Simplified Operating Circuit appears at end of data sheet.
●Notebook, Subnotebook,
and Tablet Computer
Displays
●Handy Terminals
General Description
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.
Applications
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
19-4562; Rev 2; 9/14
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
PART TEMP RANGE PIN-PACKAGE
MAX17105ETG+ -40°C to +85°C 24 TQFN-EP*
23
24
22
21
8
7
9
ISET
OSC
OVP
VCC
10
COMP
FB8
FB6
FB5
PGND
FB4
1 2
SCL
4 5 6
1718 16 14 13
SDA
DFSET
FB1
SGND
FAULT
IN
PWMO FB7
3
15
EN
20 11 FB2
PWMI
19 12 FB3
LX
THIN QFN
4mm x 4mm
TOP VIEW
MAX17105
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Pin Conguration
Ordering Information
EVALUATION KIT AVAILABLE
FAULT, IN to SGND ..............................................-0.3V to +30V
FB_, LX to PGND ..................................................-0.3V to +45V
PGND to SGND ....................................................-0.3V to +0.3V
VCC, EN, PWMI, SDA, SCL to SGND ....................-0.3V to +6V
COMP, ISET, OSC, OVP,
PWMO, DFSET to SGND......................... -0.3V to (VCC + 0.3V)
LX Switch Maximum Continuous RMS Current ...................1.6A
Continuous Power Dissipation (TA = +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
(Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kΩ, RISET = 50kΩ, ROSC = 100kΩ, RDFSET = 250kΩ, PWMI = SGND,
CPWMO = 1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
SUPPLY
IN Input Voltage Range (Note 1)
VCC = open, EN = high 5.5 28
V
EN = SGND, SMBus mode
(Note 5)
All functions available 6.3 28
SMBus interface only 3.9 4.0
IN Input Voltage UVLO Threshold
(SMBus Mode Only) (Note 4)
Rising edge, hysteresis = 150mV 5.9 6.05 6.2 V
Falling edge, hysteresis = 150mV 5.75 5.9 6.05
IN Quiescent Current
MAX17105 is enabled at minimum brightness, in
SMBus mode and no-load, VIN = 28V 2.0 3.0 mA
MAX17105 is enabled in SMBus mode and is under IN
UVLO, VIN = 5.5V 0.7 1.1 mA
MAX17105 is disabled 30 60 µA
VCC Output Voltage
MAX17105 is enabled, 6V < VIN < 28V, 0 < IVCC <
10mA 4.7 5.0 5.3 V
MAX17105 is disabled, VIN = 12V 3.7 4.6 4.95
VCC Current Limit VCC is forced to 4.5V 15 40 70 mA
VCC UVLO Threshold Rising edge, typical hysteresis = 85mV 4.00 4.3 4.45 V
STEP-UP REGULATOR
LX On-Resistance 100mA from LX to PGND 0.15 0.3 W
LX Leakage Current 40V on LX, TA = +25°C 1 µA
Operating Frequency
ROSC = 50kW1.7 2.0 2.3
MHz
ROSC = 100kW0.9 1.0 1.1
ROSC = 200kW0.4 0.5 0.6
Minimum On-Time (Note 1) 50 ns
Maximum Duty Cycle At fSW = 1MHz 93 95 97 %
Minimum Off-Time 50 ns
www.maximintegrated.com Maxim Integrated
│
2
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics
Absolute Maximum Ratings
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.
(Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kΩ, RISET = 50kΩ, ROSC = 100kΩ, RDFSET = 250kΩ, PWMI = SGND,
CPWMO = 1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
LX Current Limit Duty cycle = 75% (Note 1) 2.4 2.9 3.4 A
CONTROL INPUT
Logic-Input High Level SDA, SCL, PWMI, EN 2.1 V
Logic-Input Low Level SDA, SCL, PWMI, EN 0.8 V
INPUT LEAKAGE
PWMI Leakage Current TA = +25°C -0.1 +0.1 µA
Logic Input Bias Current TA = +25°C, EN, SDA, SCL -1 +1 µA
OVP Leakage Current TA = +25°C -0.1 +0.1 µA
SDA Output-Low Sink Current VSDA = 0.4V 4 mA
LED CURRENT
Full-Scale FB_ Output Current-
Adjustable Range (Note 4)
PWM-only dimming mode 15 30 mA
SMBus-enabled dimming modes 15 25
Full-Scale FB_ Output Current
RISET = 33.3kW29.1 30.0 30.9
mA
RISET = 50.0kW19.4 20.0 20.6
RISET = 66.6kW14.45 15.0 15.55
VISET < 0.4V 0.2 0.3 0.4
ISET Output Voltage 1.1 1.2 1.3 V
Current Regulation Between
Strings
IFB_ = 30mA -2.0 +2.0
%IFB_ = 20mA -2.0 +2.0
IFB_ = 15mA -2.0 +2.0
Minimum FB_ Regulation
Voltage
IFB_ = 30mA 770
mVIFB_ = 20mA 480
IFB_ = 15mA 450
FB_ On-Resistance VFB_ = 50mV 15 26 W
FB_ Leakage Current VFB_ = 40V, TA = +25°C 0.1 5 µA
FB_ On-Time 400 ns
FAULT PROTECTION
OVP Threshold Voltage Rising edge, hysteresis = 60mV 1.15 1.25 1.35 V
OVP Shutdown Voltage Rising edge 1.35 V
OVP Global Fail 48 120 mV
FB_ UVLO Threshold FB open 140 220 300 mV
FB_ Overvoltage Threshold 7.4 8 8.6 V
FB_ Check LED Source Current 0.4 mA
FB_ Check LED Time 1 ms
www.maximintegrated.com Maxim Integrated
│
3
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kΩ, RISET = 50kΩ, ROSC = 100kΩ, RDFSET = 250kΩ, PWMI = SGND,
CPWMO = 1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
FB_ Overvoltage Fault Timer 88 128 168 µs
Thermal-Shutdown Threshold (Note 1) +150 °C
Overcurrent FAULT Shutdown Timer IPEAK > 2.9A at duty = 75% 72 128 168 µs
FAULT High-Level Leakage Current VFAULT = VIN = 28V, TA = +25°C 1 µA
FAULT Low-Level Clamp Voltage VIN –
5.5
VIN -
5
VIN –
4.5 V
FAULT Charge Current 45 65 µA
PWM FILTER
PWM Output Impedance 20 40 60 kW
DPWM Oscillator Frequency
RDFSET = 500kW100 Hz
RDFSET = 250kW190 200 210
RDFSET = 25kW2kHz
RDFSET = 10kW4.4 5.0 5.5
DFSET Short-Detection
Threshold Voltage 210 300 mV
DFSET Source Current
RDFSET = 500kW4.15
µA
RDFSET = 250kW7.85
RDFSET = 25kW40
RDFSET = 10kW55
PWMI Input Frequency Range DPST/SMBus mode 9.5 10.0 10.5 kHz
Direct-PWM mode 0.1 30.0
PWMI Brightness Setting
SMBus mode, PWMI duty cycle = 98% 97.5 98 98.5
%SMBus mode, PWMI duty cycle = 50% 48 50 52
SMBus mode, PWMI duty cycle = 0% 0.2 0.4 0.6
SMBus TIMING SPECIFICATION
SMBus Frequency fSMB 10 100 kHz
Bus Free Time tBUF 4.7 µs
START Condition Hold Time from SCL tHD:STA 4 µs
START Condition Setup Time from SCL tSU:STA 4.7 µs
STOP Condition Setup Time from SCL tSU:STO 4 µs
SDA Hold Time from SCL tHD:DAT 300 ns
SDA Setup Time from SCL tSU:DAT 250 ns
SCL Low Period tLOW 4.7 µs
SCL High Period tHIGH 4 µs
www.maximintegrated.com Maxim Integrated
│
4
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics (continued)
(Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kΩ, RISET = 50kΩ, ROSC = 100kΩ, RDFSET = 250kΩ, PWMI = SGND,
CPWMO = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
SUPPLY
IN Input Voltage Range (Note 1)
VCC = open, EN = high (Note 5) 5.5 28
V
EN = SGND, SMBus mode All functions available 6.3 28
SMBus interface only 3.9 4.0
IN Input Voltage UVLO
Threshold (SMBus Mode Only)
(Note 2)
Rising edge, hysteresis = 150mV 5.9 6.2
V
Falling edge, hysteresis = 150mV 5.75 6.05
IN Quiescent Current
MAX17105 is enabled at minimum brightness,
in SMBus mode and no load, VIN = 28V 3.0
mA
MAX17105 is enabled in SMBus mode, and is under
IN UVLO, VIN = 5.5V 1.1
