MC34844 Datasheet, PDF (1/37 Pages) Freescale Semiconductor, Inc – 10 Channel LED Backlight Driver with Integrated Power Supply

Freescale Semiconductor
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10 Channel LED Backlight Driver
with Integrated Power Supply
Document Number: MC34844
Rev 2.0, 9/2008
34844
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 I²C/SM-Bus interface.
LED DRIVER
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 I²C/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
I²C 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.
EP SUFFIX (PB-FREE)
98ASA10800D
32-PIN QFN-EP
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.
Features
ORDERING INFORMATION
Device
Temperature
Range (T_A)
Package
• Input voltage of 7.0 to 28V
PC34844EP/R2 -40°C to 105°C
32 QFN-EP
• Boost output voltage up to 60V, with auto V_OUT selection.
• 3.0A integrated boost FET
Applications
• Up to 50mA LED current per channel
• 90% efficiency (DC:DC)
• 10-channel current mirror with ±2% current matching
• I²C/SM-Bus interface
• PWM frequency programmable or synchronizable from
• Monitors - up to 27 inch
• Personal Computer Notebooks
• GPS Screens
• Small screen Televisions
100Hz to 25,000Hz
• Pb-free packaging designated by suffix code EP
7.0 to 28V
Control Unit
VDC1
VDC1
VDC1
VIN
VDC1
VDC2
VDC3
34844
SWA
SWB
VOUT
COMP
SLOPE
PGNDA
PGNDB
SCK
SDA
PWM
A0/SEN
CK
M/~S
EN
ISET
PIN
NIN
GND
FAIL
I0
I1
I2
I3
I4
I5
I6
I7
I8
I9
VCC
~~~~~~~~~~
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.