I have a circuit in place for the Linear Technology LT3502A switching regulator (datasheet here). To prevent blowing up the whole thing during hot-plugging, I have chosen to add a small parallel ceramic cap and series resistance instead of an unnecessarily large electrolytic. As so:
The LT3502A is the 3V3 output version.
I shall be using
100V rated ceramics (
1206 size) (or perhaps
50V is also okay, to meet the maximum input voltage of
40V for the chip).
I was just wondering what size resistor I should slap on there. I suppose I should be fine with an
My logic being that the maximum output power of my chip at full load (which it will never reach) is
3.3V*0.5A = 1.65W. Multiply that by say, 2, to account for power losses and an additional safety multiplier
(~ 3W). Presuming
VBUS >= 12V (not going to put a
1W resistor there), the worst-case current through
250 mA, implying
0.0625W dissipation. An
0603 rated for 0.125W should be okay, I think? Just making sure not to release any magic smoke :)