MAX17105 is disabled 60 µA
VCC Output Voltage MAX17105 is enabled, 6V < VIN < 28V, 0 < IVCC < 10mA 4.7 5.3 V
MAX17105 is disabled, VIN = 12V 3.7 4.95
VCC Current Limit VCC is forced to 4.5V 15 70 mA
VCC UVLO Threshold Rising edge, typical hysteresis = 85mV 4.00 4.45 V
STEP-UP REGULATOR
LX On-Resistance 100mA from LX to PGND 0.3 W
Operating Frequency
ROSC = 50kW1.7 2.3
MHzROSC = 100kW0.9 1.1
ROSC = 200kW0.45 0.6
Maximum Duty Cycle At fSW = 1MHz 93 98 %
LX Current Limit Duty cycle = 75% 2.4 3.4 A
CONTROL INPUT
Logic-Input High Level SDA, SCL, PWMI, EN 2.1 V
Logic-Input Low Level SDA, SCL, PWMI, EN 0.8 V
SDA Output-Low Sink Current VSDA = 0.4V 4 mA
SDA, SCL Input Bias Current TA = +25NC -1 +1 µA
LED CURRENT
Full-Scale FB_ Output Current
Adjustable Range (Note 3)
PWM only dimming mode 15 30 mA
SMBus-enabled dimming modes 15 25
Full-Scale FB_ Output Current
RISET = 33.3kW28.8 31.2
mA
RISET = 50.0kW18.9 21
RISET = 66.6kW14.25 15.75
VISET < 0.4V 0.2 0.4
Current Regulation Between
Strings
IFB_ = 30mA -2.5 +2.5
%IFB_ = 20mA -2.5 +2.5
IFB_ = 15mA -2.5 +2.5
Minimum FB_ Regulation Voltage IFB_ = 30mA 770 mV
FB_ On-Resistance VFB_ = 50mV 26 W
FB_ On-Time 400 ns
www.maximintegrated.com Maxim Integrated
│
5
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics
(Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kΩ, RISET = 50kΩ, ROSC = 100kΩ, RDFSET = 250kΩ, PWMI = SGND,
CPWMO = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER CONDITIONS MIN TYP MAX UNITS
FAULT PROTECTION
OVP Threshold Voltage Rising edge, hysteresis = 60mV 1.15 1.35 V
OVP Shutdown Voltage Rising edge (tracks with OVP threshold voltage) 1.25 1.45 V
OVP Global Fail 48 120 mV
FB_ UVLO Threshold FB open 140 300 mV
FB_ Overvoltage Threshold 7.4 8.6 V
FB_ Check LED Source Current 0.4 mA
FB_ Overvoltage Fault Timer 88 168 µs
Overcurrent FAULT Shutdown Timer IPEAK > 2.9A at duty = 75% (typical) 72 168 µs
FAULT High-Level Leakage Current VFAULT = VIN = 28V 1 µA
FAULT Low-Level
Clamp Voltage
VIN –
5.5
VIN –
4.5 V
FAULT Charge Current 45 65 µA
PWM FILTER
PWM Output Impedance 20 60 kI
DPWM Oscillator Frequency RDFSET = 250kW190 210 Hz
RDFSET = 10kW4.4 5.5 kHz
DFSET Short-Detection
Threshold Voltage 300 mV
PWMI Input Frequency Range DPST/SMBus mode 9.5 10.5 kHz
Direct-PWM mode 0.1 30.0
PWMI Brightness Setting
SMBus mode, PWMI duty cycle = 98% 97.5 98.5
%SMBus mode, PWMI duty cycle = 50% 48 52
SMBus mode, PWMI duty cycle = 0% 0.2 0.6
SMBus TIMING SPECIFICATION
SMBus Frequency fSMB 10 100 kHz
Bus Free Time tBUF 4.7 µs
START Condition Hold Time from SCL tHD:STA 4 µs
START Condition Setup Time from SCL tSU:STA 4.7 µs
STOP Condition Setup Time from SCL tSU:STO 4 µs
SDA Hold Time from SCL tHD:DAT 300 ns
SDA Setup Time from SCL tSU:DAT 250 ns
SCL Low Period tLOW 4.7 µs
SCL High Period tHIGH 4 µs
www.maximintegrated.com Maxim Integrated
│
6
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Electrical Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
Note 1: Specifications are guaranteed by design, not production tested.
Note 2: Specifications to TA = -40°C are guaranteed by design, not production tested.
Note 3: LED full-scale current maximum value is subjected to string number, LED number per string, and LX current limit. In SMBus
modes, if the total load is heavier than 8 strings with 10 WLEDs per string at 25mA LED current, upon step-up regulator
input VS removal, an OC fault may occur, resulting in SMBus status register OV_CURR and FAULT bits being set to 1 and
violating SMBus specifications.
Note 4: Minimum voltage drop from VS to IN pin, including the forward voltage drop of diode DIN1 used in Figure 1, should be
no less than 0.8V. If lower forward voltage drop diode is used, upon step-up regulator input VS removal, an OC fault may
occur, resulting in SMBus status register OV_CURR and FAULT bits being set to 1 and violating SMBus specifications.
Note 5: Dimming modes not to be done after the driver starts up or on-the-fly.
Circuit of Figure 1. VIN = 12V, CCOMP = 33nF, RCOMP = 1kW, RISET = 50kW, ROSC = 100kW, RDFSET = 250kW, PWMI = SGND,
CPWMO = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
LED CURRENT
vs. BRIGHTNESS SETTING
PWM DUTY CYCLE (%)
LED CURRENT (mA)
40 60 80 100
20
5
15
10
20
0
0
MAX17105 toc03
DIRECT-PWM MODE
BOOST CONVERTER EFFICIENCY
vs. BRIGHTNESS
(VS = 12V, VOUT = 32V/IOUT
= 160mA AT 100%)
BRIGHTNESS (%)
EFFICIENCY (%)
40 60 80 100
20
60
80
70
90
50
0
MAX17105 toc02
DirectPWM MODE WITHOUT
EXTERNAL p-CHANNEL MOSFET
BOOST CONVERTER EFFICIENCY
vs. INPUT VOLTAGE (VS)
(VOUT = 32V/IOUT
= 160mA, BRIGHTNESS = 100%)
INPUT VOLTAGE (V)
EFFICIENCY (%)
13 16 19 22
10
87
86
89
88
91
90
85
84
7
MAX17105 toc01
WITHOUT EXTERNAL p-CHANNEL MOSFET
Maxim Integrated
│
7
www.maximintegrated.com
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Typical Operating Characteristics
Electrical Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
SWITCHING WAVEFORMS
(VS = 7V, BRIGHTNESS = 100%)
1µs/divW
VLX
20V/div
INDUCTOR
CURRENT
500mA/div
0A
0V
MAX17105 toc09
IN SHUTDOWN CURRENT
vs. IN VOLTAGE
IN VOLTAGE (V)
SHUTDOWN CURRENT (°A)
13 16 19 22
10
32
26
23
29
35
20
7
MAX17105 toc08
DIRECT-PWM MODE
SMBus MODE
IN QUIESCENT CURRENT
vs. IN VOLTAGE
IN VOLTAGE (V)
QUIESCENT CURRENT (mA)
13 16 19 22
10
1
5
3
2
4
6
0
7
MAX17105 toc07
SMBus = 0
SMBus = 255
LED CURRENT
vs. INPUT VOLTAGE
INPUT VOLTAGE (V)
LED CURRENT (mA)
13 16 19 22
10
5
20
10
15
25
0
7
MAX17105 toc06
BRIGHTNESS = 10%
DIRECT-PWM MODE
BRIGHTNESS = 100%
LED CURRENT
vs. PWMI DUTY CYCLE
PWMI DUTY CYCLE
LED CURRENT (mA)
40 60 80 100
20
5
15
10
20
0
0
MAX17105 toc05
SMBus = 128
DPST MODE
SMBus = 255
LED CURRENT
vs. SMBus BRIGHTNESS SETTING
SMBus BRIGHTNESS SETTING
LED CURRENT (mA)
100 150 200 250
50
5
15
10
20
0
0
MAX17105 toc04
SMBus MODE
Maxim Integrated
│
8
www.maximintegrated.com
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
LED-OPEN FAULT PROTECTION
(BRIGHTNESS = 100%, LED OPEN ON FB1)
400µs/div
VOUT
20V/div
VFB1
1V/div
0V
0V
0V
VFB2
10V/div
IFB2
20mA/div
0A
MAX17105 toc15
LED CURRENT WAVEFORMS
(BRIGHTNESS = 1%)
2ms/div
INDUCTOR CURRENT
1A/div
VOUT
20V/div
VFB1
10V/div
0V
0V
IFB1
20mA/div
0A
0A
MAX17105 toc14
DIRECT-PWM MODE
LED CURRENT WAVEFORMS
(BRIGHTNESS = 50%)
2ms/div
INDUCTOR CURRENT
500mA/div
VOUT
20V/div
VFB1
10V/div
0V
0V
ILED
20mA/div
0A
0A
MAX17105 toc13
STARTUP WAVEFORMS
(BRIGHTNESS = 20%)
2ms/div
VLX
20V/div
VOUT
20V/div
VEN
5V/div
0V
0V
VFAULT
10V/div
0V
0V
MAX17105 toc12
