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UCC3818: App note about light load operation of UCC3818?

Andrew Massey
Prodigy 120 points
Part Number: UCC3818

Hi,
Figure 2 page 2 of the below App note shows R1, R2 and Q1....the idea is that Q1 turns off when VAOUT goes less than 1V...but would you agree, the circuit shown could not reliably do that.....instead a comparator would be needed, would you agree?

App note, fig 2 , page 2

  • 0
    TI__Mastermind 19545 points

    Hi Andrew,

    Thank you for the query on UCC3818.

    The circuit based on R1, R2 and Q1 only contributes to the bias current at light load condition when the VAOUT voltage i slightly greater than 1V where Q1 is gated off and bias current is added from the REF pin. Now in heavy load when VAOUT is high, Q1 is turned on, so there will be no effect of the bias resistor. I don't think a comparator is needed.

    Regards,

    Harish