www.austriamicrosystems.com

Revision 1.18

8 - 26

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 (see page 15).

Figure 9. Block Diagram

AS1109

REXT

OEN

CLK

SDI

LD

Current

Generators

Detailed

Error

Detection

8-Bit Data

Register

8-Bit Shift

Register

Temperature

Detection

8-Bit Open

Detection &

Error Register

8-Bit Short

Detection &

Error Register

Global

Error

Detection

SDO

Indicates 8 Bit Path

Control Logic

OUTN0

OUTN1

OUTN2

OUTN3

OUTN4

OUTN5

OUTN6

OUTN7