I bought one of those 10 packs of 1,400ma regulators from DX that is populated with 4*AMC7135. I'm planning on wiring 2 in parallel like many people do for a basic regulator in a P7 upgrade to a 2C MagLite.
I downloaded a pdf from ADDtek on the AMC7135. I'm not sure if there's more than one manufacturer of these. On page 1 of the manual there is a diagram called, "TYPICAL APPLICATION CIRCUIT". In the diagram is an asterisk saying, "CO is strongly recommended". CsubO is a capacitor wired from the negative output of the 7135 to ground. Here is another quote from page 4, "If LED and AMC7135 is located in separate PCBs, or the length of the routing path L1>10cm or L2>3cm, the output capacitor CO should be added. Typically, capacitance of 0.1uF ~ 1uF is recommended and 1uF is needed when L2 is much longer than 3cm". For clarification, L1 is the length of the wire from the positive side of the battery to the positive side of the LED. That could easily be under 4 inches. L2 on the other hand is the length of the run from the 7135's negative output to the negative side of the LED. That's less than 1¼ inches from chip to LED. I think it's safe to say that every Mag mod I've seen fails at least 2 of the 3 conditions to their test for the capacitor's necessity. Namely the negative lead to LED being longer than 30mm and the 7135 chip not being mounted on the same PC board as the LED.
So my question to the electronics guys is what is this capacitor for and why is it necessary? If nobody uses it and that without incedent, how necessary can it be?