Melexis launched a really cool driving solution for silent brushless cooling fans. The MLX90285 provides a robust, high performance and fully integrated Hall effect based fan driver IC, including technology lowering both acoustic and electrical noise. This device is ready to serve demanding cooling requirements in office equipment or consumer electronics such as Laser Printers, Projectors or Flat-Screen Televisions.

The MLX90285 features a one-chip solution for driving low noise two-coil brushless cooling fans. It includes all the necessary analog/digital and power electronics on a single piece of silicon, thus greatly reducing external component counts and printed circuit board complexity.

The MLX90285 suits numerous cooling applications as it operates from 5 to 24 volts. The low voltage operation down to 5 volts even allows for use in speed control applications where supply voltage is reduced to lower the cooling fan rotation speed. Melexis very robust and quality-oriented design eliminates cooling fan designer’s worries about lack of safety margins since the device is even able to operate within an ambient temperature from -40 to 150 degree Celsius. Therefore, the high operating temperature makes the device attractive also for industrial or automotive applications.

Imagine watching an intense moment of the latest action movie on high-definition television (HDTV) or home-cinema projector. Would you really enjoy the experience having a noisy cooling fan operating at the same time? The MLX90285 integrates on-board soft-switching technology for effective acoustic and electrical noise reduction. During normal operation, a fan motor coil tends to behave as a “buzzer” when coil current flow is rapidly changed, and so generating an audible “click” noise. The soft-switching concept primarily consists in smoothing the coil current change via a more complex slew rate control of the power stage. Since the power stage is also fully integrated in the MLX90285, all the complexity is kept in the chip while all the simplicity is given to the customer.

A potential drawback of the soft-switching is a reduction of motor efficiency. “Passive” soft-switching techniques apply a fixed output slew rate, independent of the fan rotation speed. While such passive solution could still bring acceptable low noise results, it could likely reduce the motor efficiency. The MLX90285 provides an “Active” soft-switching technique which automatically adjusts the applied output slew rate depending on the fan rotation speed measured via the built-in Hall sensor. Thus high motor efficiency and low noise are reached at high rotation speed, while even lower noise is achieved at low rotation speed.

The MLX90285 is available in two versions for the logical open drain output type: either Tachometer (FG – Frequency Generator) output used for rotation speed computation, or Alarm (RD – Rotation Detection) output used as a safety signal for no-rotation detection. The device provides as well built-in locked rotor protection to prevent motor coil overheating in case of mechanical blockage. Thermal protection is also included to best protect the device against abnormal temperature rise caused by motor coil short-circuit. Last and not least, high electrostatic discharge (ESD) rating of more than 4000 volts (Human Body Model) delivers a comfortable safety margin against potential risks of damage during module assembly or usage.