A6281EESTR-T Datasheet, PDF (1/11 Pages) Allegro MicroSystems – 3-Channel Constant Current LED Driver with Programmable PWM Control

A6281
3-Channel Constant Current LED Driver
with Programmable PWM Control
Features and Benefits
▪ 3 × 10-bit PWM brightness settings
▪ 3 × 7-bit dot correction current settings
▪ 5 to 17 V operation
▪ Wide output current range, 10 to 150 mA per channel
▪ Internally generated PWM clock
▪ Serial port operates at up to 5 MHz
▪ Data and clock logic architecture allows single
microcontroller control of large quantities of serially-
connected A6281s at fast data transfer rate
▪ Buffered logic outputs to drive cables
▪ Thermal shutdown and UVLO protection
▪ Power-On Reset
Package: 16-terminal QFN (suffix ES)
3 mm x 3 mm footprint
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
Continued on the next page…
Power Supply Bus
Clock
Data
Latch
Output Enable
Microprocessor
Control Board
Cat5 UTP
Application Diagram
VLED
VIN OutR OutG OutB
Clock In
Clock Out
Data In
Data Out
Latch In
Latch Out
OE In
OE Out
VREG A6281 ^REXT
Pixel Board #1
Cat5 UTP
VLED
VIN OutR OutG OutB
Clock In
Clock Out
Data In
Data Out
Latch In
Latch Out
OE In
OE Out
VREG A6281 ^REXT
Pixel Board #2
Cat5 UTP
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