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Description
The A6281 is a 3-channel constant current LED driver that
has a wide range of output currents. The A6281 controls LED
brightness with a Pulse Width Modulation (PWM) scheme
that gives the application the capability of displaying a billion
colors in an RGB cluster. The maximum current is set by an
external resistor.
The LED brightness is controlled by performing PWM control
on the outputs. The brightness data of the PWM signal for
each LED is stored in three 10-bit registers. The peak value
for each LED can be adjusted (dot-corrected) to compensate
for mismatch, aging, and temperature effects. All the internal
latched registers are loaded by a 32-bit shift register. One
address bit controls whether dot correction/clock divider ratio
or brightness data is loaded into the registers. The remaining
bits are used for the data.
The A6281 is designed to minimize the number of components
needed to drive LEDs with large pixel spacing. A large number
of A6281s can be daisy chained together and controlled by
just four control signals (clock, serial data, latch, and output
enable). Each of these inputs is buffered to drive the next chip
in the chain. Also, VIN can be tied to the LED voltage supply
Package: 16-terminal QFN (suffix ES)
3 mm x 3 mm footprint
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Application Diagram
Power Supply Bus
V
LED
V
LED
Clock
Data
Latch
Output Enable
Microprocessor
Cat5 UTP
V
IN
Out
R
Out
G
Out
B
Clock In
Clock Out
Data In
Data Out
Latch In
Latch Out
OE In
OE Out
V
REG
A6281 R
EXT
Cat5 UTP
V
IN
Out
R
Out
G
Out
B
Clock Out
Clock In
Data Out
Data In
Latch In
Latch Out
OE Out
OE In
V
REG
A6281 R
EXT
Cat5 UTP
Control Board
Pixel Board #1
Pixel Board #2
Pixel Board #N
Figure 1. Functional drawing of daisy chained display application. Additional pixel boards
with A6281 ICs can be applied.
A6281-DS, Rev. 1
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