34844_09 Datasheet, PDF (1/37 Pages) Freescale Semiconductor, Inc – 10 Channel LED Backlight Driver with Integrated Power Supply

Freescale Semiconductor
Advance Information
Document Number: MC34844
Rev. 5.0, 5/2009
10 Channel LED Backlight Driver
with Integrated Power Supply
34844
The 34844 is a 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 I²C/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 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 600 kHz, but may be programmed via
I²C 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 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.
LED DRIVER
EP SUFFIX (PB-FREE)
98ASA10800D
32-PIN QFN-EP
ORDERING INFORMATION
Features
• Input voltage of 7.0 to 28 V
• Boost output voltage up to 60 V, with Dynamic
Headroom Control (DHC)
• 3.0 A integrated boost FET
• Up to 50 mA 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
100 to 25,000Hz
• 32-Ld 5x5x1.0 mm TQFN Package
• Pb-free packaging designated by suffix code EP
Device
MC34844EP/R2
Temperature
Range (T_A)
-40°C to 105°C
Applications
• Monitors - up to 27 inch
• Personal Computer Notebooks
• GPS Screens
• Small screen Televisions
Package
32 QFN-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 new product.
Specifications and information herein are subject to change without notice.
© Freescale Semiconductor, Inc., 2009. All rights reserved.