ISELED – The LED goes Digital: Page 3 of 5

October 25, 2017 // By Robert Kraus, Inova Semiconductors
ISELED – The LED goes Digital
At last November's electronica International Trade Fair in Munich, the ISELED Alliance unveiled a game-changing “digital LED” that delivers consistent colors and brightness without complex binning or recalibration. This entirely new concept utilizes a tiny controller chip embedded in the LED package to control and address three RGB LEDs; for the first time enabling highly sophisticated lighting effects with several hundred LEDs – a technological advance that is by no means limited to just in-car lighting.

Against this background, in the fall of 2015, Inova Semiconductor joined forces with BMW and started investigating alternative LED lighting solutions. The core concept behind the new "digital LED" is to do away with the present overly complex and expensive external processing which is required for delivering consistent brightness and color parameters, by embedding these process in the RGB LED itself. This essentially "digitalizes" the LED, which can now be addressed via a “lean” protocol – just like any other digital component – by simply defining the target parameters for color and brightness.

The centerpiece of this new digital LED is a tiny 1 mm² controller chip from Inova Semiconductors, which together with three LEDs – a red, a green and a blue one – is embedded by Malaysia-based Dominant Opto Technologies in a compact housing measuring only 3 x 4 x 0.6 mm. The controller chip provides the required driver stages for addressing the LEDs, and also includes all the devices required for calibrating all three individual LEDs precisely to the color and brightness reference values during the final test of the LED module at Dominant. And all this without the need for the usual binning and barcoding of the LEDs. The characteristics are stored in the controller chip's memory and subsequently used as corrective values when addressing the LEDs. In addition, a temperature sensor is integrated and calibrated during chip testing, which determines the current temperature of the LEDs and adjusts their brightness accordingly.   


The ISELED concept (bottom) compared with conventional solutions (top)
for addressing large numbers of RGB LEDs.

This eliminates the substantial “data overhead” of all LED characteristics communicated in today’s solutions between the system controller and the LEDs. The only remaining task of the communications protocol is thus to transmit the actual light control commands, all in a differential and highly EMC friendly manner, at a speed of only 2 Mbit/s via an unshielded two-wire line woven into the vehicle's cable harness.

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