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The STL6900A series is an advanced open-loop direct PWM driving type DC brushless fan driver.

The device supports direct PWM input to eliminate the circuit for PWM to DC conversion, thus reduce the external component count. Friendly design allows external resistor divider to adjust the highest and lowest speed presetting, furthermore, the same method using voltage divider is built-in to adjust the slope of fan speed curve. Meanwhile, the device provides direct PWM outputs at frequency at 25kHz to support a single-phase full-wave driving of a motor coil.

The STL6900A series is designed in a soft-start feature with incremental duty cycle from 10% to 40% to further smooth-out the power-up spike on the coil current, thus reducing the start-up noise and relaxing the power budget. Other important function such as current limiting, internal voltage reference output and etc are also supported for fan control application.

The devices support automatic lock detection and cease the output current. Once the external stop force is relaxed, the devices automatic recover to the previous speed. Various open-drain output types of RD or FG are implemented as the tachometer for system to monitor the speed of a DC fan motor fan speed.

  • Variable speed DC brushless fan for desktop CPU cooler.
  • Variable speed DC brushless fan for sever/telecom system.


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