CUI DEVICES | SERIES: CFM-40C | DESCRIPTION: DC AXIAL FAN

date 08/12/2022 | page 6 of 7

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APPLICATION NOTES

Tachometer Signal (Yellow Wire)

The tachometer signal is for detecting the rotational speed of the fan motor. The output will be a square wave when fan is operating and

VFG or VCE depending on the locked rotor position when fan motor is locked (See Figures 1~2 below).

Figure 1: Tachometer

Output Circuit

Figure 2: Tachometer

Output Waveform

Polarity Protection

Able to withstand 10 minutes of reverse polarity connection between the positive and negative wires without causing damage.

Output Type: Open Collector

Vs: (VFG)

5 V fan: 3.3~5 V

All others: 3.3~15 V

Ic≤5 mA

R≥Vs/Ic

VCE(sat)≤0.5 V

4 Pole Motor

N=RPM

T=60/N (sec)

FG=1/T*2 (Hz)

N=FG*30

PWM Duty Cycle (%) = T1/T x 100%

PWM Frequency Range: 20~30 kHz

PWM VIH = 2.8~5.5 V

PWM VIL = 0~0.6 V

Figure 3: PWM Input Signal

PWM Signal (Blue Wire)

This wire is for speed control of the fan motor using a PWM input signal from the customer circuit (See Figure 3 below).

Additional Resources: Product Page | 3D Model