Freescale Semiconductor
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Document Number: MC34844
Rev 2.0, 9/2008
10 Channel LED Backlight Driver
with Integrated Power Supply
The 34844 is a high efficiency, LED driver for use in backlighting
LCD displays from 10" to 20"+. Operating from supplies of 7V to 28V,
the 34844 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 integrated boost self-
clocks at a default frequency of 600kHz, but may be programmed via
I
2
C to 150/300/600/1200 kHz. The PWM frequency can be set from
100Hz to 25kHz, 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 also features LED over-temperature protection, LED short
protection, and LED open circuit protection. The IC also includes over-
voltage protection, over-current protection, and under-voltage lockout.
Device
34844
LED DRIVER
EP SUFFIX (PB-FREE)
98ASA10800D
32-PIN QFN-EP
ORDERING INFORMATION
Temperature
Range (T
A
)
-40°C to 105°C
Package
32 QFN-EP
Features
•
•
•
•
•
•
•
•
Input voltage of 7.0 to 28V
Boost output voltage up to 60V, with auto V
OUT
selection.
3.0A integrated boost FET
Up to 50mA LED current per channel
90% efficiency (DC:DC)
10-channel current mirror with ±2% current matching
I
2
C/SM-Bus interface
PWM frequency programmable or synchronizable from
100Hz to 25,000Hz
• Pb-free packaging designated by suffix code EP
7.0 to 28V
PC34844EP/R2
Applications
•
•
•
•
Monitors - up to 27 inch
Personal Computer Notebooks
GPS Screens
Small screen Televisions
34844
VIN
VDC1
VDC2
VDC3
VOUT
PGNDA
PGNDB
FAIL
I0
I1
I2
I3
I4
I5
I6
I7
I8
I9
VCC
SWA
SWB
COMP
SLOPE
SCK
SDA
PWM
A0/SEN
CK
M/~S
EN
VDC1
ISET
PIN
NIN
GND
Control Unit
VDC1
~
~
~
~
~
~
~
~
~
~
VDC1
Figure 1. Simplified Application Diagram (SM-Bus Mode)
* This document contains certain information on a product under development. Freescale
reserves the right to change or discontinue this product without notice
© Freescale Semiconductor, Inc., 2008. All rights reserved.
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
