Gesture and proximity sensing ICs enable next-gen automotive HMI

March 14, 2013 // By Christoph Hammerschmidt
Touchscreen and voice control were yesterday. The next big thing in user interfaces - in the car as well as in other application fields - is proximity detection and gesture control. Belgian chipmaker Melexis has designed a family of ICs that enable design engineers to implement innovative human-machine interfaces that utilize these approaches.

Automotive Human-Machine Interfaces (HMIs) need to be intuitive and safe to use, On the other hand, new car buyers expect functions and features like smartphone and media integration. Optical proximity and gesture detection enable a more intuitive HMI experience. Typical challenges for such systems are cost, sunlight robustness, electro-magnetic interference and mechanical integration constraints, while supporting multiple OEM configurations. The MLX75030 and MLX75031 Optical Gesture and Proximity Sensing ICs address these challenges with Melexis' proprietary integrated ambient light suppression, proven electro-magnetic compliance, a small footprint and flexible system architecture.

The MLX75030 and MLX75031 feature two simultaneously operating light measurement channels which can detect the active optical reflection from a target. The proprietary integrated, ambient light suppression makes these channels highly tolerant to background light interference. Two additional channels are available to measure ambient light.

On system level, the MLX75030 and MLX75031 should be complemented by one or two LEDs and photodiodes, of any type, for active light detection. The MLX75030 allows external switches to drive the LEDs up to 1 A peak current, while the MLX75031 integrates the LED drivers to minimize external component count. Ambient light can be detected with up to two independent photodiodes. Any amount of detection channels can be added through multiplexing. Internal control logic, configurable user registers and SPI communication enable intuitive, programmable operation. Additional circuit functions like a watchdog timer, on-board temperature sensor and self-diagnostics are built-in to facilitate robust product design.

The digital output from the MLX75030 and MLX75031 ICs contain the measured active light and ambient light levels, which should be processed on the customer’s microcontroller to detect gestures such as swipe, zoom or scroll. A measurement rate of up to 700 Hz per measurement channel allows smooth interface response times.

The MLX75030 and MLX75031 ICs are offered in a compact (4 mm x 4 mm), 24-pin surface mount QFN package. Both devices have been AEC-Q100 qualified for - 40°C to 105°C