DIRECT-PWM MODE
STARTUP WAVEFORMS
(BRIGHTNESS = 100%)
2ms/div
VLX
20V/div
VOUT
20V/div
VEN
5V/div
0V
0V
VFAULT
10V/div
0V
0V
MAX17105 toc11
DIRECT-PWM MODE
SWITCHING WAVEFORMS
(VS = 24V, BRIGHTNESS = 100%)
1µs/div
VLX
20V/div
0V
INDUCTOR
CURRENT
500mA/div
0A
MAX17105 toc10
Maxim Integrated
│
9
www.maximintegrated.com
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
LED CURRENT BALANCE
vs. INPUT VOLTAGE
INPUT VOLTAGE (V)
LED CURRENT BALANCE (%)
13 1916 22
10
0.9
0.7
0.6
0.8
1.0
0.5
7
MAX17105 toc20
LED CURRENT BALANCE
vs. BRIGHTNESS
BRIGHTNESS (%)
LED CURRENT BALANCE (%)
30 5040 7060 90 10080
20
1.2
0.4
0.8
1.6
0
10
MAX17105 toc19
DIRECT-PWM MODE
LINE-TRANSIENT RESPONSE
(VS = 21V ➝ 9V, BRIGHTNESS = 100%)
200µs/div
VOUT
20V/div
0A
0V
0V
VS
10V/div
IFB1
20mA/div
INDUCTOR CURRENT
1A/div
0A
MAX17105 toc18
LINE-TRANSIENT RESPONSE
(VS = 9V ➝ 21V, BRIGHTNESS = 100%)
200µs/div
INDUCTOR CURRENT
1A/div
VOUT
20V/div
0A
0A
0V
0V
VS
10V/div
IFB1
20mA/div
MAX17105 toc17
LED-SHORT FAULT PROTECTION
(BRIGHTNESS = 100%, 3LEDs SHORT ON FB1)
400µs/div
IFB1
50mA/div
VFB1
10V/div
0A
0V
0V
VFB2
5V/div
IFB2
50mA/div
0A
MAX17105 toc16
Maxim Integrated
│
10
www.maximintegrated.com
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Typical Operating Characteristics (continued)
PIN NAME FUNCTION
1 COMP
Step-Up Regulator Compensation Pin. Connect a 0.033µF ceramic capacitor and 1kW resistor from
COMP to SGND and an additional 220pF capacitor from COMP to SGND. When the MAX17105
shuts down, COMP is discharged to 0V through an internal 20kΩ resistor.
2 ISET
Full-Scale LED Current Adjustment Pin. The resistance from ISET to SGND controls the full-scale
current in each LED string:
ILED_MAX = 20mA x 50kΩ/RISET
The acceptable resistance range is 33.3kΩ < RISET < open, which corresponds to full-scale LED
current of 30mA > ILED_MAX > 0mA. Connecting ISET to SGND sets the test mode for 0.3mA (typ)
full-scale LED current.
3 PWMO
Filtered PWM Signal Output. Connect a capacitor between PWMO and SGND. The capacitor forms
a lowpass lter with an internal 40kΩ (typ) resistor to lter the PWM signal into an analog signal
whose level represents the duty cycle information of the input PWM signal.
4 OSC
Oscillator Frequency Adjustment Pin. The resistance from OSC to SGND sets the step-up
regulator’s oscillator frequency:
fSW = 1MHz x 100kΩ/ROSC
The acceptable resistance range is 50kΩ < ROSC < 200kΩ, which corresponds to the switching
frequency of 2MHz > fSW > 500kHz.
5 OVP Overvoltage Sense. Connect OVP to the center tap of a resistive voltage-divider from the output of
the step-up regulator to ground.
6 VCC 5V Linear-Regulator Output. VCC provides power to the MAX17105. Bypass VCC to SGND with a
ceramic capacitor of 1µF or greater.
7 IN Power-Supply Input. VIN biases the internal 5V linear regulator that powers the device. Bypass IN to
SGND directly at the pin with a 0.1µF ceramic capacitor or greater.
8 FAULT
External p-Channel MOSFET Gate Drive-Output. External pullup resistor is connected between
FAULT and IN when p-channel MOSFET is used. If the p-channel MOSFET is not used, leave
FAULT unconnected.
9 SGND Analog Ground
10 FB1 LED String 1 Cathode Connection. FB1 is the open-drain output of an internal regulator, which
controls current through FB1. FB1 can sink up to 30mA. If unused, connect FB1 to SGND.
11 FB2 LED String 2 Cathode Connection. FB2 is the open-drain output of an internal regulator, which
controls current through FB2. FB2 can sink up to 30mA. If unused, connect FB2 to SGND.
12 FB3 LED String 3 Cathode Connection. FB3 is the open-drain output of an internal regulator, which
controls current through FB3. FB3 can sink up to 30mA. If unused, connect FB3 to SGND.
13 FB4 LED String 4 Cathode Connection. FB4 is the open-drain output of an internal regulator, which
controls current through FB4. FB4 can sink up to 30mA. If unused, connect FB4 to SGND.
14 FB5 LED String 5 Cathode Connection. FB5 is the open-drain output of an internal regulator, which
controls current through FB5. FB5 can sink up to 30mA. If unused, connect FB5 to SGND.
15 FB6 LED String 6 Cathode Connection. FB6 is the open-drain output of an internal regulator, which
controls current through FB6. FB6 can sink up to 30mA. If unused, connect FB6 to SGND.
16 FB7 LED String 7 Cathode Connection. FB7 is the open-drain output of an internal regulator, which
controls current through FB7. FB7 can sink up to 30mA. If unused, connect FB7 to SGND.
17 FB8 LED String 8 Cathode Connection. FB8 is the open-drain output of an internal regulator, which
controls current through FB8. FB8 can sink up to 30mA. If unused, connect FB8 to SGND.
www.maximintegrated.com Maxim Integrated
│
11
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Pin Description
PIN NAME FUNCTION
18 PGND Step-Up Regulator Power Ground
19 LX Step-Up Regulator Switching Node. Drain of the internal n-channel MOSFET between LX and
PGND. Connect the inductor and catch diode here and minimize trace area for lowest EMI.
20 PWMI
PWM Signal Input. This PWM signal is used for brightness control in direct-PWM mode or DPST mode of
SMBus mode. In direct-PWM mode, the DPWM duty cycle is equal to the input PWM duty cycle. In DPST
mode, the DPWM duty cycle is the input PWM duty cycle multiplied by the SMBus brightness command.
PWMI directly controls the LED current source on or off in direct-PWM mode.
21 EN Direct-PWM Mode Enable Pin. When direct-PWM mode is selected through the DFSET pin, the
MAX17105 can start up with direct-PWM mode by EN = high.
22 SCL SMBus Serial Clock Input
23 SDA SMBus Serial Data Input
24 DFSET
DPWM Frequency Adjustment Pin. Connect a resistor from DFSET to SGND to set the internal
DPWM frequency in SMBus mode. In direct-PWM mode, DFSET pin is connected to SGND:
fDPWM = 200Hz x 250kΩ/RDFSET
The acceptable resistance range is 10kΩ < RDFSET < 500kΩ, which corresponds to the DPWM
frequency of 5kHz > fDPWM > 100Hz.
— EP Exposed Backside Pad. Solder to the circuit board ground plane with sufcient copper connection to
ensure low thermal resistance. See the PCB Layout Guidelines section.
www.maximintegrated.com Maxim Integrated
│
12
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Pin Description (continued)
Detailed Description
The MAX17105 typical operating circuit is shown in
Figure 1. Table 1 lists some recommended components,
and Table 2 lists the contact information of component
suppliers.
