Software-controlled magnetic sensing gives HMI-design flexibility

November 17, 2014 // By Graham Prophet
Calling it a software-defined sensor, Melexis has introduced a magnetic sensing product that it describes as ultra-flexible, and that gives engineers great freedom in defining HMI implementations through its breadth of programmable parameters.

Melexis is aiming this device beyond the automotive market to general sensing applications; it gives, the company says, three-axis sensing without a great deal of signal processing. You can access “raw” measurements from its SPI /I²C interface.

This fully programmable, extremely compact sensor IC capable of accurately measuring changes in magnetic flux density along its X, Y and Z axes. Based on the company's Triaxis technology, the MLX90393 provides “almost unlimited” scope with which all manner of human machine interface implementations can be accomplished - from joystick, slide switches, push/pull switches, levers, linear swipe switches and rotary knobs, right through to complex 3D position sensing systems. The company notes that rotary knobs, joysticks, and thumbwheels can all readily be given an added “push” detection axis. Suitable for micropower applications, the IC draws 2.5 µA of current when idle. It employs a monolithic pixel cell arrangement and has a 16-bit resolution output.

Using its SPI and I²C interfaces, engineers can access the MLX90393’s various operating modes; continuous; single measurement; wake up on change and burst mode. The “wake up on change” feature detects a change in the magnetic status and returns the device to measurement mode in around 500 µsec. In addition, the device’s settings can be adjusted at runtime as required by the application needs. The burst mode duty cycle programmable range spans between 0.1% and 100%. By having it higher, fast response time applications can be served. Conversely, by having a lower duty cycle the current consumption can be curbed at supply voltages as low as 2.2V.

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