AS1109
Data Sheet - D e t a i l e d D e s c r i p t i o n
8 Detailed Description
The AS1109 is designed to drive up to 8 LEDs through a fast serial interface and 8 constant-current output drivers. Fur-
thermore, the AS1109 provides diagnostics for detecting open- or shorted-LEDs, as well as over-temperature condi-
tions for LED display systems, especially LED traffic sign applications.
The AS1109 contains an 8-bit shift register and an 8-bit data register, which convert serial input data into parallel output
format. At AS1109 output stages, eight regulated current sinks are designed to provide uniform and constant current
with excellent matching between ports for driving LEDs within a wide range of forward voltage variations. External out-
put current is adjustable from 0.5 to 100mA using an external resistor for flexibility in controlling the brightness intensity
of LEDs. The AS1109 guarantees to endure 15V 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 AS1109 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 9. Block Diagram
+V
LED
OUTN0
OUTN1
OUTN2
OUTN3
OUTN4
OUTN5
OUTN6
OUTN7
REXT
Current
Generators
OEN
LD
Temperature
Detection
8-Bit Open
Detection &
Error Register
8-Bit Short
Detection &
Error Register
AS1109
8-Bit Data
Register
Detailed
Error
Detection
Global
Error
Detection
CLK
SDI
8-Bit Shift
Register
Control Logic
SDO
Indicates 8 Bit Path
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