Table 2. Component SuppliersTable 1. Component List
Figure 1. Typical Operating Circuit
SUPPLIER PHONE WEBSITE
Fairchild
Semiconductor 888-522-5372 www.fairchildsemi.com
Murata 770-436-1300 www.murata-northamerica.com
Nichia Corp. 248-352-6575 www.nichia.com
TDK Corp. 847-803-6100 www.component.tdk.com
Toshiba
America
Electronic
Components,
Inc.
949-623-2900 www.toshiba.com/taec
Vishay 402-563-6866 www.vishay.com
DESIGNATION DESCRIPTION
White LED Nichia NSSW008C 3.2V (typ), 3.5V
(max) at 20mA
L1 10µH, 1.5A, H = 1.2mm
TDK VLP6812T-100M1R5
Q1 (Optional)
30V, 65mW p-channel MOSFET
Si3481DV
FDC658AP
CIN
4.7µF ±10%, 25V X5R ceramic
capacitor (1206)
Murata GRM319R61E475KA12D
C1, C2
2.2µF ±20%, 50V X7R ceramic
capacitors (1206)
Murata GRM31CR71H225K
D1 2A, 40V Schottky diode (M-flat)
Toshiba CMS11
FB1
PGND
IN FAULT
RCOMP
5.1kΩ
D1
Q1
P
OPTIONAL L1
10µH
LX
R1
2.21MΩ
REXT
200kΩ
CIN
4.7µF
DIN1
0.1µF
VCCA 5V
VS
7V TO 24V
CPWMO
1µF
ROSC
100kΩ
RISET
50kΩRDFSET
250kΩ
CCOMP2
0.022µF
CCOMP1
220µF
1µF
SMBus
INTERFACE
C2
2.2µF
R2
71.5kΩ
OVP
FB2
FB3
FB4
FB5
FB6
FB7
FB8
ISET
VCC
PWMI
PWMO
10kHz
MAX17105
DFSET
EN
SCL
SDA
OSC
COMP
EP
C1
2.2µF
SGND
www.maximintegrated.com Maxim Integrated
│
13
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
The MAX17105 is a high-efficiency driver for arrays of white
LEDs. It contains a fixed-frequency, current-mode PWM
step-up controller, a 5V linear regulator, dimming control cir-
cuit, SMBus interface, internal power MOSFET, eight regu-
lated current sources, and an external p-channel MOSFET
drive circuit. Figure 2 shows the MAX17105 functional
diagram. When enabled, the step-up controller boosts the
output voltage to provide sufficient headroom for the cur-
rent sources to regulate their respective string currents.
The MAX17105 features a resistor-adjustable switching fre-
quency (500kHz to 2MHz), which allows trade-offs between
external component size and operating efficiency.
Figure 2. Functional Diagram
5V LINEAR
REGULATOR
OSCILLATOR SLOPE
COMPENSATION
OVERVOLTAGE
COMPARATOR
ERROR
COMPARATOR
OUTPUT OVERVOLTAGE
COMPARATOR
OVP
LX
N
N
PGND
ERROR
COMPARATOR
IN
FB1
SGND
FB2
FAULT
CONTROL
TO FAULT
CONTROL
CONTROL AND
DRIVER LOGIC
CURRENT SENSE
HVC FB6
FB5
FB4
FB3
FB2
LVC
Gm
FB7
FB8
EN
VCC
OSC
FAULT
ISET
8V
1.25V
1.35V
ISET
EN
PWMO
PWMI
SDA
SMBus CONTROL
AND
DPWM GENERATOR
VSAT
DPWM CONTROL SIGNAL
CURRENT SOURCE
SCL
DFSET
COMP
VCC
FB3
CURRENT SOURCE
FB4
CURRENT SOURCE
FB5
CURRENT SOURCE
FB6
CURRENT SOURCE
FB7
CURRENT SOURCE
FB8
CURRENT SOURCE
MAX17105
www.maximintegrated.com Maxim Integrated
│
14
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
WLED brightness is controlled by turning the WLEDs on
and off with a DPWM signal. The DPWM frequency can
be accurately adjusted with a resistor or directly controlled
by the PWMI signal. The brightness of the LEDs is pro-
portional to the duty cycle of the DPWM signal, which
is controlled externally through either a PWM or 2-wire
SMBus-compatible interface, or both. When both inter-
faces are used at the same time, the product of the PWM
duty cycle and SMBus command value is used for the
dimming control. This DPWM control provides a dimming
range with 8-bit resolution.
The MAX17105 has multiple features to protect the
controller from fault conditions. Separate feedback
loops limit the output voltage in all circumstances. The
MAX17105 checks each FB_ voltage during the opera-
tion. If one or more strings are open, the corresponding
FB_ voltages are pulled below 220mV (typ), and an
open-circuit fault is detected. As a result, the respective
current sources are disabled. When one or more LEDs
are shorted and the FB_ voltage exceeds 8V, a short
fault is detected and the respective current source is
disabled. In either LED open or short conditions, the fault
strings are disabled while other strings can still operate
normally. The controller features cycle-by-cycle current
limit to provide consistent operation and soft-start pro-
tection. In a current-limit condition, the controller shuts
down after a 128µs overcurrent fault timer expires. A
thermal-shutdown circuit provides yet another level of
protection.
The MAX17105 includes a 5V linear regulator that pro-
vides the internal bias and gate driver for the step-up
controller.
Fixed-Frequency Step-Up Controller
The MAX17105’s fixed-frequency, current mode, step-up
controller automatically chooses the lowest active FB_
voltage to regulate the feedback voltage. Specifically,
the difference between the lowest FB_ voltage and the
current source control signal plus an offset (VSAT) is
integrated at the COMP output. The resulting error signal
is compared to the external switch current plus slope
compensation to determine the switch on-time. As the
load changes, the error amplifier sources or sinks current
to the COMP output to deliver the required peak inductor
current. The slope-compensation signal is added to the
current-sense signal in order to improve stability at high
duty cycles.
Internal 5V Linear Regulator and UVLO
The MAX17105 includes an internal low-dropout (LDO)
linear regulator (VCC). When VIN is higher than 5.5V,
this linear regulator generates a 5V supply to power
the internal PWM controller, control logic, and MOSFET
driver. The VCC voltage drops to 4.5V in standby. If VIN is
less than or equal to 5.5V, VCC and IN can be connected
together and powered from an external 5V supply. There
is a body diode from VCC to IN, so VIN must be greater
than VCC. (See Figure 2.)
The MAX17105 includes power-on reset (POR) and
undervoltage lockout (UVLO) features. POR resets the
fault latch and sets all the SMBus resisters to their POR
values. POR occurs when VCC rises above 2.8V (typ).
The controller is disabled until VCC exceeds the UVLO
threshold of 4.3V (typ). The hysteresis on VCC UVLO is
approximately 85mV.
In standby mode, the internal LDO is low-power mode
with 60µA (max) input current and regulated at 4.5V (typ).
When EN is high in direct-PWM mode or an ENABLE
command through the SMBus interface, the internal LDO
is enabled and regulated at 5.0V (typ). In addition to VCC
UVLO, the MAX17105 has also implemented an IN UVLO
function. This IN UVLO function is not activated in direct-
PWM mode. However, when the controller is enabled with
SMBus, the IN UVLO feature is enabled. If the IN voltage
is below its UVLO threshold, the step-up converter is shut
off.
The VCC pin should be bypassed to SGND with a mini-
mum 1µF ceramic capacitor.
Startup
The MAX17105 has two operating modes: direct-PWM
mode and SMBus mode. The two modes are identified
by the DFSET pin. At the first enable signal, either EN =
high or an SMBus ENABLE command, the DFSET pin
sources a current to check whether the DFSET pin is
connected to SGND. When the DFSET voltage is lower
than 210mV (typ), the MAX17105 is set for direct-PWM
mode. Otherwise, the MAX17105 is set for SMBus mode.
Once the mode is set, the mode is not cleared until the
VCC is lower than the POR voltage. When the MAX17105
is set for SMBus mode, the EN pin signal is ignored
and the MAX17105 is woken by the SMBus ENABLE
command. When the MAX17105 is set for direct-
PWM mode, the SMBus command is ignored and the
MAX17105is woken by the EN signal. Table 3 summa-
rizes the operating mode.
www.maximintegrated.com Maxim Integrated
│
15
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
At startup, there are three phases. The first phase is
p-channel MOSFET soft-start time, the second is check
LED time (1ms), and the last phase is boost soft-start
time (4ms). In the first phase, FAULT sink current is
increased from 0µA to 50µA to avoid high inrush current
caused by the p-channel MOSFET turn-on. In check LED
time, the MAX17105 performs a diagnostic test of the
LED array. In the test phase, all FB_ are pulled up by
0.8mA (typ, 0.4mA min) current source during 1ms (typ). If
some FB_ voltage is lower than 1.2V (max), the string is
considered to be unused. Therefore, when a string is not
in use, it should be connected to SGND. All other strings
with FB_ higher than 1.2V (max) are detected as in use.
