Melexis – MLX90393: Melexis Unveils Software-Defined Sensor

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Ultra flexible, magnetic sensing solution gives engineers carte blanche in HMI implementation through breadth of programmable parameters.

The MLX90393 is a micropower triaxis magnetometer and is offering maximal flexibility at minimal size. With its 3 x 3mm footprint, it can fit in the tiniest of assemblies. It provides a digital output proportional to the sensed magnetic flux density along the 3 perpendicular axes of symmetry of the sensor. But the miniature sensor is mostly characterized by the fact that it can interchange measurement speed for both current consumption and noise on the digital output signal, making it the raw building block for any magnetic sensing application up to +85°C. An external microcontroller can then combine the measurement data in order to define the position of the magnet with respect to the sensor. All that at a selectable duty cycle of 0.1% to 100%.

  • Micropower (2.2V to 3.6V, <5μA idle current)
  • Low voltage I/O (1.8V – VDD)
  • SPI (3+4-wire) and I2C interface, slave node
  • 16-bit XYZ magnetic and T thermal measurement
  • QFN 3 x 3 package, 16-leads
  • In-application programmable (gain, mode, axes, …)
  • Ta = -20°C to +85°C

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APPLICATIONS

  • Sensing element for the Internet of Things (IoT)
  • Metering
  • Impeller-based meters 360° impeller position detection incl. anti tampering
  • Meter mechanical counter digit readout
  • General triaxial anti tampering detection
  • Gauss-meter
  • HMI
  • Joystick with push
  • Rotary knob with push
  • Lever/slide switch linear stroke
  • Valve position, industrial sensing
  • Robotics and factory automation

Human Machine Interface (HMI)
The MLX90393 lends itself to a wide variety of HMIs such as joystick (Gimball, Ball&Socket) with push detection, rotary knobs with push function and linear strokes by levers or sliding switches. The sensor output data needs to be post-processed in order to calculate the angles or norms of the vector in order to get the desired position signal(s). This requires off-chip computation, and is a clear advantage in system level partitioning by having one microcontroller interfacing with many sensors on the same bus.

The MLX90393 supports 3 different operating modes:
1. Single measurement mode

  • Command-based
  • Trigger-based

2. Burst mode
3. Wake up on change mode

In single measurement mode, a bus master is requesting the sensor to perform a measurement, either by transmission of a command, or by issuing a trigger signal.

Whenever the sensor is in burst mode, it is waking up and going back to sleep at an in-application programmable duty cycle.

Finally, the wake up on change function offers the same functionality as the burst mode, but only setting the interrupt pin high whenever the latest measurement differs more than a programmable threshold from either the previous measurement or the first measurement when entering the mode.

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