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UCC28C42: External Oscillator directly to the RT/CT pin - dead time vailations?

HAREL LEVY
Prodigy 250 points
Part Number: UCC28C42
Other Parts Discussed in Thread: UCC2806

Hi Everyone,

I'm using the UCC28C42 Peak Current Mode Controller and I tie the RT/CT pin directly to the output of the external clock (it can handle the sink current of the controller).

Can I drive the RT/CT with a 50% duty cycle?

Will the internal oscillator clip the time duration of the external oscillator?

If we take for example the UCC2806 the duration of the sync controls the time both output are off. does the same happen here wit the UCC28C42?

Thank you.

  • 0
    TI__Mastermind 33115 points

    Harel,

    Internal oscillator initiates OUT pulse at  RAMP valley and terminates the OUT pulse at RAMP peak. The RT/CT is selected to set the oscillator frequency lower than the external SYNC frequency (typical is about 20% lower). The pulse termination is edge triggered and latched internally so you should be ok. You can also try running one of the simulation models available in the UCC28C42 product folder.

    Regards,

    Steve M