The specific case I have is a device that draws about 20mA at 12V during operation. I'm using a Littelfuse 0437.500WR which is rated for nominal 500mA. However, the circuit has a 10µF input filter capacitor, and when it's powered from a lowly wall-wart supply, the peak surge current is over 9A for little 200nS bursts. The Littelfuse specs only say it's rated for 350% overcurrent up to 1 second, so only 1.75A, and their graph bottoms out at 1ms (maximum 4.5A). It [em]seems[/em] to work fine, but I can't be sure it actually is okay. Is this just a normal thing that one must accept?
I was fiddling with putting 10Ω in series (figuring it would limit inrush current to 1.2A at the full 12V but only drop 0.2V at normal operation) but that causes the internal DC-DC converter to power-cycle, so I can't afford a current-limiting resistor.