August 3, 2008
LM3528
High Efficiency, Multi Display LED Driver with 128
Exponential Dimming Steps and Integrated OLED Power
Supply in a 1.2mm × 1.6mm µSMD Package
General Description
Features
The LM3528 current mode boost converter offers two sepa-
rate outputs. The first output (MAIN) is a constant current sink
for driving series white LED’s. The second output (SUB/FB)
is configurable as a constant current sink for series white LED
bias, or as a feedback pin to set a constant output voltage for
powering OLED panels.
128 Exponential Dimming Steps
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Programmable Auto-Dimming Function
Up to 90% Efficient
Low Profile 12 Bump µ-SMD Package (1.2mm x 1.6mm x
0.6mm)
Integrated OLED Display Power Supply and LED Driver
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As a dual output white LED bias supply, the LM3528 adap-
tively regulates the supply voltage of the LED strings to max-
imize efficiency and insure the current sinks remain in
regulation. The maximum current per output is set via a single
external low power resistor. An I2C compatible interface al-
lows for independent adjustment of the LED current in either
output from 0 to max current in 128 exponential steps. When
configured as a white LED + OLED bias supply the LM3528
can independently and simultaneously drive a string of up to
6 white LED’s and deliver a constant output voltage of up to
21V for OLED panels.
Programmable Pattern Generator Output for LED
Indicator Function
Drives up to 12 LED’s at 20mA
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Drives up to 5 LED’s at 20mA and delivers 18V at 40mA
1% Accurate Current Matching Between Strings
Internal Soft-Start Limits Inrush Current
True Shutdown Isolation for LED’s
Wide 2.5V to 5.5V Input Voltage Range
22V Over-Voltage Protection
Output over-voltage protection shuts down the device if
VOUT rises above 22V allowing for the use of small sized low
voltage output capacitors. Other features include a dedicated
general purpose I/O (GPIO) and a multi-function pin (HWEN/
PGEN/GPIO) which can be configured as a 32 bit pattern
generator, a hardware enable input, or as a GPIO. When
configured as a pattern generator, an arbitrary pattern is pro-
grammed via the I2C compatible interface and output at
HWEN/PGEN/GPIO for indicator LED flashing or for external
logic control. The LM3528 is offered in a tiny 12-bump µSMD
package and operates over the -40°C to +85°C temperature
range.
1.25MHz Fixed Frequency Operation
Dedicated Programmable General Purpose I/O
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Active Low Hardware Reset
Applications
Dual Display LCD Backlighting for Portable Applications
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Large Format LCD Backlighting
OLED Panel Power Supply
Display Backlighting with Indicator Light
30020563
Typical PCB Layout
30020501
Typical Application Circuit
© 2008 National Semiconductor Corporation
300205
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