AS1123 ‘Green’ LED Driver
Oct 2011ams AGRequest Info
UNTERPREMSTAETTEN, Austria, Oct. 25, 2011 — The AS1123, manufactured by austriamicrosystems, is a constant-current, 16-channel “green” LED driver with an on-chip diagnostic read-back function. It is for use in industrial applications, indoor/outdoor public information displays, LED panels and large LED video walls.
Designed with a maximum LED supply voltage of 5.5 V, the power-efficient direct LED driver is optimized for panels where only a single LED is connected per output. The optimization of the driver to those low supply voltages allows for up to 50% lower VDS versus existing higher voltage output drivers. This reduction of VDS gives better efficiency resulting in lower power dissipation. The AS1123 LED driver also features integrated diagnostics for overtemperature, open-LED and shorted-LED conditions. Internal registers store global fault status information as well as the detailed temperature/open-LED, shorted-LED conditions for future analysis.
The driver features a low-current diagnostic mode to eliminate display flicker during global fault testing. A small test current is applied to the display for a short time. As a result, LED testing is not visible and can therefore be applied during normal operation. These features make the AS1123 well suited for fixed- or slow-rolling displays. Other applications include large LED matrix displays, displays in elevators, public transportation, and large displays in stadiums and public areas.
The output current is adjustable up to 40 mA per channel using an external resistor, and output current accuracy is ±3% between LEDs and between integrated circuits. This ensures high picture quality and uniform brightness for an LED display because it virtually eliminates intensity variations between LEDs and LED modules.
A full high-definition display uses 6 million LEDs, so it’s important that the LED driver be optimized for power because saving a few milliwatts per LED times 6 million yields power savings in kilowatts. This results in cost savings during operation and enables an eco-friendly design. Every saved kilowatt hour saves more than half a kilogram of CO2.
The driver is available in a 4 × 4-mm TQFN-24 and a QSOP-24 package. It operates from a 3- to 5.5-V supply over a temperature range of −40 to 85 ºC.