On Nov 2, 2011, at 10:32 AM, Mike Hord wrote: > i =3D C*dV/dt. A passable estimate, therefore, is > 2.2u*400/20u =3D 44A. Heh. I did t =3D RC to get an "equivalent" discharge resistance, and =20 V=3DIR to get the resulting current, hoping that "average" and the 1/e =20 factor in the time constant end up balancing each other "close enough." This also results in an answer of 44A... BillW --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .