UF2768

Preliminary

CMOS IC

UNISONIC TECHNOLOGIES CO., LTD

6 of 8

www.unisonic.com.tw

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FU N CT I ON AL DESCRI PT I ON (Cont .)

Soft Switch (Sine-Wave Output)

The is a soft switch function to make phase current be-come more gentle, which can reduce the noise of motor in

switching interval. Using PWM duty cycle control to create the sinusoidal current waveform. BEMF detection window

is opened on phase W in order to measure the rotor position so as to define the modulation timing. close to the ideal

sine wave output.( See figure 4. Sinusoidal PWM)

Lock Protection and Automatic Restart

The UF2768 provides the lock protection and automatic restart functions to prevent the coil burnout while the fan

is locked. As the fan is locked, the IC will come into startup operation for 1 second. Then, the IC will switch to lock

protection mode to close output driver for 6 seconds. After lock protection mode, the IC switches to startup operation

again. If the locked condition still remains, the lock and restart process will be recurred until the locked condition is

released.

Thermal Protection

The UF2768 has thermal protection. When internal junction temperature reaches 160°C, the output devices will be

switched off. When the IC’s junction temperature cools down 30°C, the thermal sensor will turn on the output devices

again, resulting in a pulsed output during continuous thermal protection.