Rainbow Electronics MAX17127 - Manual

_______________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
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MAX17127
Six-String WLED Driver with Integrated
Step-Up Converter
General Description
The MAX17127 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
converter drives the LED array, which can be configured
for up to six strings in parallel and 13 LEDs per string.
Each string is terminated with ballast that achieves Q2%
current-regulation accuracy, ensuring even LED bright-
ness. The MAX17127 has a wide input voltage range
from 5V to 26V, and provides adjustable 10mA to 30mA
full-scale LED current.
The MAX17127 can implement brightness control through
the PWM signal input, and LED current is directly con-
trolled by the external dimming signal’s frequency and
duty cycle.
The MAX17127 has multiple features to protect the con-
troller from fault conditions. Once an open/short string is
detected, the fault string is disabled while other strings
can still operate normally. The controller features cycle-
by-cycle current limit to provide constant operation and
soft-start capability. If the MAX17127 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. When thermal shut-
down happens, the MAX17127 is latched off.
The MAX17127’s step-up controller features an inter-
nal 0.12I (typ), 48V (max) power MOSFET with local
current-sense amplifier for accurate cycle-by-cycle cur-
rent limit. This architecture greatly simplifies the external
circuitry and saves PCB space. Low-feedback volt-
age at each LED string helps reduce power loss and
improve efficiency. The MAX17127 features resistor-
adjustable switching frequency from 250kHz to 1MHz,
which enables a wide variety of applications that can
trade off component size for operating frequency.
The MAX17127 is available in a thermally enhanced,
lead-free, 20-pin, 4mm x 4mm thin QFN package.
Features
S
5V to 26V Input Supply Voltage
S
Up to Six Parallel Strings Multiple Series-
Connected LEDs
S
250kHz to 1MHz Adjustable Switching Frequency
S
0.12I Internal HV Power MOSFET (48V max)
S
Low String Feedback Voltage: 480mV at 20mA
LED Current
S
Full-Scale LED Current Adjustable from 10mA to
30mA
S Q 2% Current-Regulation Accuracy Between
Strings
S
400ns Minimum String On-Time
S
100Hz to 25kHz PWM Input Range
S
Open and Short LED Protection
S
Output Overvoltage Protection
S
Thermal Shutdown
S
Small 20-Pin, 4mm x 4mm Thin QFN Package
Applications
Notebook, Subnotebook, and Tablet Computer
Displays
Automotive Systems
Handy Terminals
19-5164; Rev 0; 3/10
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Simplified Operating Circuit appears at end of data sheet.
Ordering Information
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
MAX17127ETP+ -40°C to +85°C 20 TQFN-EP*