The MLX90285 is a one-chip solution for driving two-coil brushless DC cooling fans.
Based on mixed-signal CMOS design, the device includes Hall-effect sensor with offset cancellation scheme, voltage regulator, digital logic and power output drivers in a single package.
The device features Soft Switching to lower acoustic and electrical fan noise. This efficient solution is enhanced with an intelligent "Active Slope Control" which automatically adjusts the slope duration depending on the fan rotation speed. Thus, the fan performance to noise ratio is always kept optimum without the need of tuning via external component.
The MLX90285 FG-Version has an open-drain tachometer FG output that follows the Hall signal. This signal is used by hardware monitoring system to determine the rotation speed of the fan.
In the MLX90285 RD-Version, the open-drain alarm output RD is a safety signal which allows detecting if the fan rotates or not. The built-in locked rotor protection automatically shuts off the coil current when the rotor is mechanically blocked for more than 0.43 second. The fan tries to restart every 3 seconds until the rotor is released. This on/off cycling reduces the average current by factor of about 7. This protection prevents the fan to be overheated or damaged.
The MLX90285 is a no-VDD fan driver. Thanks to the patented no-VDD concept, integrated FG- and RD- options are available in a 4-pin through-hole package (TO92) and 8-pin surface mount Small Outline Integrated Circuit (SOIC) package.
Two different product versions are available:
- MLX90285 FG-Version (Frequency Generator)
- MLX90285 RD-Version (Rotation Detection)