>I built his basic SMPS circuit and I'm seeing some behavior
>that I cannot explain.  It basically works but it is only
>switching in repetitive bursts. The period of the bursts
>varies with the size of the output filter capacitor.

This sounds like you have too small a load on it. Increase the current draw
until it stops chirping, and then see what current draw you have. You may be
able to get away with a smaller capacitor if you are after really low
current draw.

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