Fan Functions

1. Soft Start Function

When power is supplied to the fan, the current gradually increases from zero until the fan reaches its maximum speed and rated current. The maximum startup current equals the free-running current (or, in rare cases, restart after rotor lock). The fan reaches its rated speed within 0–10 seconds.

2. Auto Restart Function

The auto restart function ensures that the fan motor will automatically restart if the blades are blocked. When the rotor is locked, the fan current drops to zero, and the fan restarts after 5 seconds.

3. FG (Frequency Generator, Tachometer Signal) Function

The FG function provides an open-collector output that must be connected to a "pull-up resistor" and the device's input supply voltage. The output is a square-wave tachometer signal that provides fan speed feedback to the system. The maximum collector current is 10 mA. The device ground must be connected to the same ground potential as the fan.

4. RD (Rotation Detection, Locked Rotor Signal) Function

The RD function provides an open-collector output that must be connected to a "pull-up resistor" and the device's input supply voltage. The output is a high or low logic level signal indicating whether the fan is operating normally.

1. When the fan is running, the signal pin outputs a low level; when the fan is locked, it outputs a high level.

2. Alternatively, when the fan is running, the signal pin outputs a high level; when locked, it outputs a low level.

5. PWM (Pulse Width Modulation) Function

The PWM function allows fan speed control using frequency and high/low logic level signals. In this mode, the frequency can be adjusted between 18 kHz and 30 kHz; the high-level voltage range is 3 V–10 V; and the low-level voltage is ≤0.8 V. The fan speed can be linearly controlled by adjusting the duty cycle, up to maximum speed. CS (constant speed), SS (soft start), and CL (current limiting) functions can all be included. An example PWM diagram is shown below.

6. Temperature Control Function

When the temperature control function is enabled, the fan speed is regulated by temperature, with different speeds corresponding to different temperatures. CS (constant speed), SS (soft start), and CL (current limiting) functions can all be included. This function is mainly implemented through the use of a thermistor. A typical control curve is shown below.