AS1123
Datasheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1123 is designed to drive up to 16 LEDs through a fast serial interface and 16 constant-current output drivers. Furthermore, the AS1123
provides diagnostics for detecting open- or shorted-LEDs, as well as over-temperature conditions for LED display systems, especially LED traffic
sign applications.
The AS1123 contains an 16-bit shift register and an 16-bit data register, which convert serial input data into parallel output format. At AS1123 out-
put stages, sixteen regulated current sinks are designed to provide uniform and constant current with excellent matching between ports for driv-
ing LEDs within a wide range of forward voltage variations. External output current is adjustable from 0.5 to 40mA using an external resistor for
flexibility in controlling the brightness intensity of LEDs. The AS1123 guarantees to endure 5.5V maximum at the outputs.
The serial interface is capable of operating at a minimum of 30 MHz, satisfying the requirements of high-volume data transmission.
Using a multiplexed input/output technique, the AS1123 adds additional functionality to pins SDO, LD and OEN. These pins provide highly useful
functions (open- and shorted-LED detection, over-temperature detection), thus reducing pin count. Over-temperature detection will work on-the-
run, whereas the open- and shorted-LED detection can be used on-the-run or in low-current diagnostic mode
Figure 8. AS1123 - Block Diagram
+V
LED
REXT
OEN
LD
CLK
SDI
hn
ic a
al m
co s
A
nt G
en
ts
til
OUTN10
OUTN12
OUTN13
OUTN14
Temperature
Detection
16-Bit Open
Detection &
Error Register
16-Bit Short
Detection &
Error Register
AS1123
Current
Generators
16-Bit Data
Register
Detailed
Error
Detection
16-Bit Shift
Register
Control Logic
OUTN15
OUTN11
OUTN0
OUTN1
OUTN2
OUTN3
OUTN4
OUTN5
OUTN6
OUTN7
OUTN8
OUTN9
Te
c
Indicates 16 Bit
Revision 1.00
lv
Global
Error
Detection
al
SDO
id
7 - 24
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