After the LED string diagnostic phases are finished, the
step-up regulator starts. The total startup time is less than
10ms. Figure 3 shows the sequence.
Standby and FAULT Shutdown
The MAX17105 can be placed into standby by EN = low
in direct-PWM mode or clearing bit 0 of the device control
register (0x01) in SMBus mode. When a critical failure is
detected, the IC enters fault shutdown mode. In standby
or fault shutdown mode, all functions of the IC are turned
off, including the 5V linear regulator. Only a crude linear
regulator remains on providing a 4.5V (typ) output voltage
to VCC, with 1µA current sourcing capability. The Fault/
Status register is not reset in fault shutdown. When bit 0
of the device control register (0x01) is set to 1 in SMBus
mode or cycling the EN pin, the MAX17105 exits fault
shutdown mode and starts. The Fault/Status register is
reset at startup.
Figure 3. Startup Timing Sequence
X = Don’t Care
Table 3. Operating Mode
EN DFSET SCL, SDA
Direct PWM
(Standby) Low SGND X
Direct PWM
(Startup) High SGND X
SMBus
(Standby) X RDFSET CLOCK
SMBus
(Startup) X RDFSET
ENABLE
Command
VVCC
VFAULT
VOUT
IFAULT
0uA
PFET
SOFT-START
STEP-UP REGULATOR
SOFT-START
CHECK LED
VIN
0V
0V
0V
0V
www.maximintegrated.com Maxim Integrated
│
16
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
In standby or fault shutdown, the FAULT pin is pulled up to
IN with an internal resistor of 1MW (typ), and the p-chan-
nel MOSFET is turned off. An external resistor could be
used as well (REXT > 200kW).
Frequency Selection
The step-up regulator switching frequency can be adjust-
ed through the external resistor-connected OSC pin. The
switching frequency adjustable range is 500kHz to 2MHz.
High-frequency (2MHz) operation optimizes the regulator
for the smallest component size, at the expense of effi-
ciency due to increased switching losses. Low-frequency
(500kHz) operation offers the best overall efficiency, but
requires larger components and PCB area. The maximum
step-up regulator duty is limited by the 50ns (typ) mini-
mum on-time.
Overvoltage Protection
To protect the step-up regulator when the load is open, or
the output voltage becomes excessive for any reason, the
MAX17105 features a dedicated overvoltage feedback
input (OVP). The OVP pin is connected to the center tap
of a resistive voltage-divider from the high-voltage output.
The OVP pin has two levels of threshold. When the OVP
pin voltage, VOVP, exceeds 1.25V (typ), a compara-
tor turns off the internal power MOSFET and prevents
excessive voltage from damage. This step-up regulator
switch is reenabled after the VOVP drops 60mV (typ) hys-
teresis below the protection threshold. This overvoltage-
protection feature ensures the step-up regulator fail-safe
operation when the LED strings are disconnected from
the output. When the OVP pin voltage exceeds 1.35V
(typ), the IC is in fault shutdown.
LED Current Sources
Maintaining uniform LED brightness and dimming capabil-
ity are critical for backlight applications. The MAX17105 is
equipped with a bank of eight matched current sources.
These specialized current sources are accurate to within
±2%, and can be switched on- and off-PWM frequencies
of up to 30kHz in direct-PWM mode and 5kHz in SMBus
mode. All LED full-scale currents are identical and are set
through the ISET pin (0mA < ILED < 30mA). The LED cur-
rent source has high-speed capability and allows 400ns
minimum on-time within 400ns rise and fall time.
The minimum voltage drop across each current source
is 500mV (max) when the LED current is 20mA. The low
voltage drop helps reduce dissipation while maintaining
sufficient compliance to control the LED current within the
required tolerances.
The LED current sources can be disabled by connecting
the respective FB_ pin to SGND at startup. When the IC
is enabled, the controller scans settings for all FB_ pins.
If a FB_ pin is not connected to SGND, an internal circuit
pulls this pin high, and the controller enables the corre-
sponding current source to regulate the string current. If
the FB_ pin is connected to SGND, the controller disables
the corresponding current regulator. The current regulator
cannot be disabled by connecting the respective FB_ pin
to SGND after the IC is enabled.
All FB_ pins in use are combined to extract a lowest FB_
voltage (LVC) (see Figure 2). LVC is fed into the step-up
regulator’s error amplifier and is used to set the output
voltage.
Current Source Fault Protection
LED fault open/short is detected after startup. When one
or more strings fail after startup, the corresponding cur-
rent source is disabled. The remaining LED strings are
still operated normally. When a fault is detected, bit 4 or/
and bit 5 of the Fault/Status resister are set in SMBus
mode. (See the Fault Status Register description in the
Dimming Control Register Descriptions section.)
LED Short and String Mismatch Protection
The MAX17105 can tolerate slight mismatch between
LED strings. When severe mismatches or WLED shorts
occur, the FB_ voltages are uneven because of mis-
matched voltage drops across strings. At each LED turn-
on, the FB_ voltage is brought down to the regulation
voltage quickly. When FB_ voltage is higher than 8V (typ)
after the LED turns on, the LED short is detected. When
the LED short condition is continued for 2ms, the strings
are disabled. The remaining LED strings can still oper-
ate normally. If only one string is used, the output volt-
age decreases and regulates the needed current during
the operation of LED short. The LED short protection is
not triggered since FB_ voltage is never higher than the
threshold. The LED short protection is disabled during the
soft-start phase of the step-up regulator.
Open-Current Source Protection
The MAX17105 step-up regulator output voltage is regu-
lated according to the minimum FB_ voltages on all of
the strings in use. If one or more strings are open, the
respective FB_ pins are pulled to ground. For any FB_
lower than 220mV, the corresponding current source is
disabled. The remaining LED strings can still operate nor-
mally. If all strings in use are open, the MAX17105 shuts
the step-up regulator down.
www.maximintegrated.com Maxim Integrated
│
17
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Dimming Control
The MAX17105 has two dimming modes that are selected
by the DFSET pin as shown in Table 3. The LED on/off
DPWM frequency is generated by the internal oscillator
for SMBus mode, while LED is directly on/off by the PWMI
pin in direct-PWM mode. The DPWM frequency is adjust-
able through an external setting resistor and has 3%
accuracy over the 200Hz to 2kHz range. In SMBus mode,
the duty cycle of this DPWM signal can be controlled
externally through two interfaces: PWM and SMBus. The
ISET pin sets the amplitude of the current sources for
each LED string (Figure 2). The internal DPWM signal
directly controls the duty cycle of these current sources.
The resulting current is chopped and synchronized to the
DPWM signal. When filtered by the slow response time of
the human eye, the overall brightness is modulated in a
consistent flicker-free manner.
Full-Scale LED and Low-Level LED Current
The full-scale LED current IISET is determined by the
resistors connected from ISET to SGND:
LED_MAX
ISET
20mA 50k
IR
=
OI
The acceptable resistance range is 33.3kW < RISET <
open, which corresponds to full-scale LED current of
30mA > ILED_MAX > 0mA. Connect ISET to SGND sets
the test mode for 0.3mA (typ) full-scale LED current.
DPWM Frequency Setting
The MAX17105 uses an internal DPWM signal to perform
dimming control while operating at SMBus mode. The
DPWM frequency is specified by an external resistor con-
nected from the DFSET pin to SGND:
DPWM DFSET
200Hz 250k
fR
=
OI
The adjustable range for the DFSET resistor, RDFSET,
is from 10kW to 500kW, corresponding to the DPWM fre-
quency of 5kHz > fDPWM > 100Hz.
Dimming Control Interfaces for SMBus Mode
The MAX17105’s dimming control circuit consists of
two interfaces: PWM and SMBus. The block diagram of
these two input interfaces is shown in Figure 4. The dim-
ming can be performed in three modes: PWM, SMBus,
or DPST. In PWM mode, the brightness is adjusted by
the PWM signal applied to the PWMI pin. In SMBus
mode, the brightness is adjusted by an I2C command
from an uplink processor through a 2-wire SMBus. In
DPST mode, the brightness is adjusted by the product
of the PWM duty cycle and SMBus command value. This
DPWM control provides a dimming range with 8-bit reso-
lution down to 0% and supports Intel DPST to maximize
battery life.
