© 2010 National Semiconductor Corporation
High-Efficiency LED Backlight Driver for Notebooks
General Description
The LP8550 is a white LED driver with integrated boost con-
verter. It has six adjustable current sinks which can be con-
trolled by PWM input or with I
The boost converter has adaptive output voltage control
based on the LED driver voltages. This feature minimizes the
power consumption by adjusting the voltage to lowest suffi-
cient level in all conditions.
LED outputs have 8-bit current resolution and up to 13-bit
PWM resolution with additional 1-3 bit dithering to achieve
smooth and precise brightness control. Proprietary Phase
Shift PWM control is used for LED outputs to reduce peak
current from the boost converter, thus making the boost ca-
pacitors smaller. The Phase Shifting scheme also eliminates
audible noise.
Internal EEPROM is used for storing the configuration data.
This makes it possible to have minimum external component
count and make the solution very small.
LP8550 has safety features which make it possible to detect
LED outputs with open or short fault. As well low input voltage
and boost over-current conditions are monitored and chip is
turned off in case of these events. Thermal de-rating function
prevents overheating of the device by reducing backlight
brightness when set temperature has been reached.
LP8550 is available in National's micro SMD-25 package.
NOTICE: This document is not a full datasheet. For more
information regarding this product or to order samples,
please contact your local National Semiconductor sales
office or visit http://www.national.com/support/dir.html.
Typical Application (1)
2
C-compatible serial interface.
LP8550 PRODUCT BRIEF
301163
Features
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Applications
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High-voltage DC/DC boost converter with integrated FET
with four switching frequency options: 156/312/625/1250
kHz
2.7V – 22V input voltage range to support 1x…5x cell Li-
Ion batteries
Programmable PWM resolution
-8 to 13 true bit (steady state)
-Additional 1 to 3 bits using dithering during brightness
changes
I
Automatic PWM & current dimming for improved efficiency
PWM output frequency and LED current set through
resistors
Optional synchronization to display V
6 LED outputs with LED fault (short/open) detection
Low input voltage, over-temperature, over-current
detection and shutdown
Minimum number of external components
Micro SMD-25 package, 2.466 x 2.466 x 0.6 mm
Notebook and Netbook LCD Display LED Backlight
LED Lighting
2
C and PWM brightness control
30116370
SYNC
September 2, 2010
signal
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