MAX17061 Datasheet, PDF (1/26 Pages) Maxim Integrated Products – 8-String White LED Driver with SMBus for LCD Panel Applications

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.
Applications
Notebook, Subnotebook,
and Tablet Computer
Displays
Automotive Systems
Handy Terminals
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
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX17061ETI+ -40^oC to +85^oC 28 Thin QFN (4mm x 4mm)
+Denotes a lead-free package.
Simplified Operating Circuit
L1
D1
VOUT
VIN
VDD ^IN
VCC
LX1, 2
ISET
PGND1, 2
R1
CCV
OV
R2
MAX17061
PWM
PWMI
PWMO
FB1
GND
FB2
N.C. OSC
FB3
FB4
CLK
SCL
FB5
FB6
DATA
SDA
FB7
FSET
FB8
EP
Pin Configuration appears at end of data sheet.
SMBus is a trademark of Intel Corp.
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