34845 Datasheet, PDF (1/21 Pages) Freescale Semiconductor, Inc – Low Cost 6 Channel LED Backlight Driver with Integrated Power Supply

Freescale Semiconductor
Advance Information
Document Number: MC34845
Rev. 2.0, 9/2009
Low Cost 6 Channel LED
Backlight Driver with Integrated
Power Supply
34845
34845A/B
LED DRIVER
The 34845 series represents high efficiency LED drivers for use in
backlighting LCD displays from 10” to 17”+. Operating from supplies of
5.0 V to 21 V, the 34845 series is capable of driving up to 16 LEDs in
series in 6 separate strings. The LED current tolerance in the 6 strings
is within ±2% maximum and is set using a resistor to GND.
PWM dimming is performed by applying a PWM input signal to the
PWM pin which modulates the LED channels directly. An Enable Pin
(EN) provides for low power standby. Alternatively, a single wire
scheme selects power down when PWM is connected to the Wake Pin
and held low.
The integrated boost converter uses dynamic headroom control to
automatically set the output voltage. There are three device versions for
boost frequency; 34845 is 600 kHz, 34845A is 1.2 MHz and the 34845B
is 300 kHz. External compensation allows the use of different inductor/
capacitor combinations.
The 34845 includes fault protection modes for LED short and open,
over temperature, over current and over voltage errors. It features an
internally fixed OVP value of 60 V (typical) which protects the device in
the event of a failure in the externally programmed OVP. The OVP level
can be set by using an external resistor divider.
Features
• Input voltage of 5.0 to 21 V
• Boost output voltage up to 60 V
• 2.0 A integrated boost FET
• Fixed boost frequency - 300 kHz, 600 kHz or 1.2 MHz
• OTP, OCP, UVLO fault detection
• LED short/open protection
• Programmable LED current between 3.0 mA and 30 mA
• 24-Ld 4x4x0.65 mm μQFN Package
98ASA00087D
24-PIN QFN-EP
ORDERING INFORMATION
Device
Temperature
Range (T_A)
Package
MC34845EP/R2
MC34845AEP/R2
MC34845BEP/R2
-40° to 85°C
24 QFN-EP
Tape and Reel depicted with “R2”
Typical Applications
• PC Notebooks
• Netbooks
• Picture Frames
• Portable DVD Players
• Small Screen Televisions
• Industrial Displays
• Medical Displays
12V
CONTROL
UNIT
VIN
VDC1
VDC2
34845
SWA
SWB
VOUT
PGNDB
COMP
PGNDA
OVP
5V
EN
PWM
WAKE
ISET
GND EP
FAIL
CH1
CH2
CH3
CH4
CH5
CH6
GND
Figure 1. 34845 Simplified Application Diagram
* 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.
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