MC34845BEPR2 Freescale Semiconductor, MC34845BEPR2 Datasheet - Page 9

• Manufacturer Part Number: MC34845BEPR2
• Description: IC LED DVR BACKLIGHT 6CH 24QFN
• Manufacturer: Freescale Semiconductor
• Type: Backlight, White LED, Color LEDr

Specifications of MC34845BEPR2

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: Yes
• Type - Primary: Backlight
• Frequency: 270kHz ~ 330kHz
• Voltage - Supply: 5 V ~ 21 V
• Voltage - Output: 8 V ~ 60 V
• Mounting Type: Surface Mount
• Package / Case: 24-QFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 30mA
• Internal Switch(s): Yes
• Efficiency: 90%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

displays for many years. This technology is now rapidly
replacing the incumbent Cold Cathode Fluorescent Lamp
(CCFL) in mid-size displays such as those used use in
notebooks, monitors and industrial/ consumer displays. LEDs
offer a number of advantages compared to the CCFL,
including lower power, thinner, longer lifetime, low voltage
drive, accurate wide-range dimming control and advanced
architectures for improved image quality. LEDs are also void
of hazardous materials such as mercury which is used in
CCFL.
size of the display and features required. For displays in the
10” to 17” + range such as those used in notebooks, edge-lit
backlights offer very thin designs down to 2mm or less. The
efficiency of the LED backlight also extends battery life in
POWER SUPPLY
internal regulators generate internal rails for internal
operation. Both rails are de-coupled using capacitors on the
VDC1 and VDC2 pins.
UVLO mechanisms. When any voltage is below the UVLO
threshold, the device stops operating. All UVLO comparators
have hysteresis to ensure constant on/off cycling does not
occur.
ENABLE and PWM signals is important since the 34845
device will behave differently depending on how the
sequence of these signals is applied. For the case where VIN
is applied before the ENABLE and PWM signals, the device
will have no limitation in terms of how fast the VIN ramp
should be. However for the case where the PWM and
ENABLE signals are applied before VIN, the ramp up time of
VIN between 0V and 5V should be no longer than 2ms.
Analog Integrated Circuit Device Data
Freescale Semiconductor
LED backlighting has been popular for use in small LCD
LED backlights use different architecture depending on the
The 34845 supports 5.0V to 21V at the VIN input pin. Two
The VIN, VDC1, and VDC2 supplies each have their own
The power up sequence for applying VIN respect to the
FUNCTIONAL DEVICE OPERATION
FUNCTIONAL DESCRIPTION
INTRODUCTION
portable equipment compared to CCFL. In large size panels,
direct backlights support advanced architectures such as
local dimming, in which power consumption and contrast ratio
are drastically improved. Edge lighting can also be used in
large displays when low cost is the driving factor.
17” + range with edge-lit backlights. The device supports LED
currents up to 30mA and supports up to 6 strings of LEDs.
This enables backlights up to 10W to be driven from a single
device. The device includes a boost converter to deliver the
required LED voltage from either a 2 or 3 cell Li-ion battery,
or a direct 12V input supply. The current drivers match the
current between devices to provide superior uniformity
across the display. The 34845 provides for a wide range of
PWM dimming from a direct PWM control input.
Figures 4 and 5 illustrate the two different power up
conditions.
The 34845 targets mid size panel applications in the 10” to
VOUT
PWM
Figure 4. Power up sequence case 1, VIN applied
VIN
EN
before the ENABLE and PWM signals.
No limitation for VIN ramp up time.
FUNCTIONAL DESCRIPTION
Boost
Soft Star t
INTRODUCTION
34845
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