The SMBus interface can be used to adjust the dim-
ming, as well as shut down the MAX17105. Before the
MAX17105 receives a turn-on command from the SMBus,
it automatically remains off. In this low-power state, most of
the control circuits are turned off, and only part of the LDO
is active to provide a loosely regulated output of approxi-
mately 4.5V on the VCC pin to power the SMBus interface.
Figure 4. PWM and SMBus Interface Circuit
PWMI
PWMO
BUFFER
AMUX
0x03
IDENTIFICATION
REGISTER
D1
≤ 1
SCL
SMBus
INTERFACE
DPWM
SETTING
DIGITAL
MULTIPLIER
BACKLIGHT
ON/OFF
SDA
0x02 0x01 0x00
MUX
PWM_SEL
PWM_MD
SMBus AND PWM INPUT BLOCK
FAULT/STATUS
REGISTER
DEVICE
CONTROL
REGISTER
BRIGHTNESS
CONTROL
REGISTER
www.maximintegrated.com Maxim Integrated
│
18
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
The MAX17105 uses two multiplexers internally to direct the dimming signal processing (Figure 4). These two multiplex-
ers are controlled by 2 bits of the device control register, PWM_SEL and PWM_MD, respectively. The PWM_SEL bit
selects either the SMBus or the PWMI input to control the brightness. The PWM_MD bit selects the mode in which the
PWMI input is to be interpreted. Table 4 provides a complete setting of the three dimming modes.
Device Control Register: Address is 0x01. This register is both readable and writeable for Bit 0 to Bit 2. Bit 0, also
named BL_CTL, is used as on/off control for the output LEDs. Bit 1 and Bit 2, named PWM_SEL and PWM_MD respec
tively, control the operating mode of the backlight controller. Bit 3 to Bit 7 are reserved bits. All reserved bits, return 0
when read, and are ignored by the controller when written. A value of 1 written to BL_CTL turns on the backlight in 10ms
or less after the write cycle completes. A value of 0 written to BL_CTL immediately turns off the backlight.
Dimming Control Register Descriptions
The MAX17105 includes four registers to monitor and control brightness, fault status, driver ID, and operating mode.
Brightness Control Register: Address is 0x00. This register is both readable and writeable for all 8 bits, and for BRT0,
and BRT7, which are used to control the LED brightness level. In SMBus dimming mode, an SMBus write byte cycle to
register 0x00 sets the output brightness level. The SMBus setting of 0xFF for this register sets the backlight controller to
the maximum brightness output, and 0x00 sets 0.4% backlight brightness. The default value for register 0x00 is 0xFF. A
write byte cycle to register 0x00 has no effect when the backlight controller is in PWM mode. The SMBus read byte cycle
to register 0x00 returns the current brightness level regardless of the dimming mode.
X = Don’t Care
Table 4. Operating Modes Selected by Device Control Register Bits 1 and 2
PWM_MD PWM_SEL MODE DPWM DUTY-CYCLE SETTING
X 1 PWM mode PWMI input duty cycle
1 0 SMBus mode SMBus command
0 0 DPST mode Product of PWMI input duty cycle and SMBus command
REGISTER 0x01 DEVICE CONTROL REGISTER DEFAULT VALUE 0X00
Reserved Reserved Reserved Reserved Reserved PWM_MD PWM_SEL BL_CTL
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 (R/W) Bit 1 (R/W) Bit 0 (R/W)
Bit Field Definitions:
BIT FIELD DEFINITION DESCRIPTION
Bit 2 PWM_MD PWM mode select (1 = absolute brightness, 0 = % change) default = 0
Bit 1 PWM_SEL Brightness MUX select (1 = PWMI pin, 0 = SMBus value) default = 0
Bit 0 BL_CTL BL on/off (1 = On, 0 = Off) default = 0
REGISTER 0x00 BRIGHTNESS CONTROL REGISTER DEFAULT VALUE 0xFF
BRT7 BRT6 BRT5 BRT4 BRT3 BRT2 BRT1 BRT0
Bit 7 (R/W) Bit 6 (R/W) Bit 5 (R/W) Bit 4 (R/W) Bit 3 (R/W) Bit 2 (R/W) Bit 1 (R/W) Bit 0
(R/W)
Bit Field Definitions:
BIT FIELD DEFINITION DESCRIPTION
Bit [7:0] BRT [7:0] 8-bit brightness setting, adjusting brightness levels in 256 steps, default value is 0xFF.
www.maximintegrated.com Maxim Integrated
│
19
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
The list of ID values for vendors is shown below, based on the current backlight controller vendor list and is not sorted
in any particular order.
Identification Register: Address is 0x03. The ID register contains two bit fields to denote the manufacturer and the
silicon revision of the controller IC. The bit field widths were chosen to allow up to 32 vendors with up to eight silicon
revisions each. This register is read only.
In PWM mode, the output LED brightness is solely controlled by the percentage duty cycle of the input signal to
PWMI. In SMBus mode, the input of PWMI has no effect on the dimming control, and only the SMBus command to the
brightness control register adjusts the output brightness. In DPST mode, the overall brightness level is the normalized
product of the SMBus command setting and PWM input duty cycle. The PWM signal starts from 100% when operating
in DPST mode. The default value for register 0x01 is 0x00.
Fault/Status Register: Address is 0x02. This register has 6 status bits that allow monitoring the backlight controller’s
operating state. Bit 6 and Bit 7 are reserved bits, and Bit 3 is the status indicator or backlight. The other 5 bits are fault
indicators. Bit 0 is a logical OR of all fault codes to simplify error detection (GLOBAL FAIL, OVCURR FAIL, 1CH
SHORT/OPEN, 2 CH SHORT/OPEN, THRM_SHDN). All the bits in this register are read only. The reserved bits return
a 0 when read.
Table 5. Vendor IDs
ID VENDOR
5 ST
6Analog Devices
7-14 Reserved
15 Vendor ID register not implemented
ID VENDOR
0 Maxim
1Micro Semi
2 MPS
3O2 Micro
4 TI
REGISTER 0x03 ID REGISTER DEFAULT VALUE 0X80
LED Panel MFG3 MFG2 MFG1 MFG0 REV2 REV1 REV0
Bit 7 = 1 Bit 6 (R) Bit 5 (R) Bit 4 (R) Bit 3 (R) Bit 2 (R) Bit 1 (R) Bit 0 (R)
Bit Field Definitions:
BIT FIELD DEFINITION DESCRIPTION
Bit 7 LED Panel Display panel using LED backlight, Bit 7 = 1
Bit [6:3] MFG[3:0] Manufacturer ID, see Table 5, default = 0
Bit [2:0] REV[2:0] Silicon rev (revs 0 to 7 allowed for silicon spins), default = 0
REGISTER 0x02 FAULT/STATUS REGISTER DEFAULT VALUE 0X00
Reserved Reserved 2_CH_SD 1_CH_SD BL_STAT OVCURR THRM_SHDN FAULT
Bit 7 (R) Bit 6 (R) Bit 5 (R) Bit 4 (R) Bit 3 (R) Bit 2 (R) Bit 1 (R) Bit 0 (R)
Bit Field Definitions:
BIT FIELD DEFINITION DESCRIPTION
Bit 5 2_CH_SD Two or more LED output channels are shut down (1 = shutdown, 0 = okay)
Bit 4 1_CH_SD One LED output channel is shut down (1 = shutdown, 0 = okay)
Bit 3 BL_STAT Backlight status (1 = BL on, 0 = BL off)
Bit 2 OV_CURR Input overcurrent (1 = overcurrent condition, 0 = current okay)
Bit 1 THRM_SHDN Thermal shutdown (1 = thermal fault, 0 = thermal okay)
Bit 0 FAULT Fault occurred (logic OR of all the fault conditions)
www.maximintegrated.com Maxim Integrated
│
20
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Thermal Shutdown
The MAX17105 includes a thermal-protection circuit.
When the local IC temperature exceeds +150°C (typ),
the controller and current sources shut down and do not
restart until the next enable signal is sent.
Design Procedure
All MAX17105 designs should be prototyped and tested
prior to production.
External component value choice is primarily dictated
by the output voltage and the maximum load current, as
well as maximum and minimum input voltages. Begin by
selecting an inductor value. Once the inductor is known,
choose the diode and capacitors.
