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Maximun duty of UCC28221.

Kathy Jong
Prodigy 20 points
Other Parts Discussed in Thread: UCC28221

Hi All,

we plan to use

UCC28221 but see that  "Programmable Maximum Duty Cycle Clamp 60% to 90% Per Channel". for interleave forward, we prefer to use Duty 50%(MAX), Does UCC28221 can operate at 50%(MAX) duty?

Thanks.

  • 0
    TI__Mastermind 25130 points

    Kathy,

    The duty cycle limit is set by the internal oscillator which runs at twice the frequency of the outputs. The duty cycle of this ramp generator (see page 11 of the spec) sets the maxmum duty cycle. If on clock cycle 1 the "A" output turns on the duty cycle limit will be the length of the duty cycle of the oscillator but on the following clock (2) cycle.duty.

    Since the minimum duty cycle of the oscillator is 20% of a clock cycle and it takes 2 clock cycles to make a cycle of each of the outputs then this sets the minimum setting of the Maximum duty cycle to 1 clock cycle and 20% of the next or a total of 60% of an output cycle.

    This does not mean that the outputs will always be 60% They can phase back to zero under the control loops command.