MAX17129 Datasheet, PDF (1/21 Pages) Maxim Integrated Products – Low-Cost, 6-String WLED Drivers with Quick-PWM Step-Up Converter

19-5676; Rev 1; 9/11
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Low-Cost, 6-String WLED Drivers with
Quick-PWM Step-Up Converter
General Description
The MAX17129/MAX17149 are high-efficiency drivers
for white LEDs. They are designed for small- to medium-
sized LCDs that employ an array of LEDs as the light
source. An internal switch step-up controller with Quick-
PWMK drives the LED array, which can be configured for
up to 6 strings in parallel and either 11 LEDs (MAX17129)
or 6 LEDs in series (MAX17149) per string. Each string
is terminated with a ballast that achieves Q2% current-
regulation accuracy, ensuring even LED brightness and
provides an adjustable 10mA to 45mA full-scale LED
current. The devices have a wide input voltage range of
6V to 26V. The MAX17129 integrates an LDO to simplify
applications that have a single high-voltage supply. The
devices also feature a low-input-voltage mode for appli-
cations that have a 3V to 5.5V supply voltage.
The devices support both PWM and hybrid dimming
mode. In PWM dimming mode, the external PWM signal
directly controls the brightness of LEDs. The dimming
frequency ranges from 100Hz to 25kHz with 400ns mini-
mum on-time. In hybrid dimming mode, the LED current
amplitude can be adjusted to 25% of full-scale LED cur-
rent to improve system efficiency when brightness is low.
The devices have multiple features to protect the con-
troller from fault conditions. Separate voltage-feedback
loops limit the output voltage to safe operation. The open
and short-LED detection shuts down the faulty string
while keeping other strings operating normally.
The devices feature cycle-by-cycle current limit on the
internal switch to provide consistent operation and soft-
start capability. If the devices are in current-limit condi-
tion, the step-up converter is latched off after an internal
timer expires. A thermal-shutdown circuit provides anoth-
er level of protection and prevents ICs from damage.
The ICs’ step-up controller features an internal 0.25I (typ),
48V (max) power MOSFET with lossless current sense and
accurate cycle-by-cycle current limit. The Quick-PWM con-
trol architecture provides fast load-transient response with-
out requiring an external loop compensation component,
simplifies the external circuitry, and saves board area. The
Quick-PWM control scheme has constant off-time and
adjustable pseudo-fixed frequency, which enables a wide
variety of applications that can trade off component size
for operating frequency. Low feedback voltage at each
LED string (275mV typ at 20mA LED current) helps reduce
power loss and improve efficiency.
The ICs are available in a 16-pin, thin QFN package with
0.5mm lead spacing. The package is 3mm x 3mm with a
maximum thickness of 0.8mm for ultra-thin LCD panel design.
Features
S 3V to 26V Input Supply Voltage
S Up to Six Parallel Strings of Multiple Series-
Connected LEDs
S Step-Up Regulator with Quick-PWM Control Scheme
S Two-Level Selectable Switching Frequency
S 0.25I Internal HV Power MOSFET (48V max)
S Low String Feedback Voltage: 275mV at 20mA
LED Current
S Full-Scale LED Current Adjustable from 10mA to
45mA
S ±2% Current Regulation Accuracy Between Strings
S Support PWM and Hybrid Dimming Mode
S 100:1 Dimming Ratio
S 100Hz to 25kHz Dimming Frequency for PWM
Dimming Mode
S Open and Short LED Protection
S Output Overvoltage Protection
S Small 16-Pin, 3mm x 3mm Thin QFN Package
Applications
Notebook, Subnotebook, and Tablet Computer
Displays
Automotive Systems
Handy Terminals
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX17129ETE +
-40°C to +85°C ^{16 Thin QFN-EP*}
MAX17149ETE+
-40°C to +85°C ^{16 Thin QFN-EP*}
+Denotes lead(Pb)-free/RoHS-compatible package.
*EP = Exposed pad.
Simplified Operating Circuit appears at end of data sheet.
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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.