Step-Up Converter Current Calculation
To ensure stable operation, the MAX17105 includes
slope compensation, which sets the minimum induc-
tor value. In continuous-conduction mode (CCM), the
minimum inductor value is calculated with the following
equation:
( )
OUT(MAX) DIODE S(MIN) S
CCM(MIN) SW(MIN)
V V -2 V R
L2 25.5mV f
+
=
OO
OO
where 25.5mV is a scale factor from the slope com-
pensation, LCCM(MIN) is the minimum inductor value
for stable operation in CCM, and RS =13.7mW (typ) is
the equivalent sensing-scale factor from the controller’s
internal current-sense circuit.
The controller can also operate in discontinuous-con-
duction mode (DCM). In this mode, the inductor value
can be lower, but the peak inductor current is higher
than in CCM. In DCM, the maximum inductor value is
calculated with the following equation:
S(MIN)
DCM(MAX) OUT(MAX) DIODE
2
S(MIN)
SW(MAX) OUT(MAX) OUT(MAX)
V
L 1- VV
V
2f V I
=
+
OE
OOO O
where LDCM(MAX) is the maximum inductor value for
DCM, η is the nominal regulator efficiency (85%), and
IOUT(MAX) is the maximum output current.
The output current capability of the step-up regulator is a
function of current limit, input voltage, operating frequen-
cy, and inductor value. Because the slope compensation
is used to stabilize the feedback loop, the inductor current
limit depends on the duty cycle, and is determined with
the following equation:
( )
LIM
S
25.5mV 0.75 - D
I 2A R
= + O
where 25.5mV is the scale factor from the slope compen-
sation, 2A is the current limit specified at 75% duty cycle,
and D is the duty cycle.
The output current capability depends on the current- limit
value and operating mode. The maximum output current
in CCM is governed by the following equation:
SS
OUT_CCM(MAX) LIM SW OUT
0.5 D V V
I I-
fLV
=
OO O OE
O
where ILIM is the current limit calculated above, η is the
nominal regulator efficiency (85%), and D is the duty
cycle. The corresponding duty cycle for this current is:
OUT S DIODE
OUT LIM ON DIODE
V -V V
DV -I R V
+
=+O
where VDIODE is the forward voltage of the rectifier diode
and RON is the internal MOSFET’s on-resistance (0.15W
(typ)).
The maximum output current in DCM is governed by the
following equation:
( )
( )
2
LIM SW OUT DIODE
OUT_DCM(MAX)
OUT OUT DIODE S
LI f V V
I
2 V V V -V
+
=+
O O OEO
OO
Inductor Selection
The inductance, peak current rating, series resistance,
and physical size should all be considered when select-
ing an inductor. These factors affect the converter’s oper-
ating mode, efficiency, maximum output load capability,
transient-response time, output voltage ripple, and cost.
www.maximintegrated.com Maxim Integrated
│
21
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
The maximum output current, input voltage, output volt-
age, and switching frequency determine the inductor
value. Very high inductance minimizes the current ripple,
and therefore reduces the peak current, which decreases
core losses in the inductor and I2R losses in the entire
power path. However, large inductor values also require
more energy storage and more turns of wire, which
increases physical size and I2R copper losses. Low
inductor values decrease the physical size but increase
the current ripple and peak current. Finding the best
inductor involves the compromises among circuit effi-
ciency, inductor size, and cost.
In choosing an inductor, the first step is to determine the
operating mode: continuous-conduction mode (CCM) or
discontinuous-conduction mode (DCM). The MAX17105
has a fixed internal slope compensation, which requires
minimum inductor value. When CCM mode is chosen,
the ripple current and the peak current of the inductor
can be minimized. If a small-size inductor is required,
DCM mode can be chosen. In DCM mode, the inductor
value and size can be minimized, but the inductor ripple
current and peak current are higher than those in CCM.
The controller can be stable, independent of the internal
slope-compensation mode, but there is a maximum induc-
tor value requirement to ensure the DCM operating mode.
The equations used here include a constant LIR, which
is the ratio of the inductor peak-to-peak ripple current to
the average DC inductor current at the full load current.
The controller operates in DCM mode when LIR is higher
than 2.0, and it works in CCM mode when LIR is lower
than 2.0. The best trade-off between inductor size and
converter efficiency for step-up regulators generally has
an LIR between 0.3 and 0.5. However, depending on the
AC characteristics of the inductor core material and ratio
of inductor resistance to other power path resistances, the
best LIR can shift up or down. If the inductor resistance
is relatively high, more ripples can be accepted to reduce
the number of required turns and increase the wire diam-
eter. If the inductor resistance is relatively low, increasing
inductance to lower the peak current can reduce losses
throughout the power path. If extremely thin high-resis-
tance inductors are used, as is common for LCD panel
applications, LIR higher than 2.0 can be chosen for DCM
operating mode.
Once a physical inductor is chosen, higher and lower
values of the inductor should be evaluated for efficiency
improvements in typical operating regions. The detail
design procedure for CCM can be described as:
Calculate the approximate inductor value using the
typical input voltage (VS), the maximum output cur-
rent (IOUT(MAX)), the expected efficiency (ηTYP) taken
from an appropriate curve in the Typical Operating
Characteristics, and an estimate of LIR based on the
above discussion:
2
S(MIN) OUT S(MIN) TYP
OUT OUT(MAX) SW
V V -V
LV I f LIR
=
E
O
The MAX17105 has a minimum inductor value limitation
for stable operation in CCM mode at low input voltage,
because of the internal fixed slope compensation. The
minimum inductor value for stability is calculated with the
following equation:
( )
OUT(MAX) DIODE S(MIN) S
CCM(MIN) SW(MIN)
V V -2 V R
L2 25.5mV f
+
=
OO
OO
where 25.5mV is a scale factor from slope compensa-
tion, and RS is the equivalent current-sensing scale fac-
tor (13.7mW typ).
Choose an available inductor value from an appropriate
inductor family. Calculate the maximum DC input current
at the minimum input voltage VS(MIN), using conserva-
tion of energy and the expected efficiency at that operat-
ing point (ηMIN) taken from an appropriate curve in the
Typical Operating Characteristics:
OUT(MAX) OUT
IN(DC,MAX) S(MIN) MIN
IV
IV
=O
OE
Calculate the ripple current at that operating point and the
peak current required for the inductor:
( )
S(MIN) OUT(MAX) S(MIN)
RIPPLE OUT(MAX) SW
V V -V
ILV f
=O
OO
RIPPLE
PEAK IN(DC,MAX)
I
II
2
= +
When the DCM operating mode is chosen to minimize the
inductor value, the calculations are different from those
above in CCM mode. The maximum inductor value for
DCM mode is calculated with the following equation:
S(MIN)
DCM(MAX) OUT(MAX) DIODE
2
S(MIN)
SW(MAX) OUT(MAX) OUT(MAX)
V
L 1- VV
V
2f V I
=
+
OE
OOO O
www.maximintegrated.com Maxim Integrated
│
22
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
The peak inductor current in DCM is calculated with the
following equation:
( )
( )
OUT(MAX) OUT(MAX) OUT(MAX) DIODE S(MIN)
PEAK
SW(MIN) OUT(MAX) DIODE
I 2 V V V -V
ILf V V
+
=+
OO O
O OEO
The inductor’s saturation current rating should exceed
IPEAK, and the inductor’s DC current rating should
exceed IIN(DC,MAX). For good efficiency, choose an
inductor with less than 0.1W series resistance.
Considering the circuit with eight 10-LED strings and
20mA LED full-scale current, the maximum load current
(IOUT(MAX)) is 160mA with a 32V output and a minimal
input voltage of 7V.
Choosing a CCM operating mode with LIR = 0.7 at 1MHz
and an estimating efficiency of 85% at this operating
point:
2
7V 32V - 7V 0.85
L 9.08µH
32V 160mA 1MHz 0.7
= =
×
In CCM, the inductor has to be higher than LCCM(MIN):
( )
CCM(MIN)
32V 0.4V - 2 7V 13.7m
L 5.5µH
2 25.5mV 0.9MHz
+
= =
OO I
OO
10µH inductor is chosen, which is higher the minimum L
that guarantees stability in CCM.
