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UCC3895: How to stop the device if there is no external pulse on the SYNC pin?

Part Number: UCC3895


In this device, the frequency of the oscillator inside the device is determined by the constants of the parts mounted on the 7-pin CT and GND, and the 8-pin RT and GND.
I have SYNC input a 270kHz pulse waveform from the outside for synchronization.
In this case, if no external pulse waveform of 270kHz is input, the device operates at the frequency of the internal oscillator.

Is it possible to disable the oscillator inside the device if no external 270kHz pulse waveform is input?
For example, if the parts between CT and GND and RT and GND are not mounted, will the internal oscillator stop working?

Best regards,

  • Hello,

    Even when you are synchronizing the RT and CT components need to be populated.  You generally set the frequency to 80% of the sync frequency.  If you want to disable the device pull the soft start pin to ground.