A6278
and
A6279
Serial-Input Constant-Current Latched
LED Drivers with Open LED Detection
Features and Benefits
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3.0 to 5.5 V logic supply range
Schmitt trigger inputs for improved noise immunity
Power-On Reset (POR)
Up to 90 mA constant-current sinking outputs
LED open circuit detection
Low-power CMOS logic and latches
High data input rate
20 ns typical staggering delay on the outputs
Internal UVLO and thermal shutdown (TSD) circuitry
Description
The A6278 and A6279 devices are specifically designed for
LED display applications. Each of these BiCMOS devices
includes a CMOS shift register, accompanying data latches,
and NPN constant-current sink drivers. The A6278 contains
8 sink drivers, while there are 16 in the A6279.
The CMOS shift register and latches allow direct interfacing
with microprocessor-based systems. With a 3.3 or 5 V logic
supply, typical serial data-input rates can reach up to 25 MHz.
The LED drive current is determined by the user’s selection of
a single resistor. A CMOS serial data output permits cascading
between multiple devices in applications requiring additional
drive lines. Open LED connections can be detected and signaled
back to the host microprocessor through the SERIAL DATA
OUT pin.
Four package styles are provided: an MLP/QFN surface mount,
0.90 mm overall height nominal (A6279 only); a DIP (type A)
for through-hole applications; and for leaded surface-mount, an
SOIC (type LW) and a TSSOP with exposed thermal pad (type
LP). All package styles for the A6278 are electrically identical
to each other, as are the A6279 package styles. All packages
are lead (Pb) free, with 100% matte tin plated leadframes.
Packages:
28 pin MLP/QFN (suffix ET)
16 and 24 pin DIP (suffix A)
16 and 24 pin TSSOP (suffix LP)
16 and 24 pin SOIC (suffix LW)
Not to scale
Functional Block Diagram
LOGIC
SUPPLY
SERIAL
DATA IN
CLOCK
V
DD
Serial - Parallel Shift Register
SERIAL
DATA OUT
V
DD
UVLO
OUTPUT
ENABLE
LATCH
ENABLE
Control Logic
Block
Latches
Output Control Drivers and Open Circuit Detector
REXT
I
O
Regulator
Exposed Pad
(ET and LP packages)
OUT7 (A6278)
OUT15 (A6279)
GND
OUT0 OUT1
V
LED
6278-DS, Rev. 4
ALLEGRO [ ALLEGRO MICROSYSTEMS ]