The peak inductor current at minimum input voltage is
calculated as follows:
( )
PEAK
7V 32V - 7V
160mA 32V
I 1.16A
7V 0.85 2 10µH 32V 0.9MHz
=+=
O
O
O O OO
Alternatively, choosing a DCM operating mode will lower
inductance and estimate efficiency of 85% at this oper-
ating point. Since DCM will have higher peak inductor
current at lower input, it will cause current limit when the
parameters are not chosen properly. Consider the case
with six 10-LED strings and 20mA LED full-scale current
to prevent excessive switch current from causing current
limit:
DCM(MAX)
2
7V
L 1- 32V 0.4V
(7V) 0.85 3.9µH
2 1.1MHz 32V 120mA
=
+
=
O
OO OO
3.3µH inductor is chosen. The peak inductor current at
minimum input voltage is calculated as follows:
( )
( )
PEAK
120mA 2 32V 32V 0.4V - 7V
I 1.40A
3.3µH 1.1MHz 0.85 32V 0.4V
+
= =
+
OO O
O OO
Output Capacitor Selection
The total output voltage ripple has two components: the
capacitive ripple caused by the charging and discharging
on the output capacitor, and the ohmic ripple due to the
capacitor’s equivalent series resistance (ESR):
RIPPLE RIPPLE(C) RIPPLE(ESR)
VV V= +
OUT(MAX) OUT(MAX) S(MIN)
RIPPLE(C) OUT OUT(MAX) SW
I V -V
V
CV f
≈
O
and:
RIPPLE(ESR) PEAK ESR(COUT)
V IR≈
where IPEAK is the peak inductor current (see the Inductor
Selection section).
The output voltage ripple should be low enough for the
FB_ current source regulation. The ripple voltage should
be less than 200mVP-P. For ceramic capacitors, the out-
put voltage ripple is typically dominated by VRIPPLE(C).
The voltage rating and temperature characteristics of the
output capacitor must also be considered.
Rectier Diode Selection
The MAX17105’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended
for most applications because of their fast recovery time
and low forward voltage. The diode should be rated to
handle the output voltage and the peak switch current.
Make sure that the diode’s peak current rating is at least
IPEAK calculated in the Inductor Selection section and
that its breakdown voltage exceeds the output voltage.
Overvoltage-Protection Determination
The overvoltage-protection circuit should ensure the
circuit safe operation; therefore, the controller should
limit the output voltage within the ratings of all MOSFET,
diode, and output capacitor components, while provid-
ing sufficient output voltage for LED current regulation.
The OVP pin is connected to the center tap of a resistive
voltage-divider (R1 and R2 in Figure 1) from the high-
voltage output. When the controller detects the OVP pin
voltage reaching the threshold VOVP_TH, typically 1.25V,
overvoltage protection is activated. Hence, the step-up
converter output overvoltage protection point is:
www.maximintegrated.com Maxim Integrated
│
23
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
OUT(OVP) OVP_TH
R1
V V (1 )
R2
= +O
In Figure 1, the output OVP voltage is set to:
OUT(OVP)
2.21M
V 1.25V (1 ) 39.89V
71.5k
= +=
I
OI
Input Capacitor Selection
The input capacitor (CIN) filters the current peaks drawn
from the input supply and reduces noise injection into
the IC. A 4.7µF ceramic capacitor is used in the typical
operating circuit (Figure 1) because of the high source
impedance seen in typical lab setups. Actual applications
usually have much lower source impedance since the
step-up regulator often runs directly from the output of
another regulated supply. In some applications, CIN can
be reduced below the values used in the typical operating
circuit. Ensure a low noise supply at IN by using adequate
CIN. Alternatively, greater voltage variation can be toler-
ated on CIN if IN is decoupled from CIN using an RC
lowpass filter.
LED Selection and Bias
The series/parallel configuration of the LED load and the
full-scale bias current have a significant effect on regula-
tor performance. LED characteristics vary significantly
from manufacturer to manufacturer. Consult the respec-
tive LED data sheets to determine the range of output
voltages for a given brightness and LED current. In
general, brightness increases as a function of bias cur-
rent. This suggests that the number of LEDs could be
decreased if higher bias current is chosen; however, high
current increases LED temperature and reduces operat-
ing life. Improvements in LED technology are resulting in
devices with lower forward voltage while increasing the
bias current and light output.
LED manufacturers specify LED color at a given LED cur-
rent. With lower LED current, the color of the emitted light
tends to shift toward the blue range of the spectrum. A
blue bias is often acceptable for business applications but
not for high-image-quality applications such as DVD play-
ers. Direct-PWM dimming is a viable solution for reducing
power dissipation while maintaining LED color integrity.
Careful attention should be paid to switching noise to
avoid other display quality problems.
Using fewer LEDs in a string improves step-up converter
efficiency, and lowers breakdown voltage requirements
of the external MOSFET and diode. The minimum num-
ber of LEDs in series should always be greater than the
maximum input voltage. If the diode voltage drop is lower
than maximum input voltage, the voltage drop across the
current-sense inputs (FB_) increases and causes excess
heating in the IC. Between 8 and 12 LEDs in series are
ideal for input voltages up to 20V.
Applications Information
LED VFB_ Variation
The forward voltage of each white LED may vary up
to 25% from part to part, and the accumulated voltage
difference in each string equates to additional power
loss within the IC. For the best efficiency, the voltage
difference between strings should be minimized. The
difference between lowest voltage string and highest
voltage string should be less than 8V (typ). Otherwise,
the internal LED short-protection circuit disables the high
FB string.
FB_ Pin Maximum Voltage
The current through each FB_ pin is controlled only
during the step-up converter’s on-time. During the con-
verter’s off-time, the current sources are turned off. The
output voltage does not discharge and stays high. The
MAX17105 disables the FB current source from which
the string is shorted. In this case, the step-up converter’s
output voltage is always applied to the disabled FB_ pin.
FB_ pin can withstand 45V.
PCB Layout Guidelines
Careful PCB layout is important for proper operation. Use
the following guidelines for good PCB layout:
1) Minimize the area of the high-current switching loop of
rectifier diode, internal MOSFET, and output capacitor
to avoid excessive switching noise.
2) Connect high-current input and output components
with short and wide connections. The high-current
input loop goes from the positive terminal of the input
capacitor to the inductor, to the internal MOSFET, then
to the input capacitor’s negative terminal. The high-
current output loop is from the positive terminal of the
input capacitor to the inductor, to the rectifier diode,
and to the positive terminal of the output capacitors,
reconnecting between the output capacitor and input
capacitor ground terminals. Avoid using vias in the
high-current paths. If vias are unavoidable, use mul-
tiple vias in parallel to reduce resistance and induc-
tance.
www.maximintegrated.com Maxim Integrated
│
24
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
3) Create a ground island (PGND) consisting of the
input and output capacitor ground and negative ter-
minal of the current-sense resistor. Connect all these
together with short, wide traces or a small ground
plane. Maximizing the width of the power ground
traces improves efficiency and reduces output volt-
age ripple and noise spikes. Create an analog ground
island (AGND) consisting of the overvoltage-detection
divider ground connection, the ISET and DFSET
resistor connections, the COMP resistor and capacitor
connections, and the device’s exposed backside pad.
Connect the AGND and PGND islands by connecting
the SGND pins directly to the exposed backside pad.
Make no other connections between these separate
ground planes.
4) Place the overvoltage-detection divider resistors as
close to the OVP pin as possible. The divider’s center
trace should be kept short. Placing the resistors far
away causes the sensing trace to become antennas
that can pick up switching noise. Avoid running the
sensing traces near LX.
5) Place the IN pin bypass capacitor as close to the
device as possible. The ground connection of the
IN bypass capacitor should be connected directly to
SGND pins with a wide trace.
6) Minimize the size of the LX node while keeping it wide
and short. Keep the LX node away from the feedback
node and ground. If possible, avoid running the LX
node from one side of the PCB to the other. Use DC
traces as a shield if necessary.
Refer to the MAX17105 evaluation kit for an example of
proper board layout.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN
NO.
24 TQFN-EP T2444+4 21-0139 90-0022
FB1
PGND
IN FAULT
LX
OVP
FB2
FB3
FB4
FB5
FB6
FB7
FB8
ISET
VCC
PWMI
PWM0
10kHz
MAX17105
DFSET
EN
SCL
SDA
OSC
COMP
EP
SGND
www.maximintegrated.com Maxim Integrated
│
25
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Chip Information
PROCESS: BiCMOS
Simplied Operating Circuit
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 5/09 Initial release —
1 12/09 Updated Electrical Characteristics, Typical Operating Characteristics graphs 1
and 2, and COMP pin function with specifications for final production version 2–7, 11
2 9/14 Removed automotive reference from Applications 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc. © 2014 Maxim Integrated Products, Inc.
│
26
MAX17105 8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
