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Document Number: MC34844
Rev. 10.0, 8/2014
Freescale Semiconductor
Technical Data
© Freescale Semiconductor, Inc., 2009-2014. All rights reserved.
10 Channel LED Backlight Driver
with Integrated Power Supply
The 34844 is a SMARTMOS high efficiency, LED driver for use in
backlighting LCD displays from 10" to 20"+. Operating from supplies of 7.0 to
28
V, the MC34844 is capable of driving up to 160 LEDs in 10 parallel strings.
Current in the 10 strings is matched to within 2%, and can be programmed via
the I
2
C/SM Bus interface.
The 34844 also includes a Pulse Width Monitor (PWM) generator for LED
dimming. The LEDs can be dimmed to one of 256 levels, programmed through
the I
2
C/SM Bus interface. Up to 65,000:1 (256:1 PWM, 256:1 Current DAC)
dimming ratio.
The integrated boost converter generates the minimum output voltage
required to keep all LEDs illuminated with the selected current, providing the
highest efficiency possible.
The 34844 has an integrated boost self-clock at a default frequency of
600
kHz, but may be programmed via I
2
C to 150/300/600/1200 kHz. The PWM
frequency can be set from 100
Hz to 25 kHz, or can be synchronized to an
external input. If not synchronized to another source, the internal PWM rate
outputs on the CK pin. This enables multiple devices to be synchronized
together.
The 34844 has a default boost frequency of 320 kHz, but may be
programmed via I
2
C to 160/320/650/1300 kHz. The PWM frequency can be set
from 110
Hz to 27 kHz, or can be synchronized to an external input. If not
synchronized to another source, the internal PWM rate outputs on the CK pin.
This enables multiple devices to be synchronized together.
The 34844 also supports optical/temperature closed loop operation and
features LED overtemperature protection, LED short protection, and LED open
circuit protection. The IC includes overvoltage protection, overcurrent
protection, and undervoltage lockout.
Features
• Input voltage of 7.0 to 28 V
•2.5 A integrated boost FET
•Up to 80 mA on the 34844 LED current per channel
• 90% efficiency (DC:DC)
•I
2
C/SM Bus interface
• 10 channel current mirror with ±2.0% current matching
• Boost output voltage up to 60V, with Dynamic Headroom Control (DHC)
• PWM frequency programmable or synchronizable from 110 to 27,000 Hz
• 32-Ld 5x5x1.0 mm TQFN Package
LED DRIVER
34844
EP SUFFIX (PB-FREE)
98ASA10800D
32-PIN QFN-EP
Applications
• Monitors and HDTV - up to 42 inch
• Personal Computer Notebooks
• GPS Screens
• Small screen Televisions
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