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An Automotive Head-Up Display (HUD) is a driver assistance system intended to reduce distractions by allowing drivers to check on important trip information without looking away from the road.

Information typically shown include current speed, navigation directions, engine RPM, or even “augmented reality” overlays, such as the safe following distance to the vehicle in front, the speed limit on that stretch of road, or collision danger alerts.

Given their usefulness and the increased safety, these displays are becoming more and more available in production cars and also as after-market products.

There are currently two approaches to HUD: The first requires treating the inside surface of the windshield, whilst the second uses a separate transparent combiner. A complex system of lenses and mirrors projects a computer-generated image onto the windshield or combiner. The projected image is then displayed in front of the driver, who is then able see both the road and the display at the same time.

In both cases, the system requires very accurate positioning of the projection unit, usually achieved by means of a stepper motor.

This solution kit lets developers evaluate ST’s most recent automotive stepper motor driver and achieve best-in-class movement smoothness and positioning precision. 

It includes the EVAL-L99SM81VY, an evaluation board designed to drive one bipolar stepper motor in micro-stepping mode together with coil voltage measurement for stall detection. The motherboard, based on SPC56 microcontroller, provides the logic section for monitoring and driving the L99SM81VY assembled on the daughterboard.

With the aim of making the board usage and settings simpler, ST provides dedicated user-friendly software with a Graphic User Interface (GUI). This enables the user to set L99SM81V parameters and at the same time to get real time information from the device, such as voltage measurements, main power supply voltage, fault flags, device junction temperature and much more.

  • Resolution up to 64 micro-steps per electric cycle allows best in class position accuracy
  • Embedded LDO allowing cost saving on system solution
  • Higher current accuracy
  • Analog Temperature feedback for flexible application protection
  • Up to 1.35 A current capability
  • Integrated ADC for coil voltage measurement and stall detection
  • Very low current consumption in standby mode (typ. 10 µA)
  • Thermal warning and shutdown

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