19-4562; Rev 1; 12/09
EVAALVUAAILTAIOBNLEKIT
8-String WLED Driver with Integrated Step-Up
Regulator and SMBus/PWM Dimming Capability
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 Q2%
current regulation accuracy, ensuring even LED bright-
ness. 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 adjusted
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 technol-
ogy (DPST) to maximize battery life. The MAX17105 also
has direct PWM control mode, in which the PWMI directly
controls the LED current turn on/off and the SMBus inter-
face 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 over-
current-limit fault, thermal shutdown, or output-voltage
short condition 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.
Notebook, Subnotebook,
and Tablet Computer
Displays
Applications
Automotive Systems
Handy Terminals
Features
S 6V to 28V Input Supply Voltage
S Up to Eight Parallel-String Multiple Series
Connected LEDs
S 500kHz-to-2MHz Adjustable Switching Frequency
S 0.15I Internal HV Power MOSFET (45V max)
S Low-String Feedback Voltage: 500mV at 20mA
LED current
S Full-Scale LED Current Adjustable from 0mA to
30mA
S Q2% Current Regulation Accuracy Between Strings
S 100:1 Dimming Ratio at 25kHz Direct PWM
Frequency
S 100Hz to 30kHz PWMI Input Range for DPWM
Mode and 10kHz Q5% for SMBus Mode
S 100Hz to 5kHz Adjustable DPWM Frequency
S Full-Range Dimming with 8-Bit Resolution
S Open and Short LED Protection
S Output Overvoltage Protection
S Thermal Shutdown
S FAULT Output to Drive p-Channel MOSFET
S Small 24-Pin, 4mm x 4mm, Thin QFN Package
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX17105 ETG+ -40NC to +85NC
24 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configuration
TOP VIEW
18 17 16 15 14 13
LX 19
12 FB3
PWMI 20
11 FB2
EN 21
SCL 22
MAX17105
10 FB1
9 SGND
SDA 23
8 FAULT
DFSET 24
7 IN
12 3 4 56
THIN QFN
4mm x 4mm
SMBus is a trademark of Intel Corp.
Simplified Operating Circuit appears at end of data sheet.
________________________________________________________________ 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.
