LM3528 Datasheet, PDF (1/32 Pages) National Semiconductor (TI) – High Efficiency, Multi Display LED Driver with 128 Exponential Dimming Steps and Integrated OLED Power Supply in a 1.2mm × 1.6mm μSMD Package

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
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.
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.
Output over-voltage protection shuts down the device if
V_OUT 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.
Features
■ ^{128 Exponential Dimming Steps}
■ ^{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}
■ ^{Programmable Pattern Generator Output for LED}
Indicator Function
■ ^{Drives up to 12 LED’s at 20mA}
■ ^{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}
■ ^{1.25MHz Fixed Frequency Operation}
■ ^{Dedicated Programmable General Purpose I/O}
■ ^{Active Low Hardware Reset}
Applications
■ ^{Dual Display LCD Backlighting for Portable Applications}
■ ^{Large Format LCD Backlighting}
■ ^{OLED Panel Power Supply}
■ ^{Display Backlighting with Indicator Light}
Typical Application Circuit
© 2008 National Semiconductor Corporation 300205
30020501
Typical PCB Layout
30020563
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