A6278 Datasheet, PDF (1/18 Pages) Allegro MicroSystems – Serial-Input Constant-Current Latched LED Drivers with Open LED Detection

A6278 and A6279
Serial-Input Constant-Current Latched
LED Drivers with Open LED Detection
Features and Benefits
▪ 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
Packages:
16 and 24 pin DIP (suffix A)
16 and 24 pin TSSOP (suffix LP)
16 and 24 pin SOIC (suffix LW)
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.
Three package styles are provided: 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.
Not to scale
Functional Block Diagram
LOGIC
SUPPLY
SERIAL
DATA IN
VDD
CLOCK
VDD
OUTPUT
ENABLE
LATCH
ENABLE
Control Logic
Block
UVLO
Serial - Parallel Shift Register
Latches
SERIAL
DATA OUT
REXT
I_O
Regulator
Exposed Pad
(LP package)
Output Control Drivers and Open Circuit Detector
OUT0 OUT1
GND
OUT7 (A6278)
OUT15 (A6279)
V_LED
6278-DS, Rev. 2