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ucc 28700 not able to give initial three pulse

anchal vijay
Prodigy 50 points
Other Parts Discussed in Thread: UCC28700

in order to see ucc28700 functioning ,i have connected cs pin and cbc pin to the ground and applied 21 v to Vdd pin.

i am able to recieve  only one pulse.but accordind to datasheet i should get three pulses.

  • 0
    TI__Expert 4015 points

    The IC looks for a change in slope on the Vs pin voltage to terminate the off time. This change in slope is called the Demagnetisation ring becuase it happens when the flux in the core has been depleted and the core is demagnetised. If there is nothing connected to the Vs pin and the IC does not see this ring, then it will not switch.