www.austriamicrosystems.com/LED-Driver-ICs

Revision 1.00

7 - 24

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 (see page 14).

Figure 8. AS1123 - Block Diagram

AS1123

REXT

OEN

CLK

SDI

LD

Current

Generators

Detailed

Error

Detection

16-Bit Data

Register

16-Bit Shift

Register

Temperature

Detection

16-Bit Open

Detection &

Error Register

16-Bit Short

Detection &

Error Register

Global

Error

Detection

SDO

Indicates 16 Bit

Control Logic