SMBus mode and no load, V
IN
= 28V
IN Quiescent Current
MAX17105 is enabled in SMBus mode, and is under
IN UVLO, V
IN
= 5.5V
MAX17105 is disabled
MAX17105 is enabled, 6V < V
IN
< 28V, 0 < I
VCC
< 10mA
MAX17105 is disabled, V
IN
= 12V
V
CC
is forced to 4.5V
V
CC
Output Voltage
V
CC
Current Limit
V
CC
UVLO Threshold
LX On-Resistance
Operating Frequency
Maximum Duty Cycle
LX Current Limit
CONTROL INPUT
Logic-Input High Level
Logic-Input Low Level
SDA Output-Low Sink Current
SDA, SCL Input Bias Current
LED CURRENT
Full-Scale FB_ Output Current
Adjustable Range (Note 3)
Rising edge, typical hysteresis = 85mV
100mA from LX to PGND
R
OSC
= 50kW
R
OSC
= 100kW
R
OSC
= 200kW
At f
SW
= 1MHz
Duty cycle = 75%
SDA, SCL, PWMI, EN
SDA, SCL, PWMI, EN
V
SDA
= 0.4V
T
A
= +25NC
STEP-UP REGULATOR
PWM only dimming mode
SMBus-enabled dimming modes
R
ISET
= 33.3kW
R
ISET
= 50.0kW
R
ISET
= 66.6kW
V
ISET
<
0.4V
I
FB
_ = 30mA
I
FB
_ = 20mA
I
FB
_ = 15mA
I
FB
_ = 30mA
V
FB
_ = 50mV
Full-Scale FB_ Output Current
Current Regulation Between
Strings
Minimum FB_ Regulation Voltage
FB_ On-Resistance
FB_ On-Time
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Maxim Integrated
│
5
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