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Comment by mcshicks | Hacker News Reader

You can use inductors. Some USB cables have a choke on them. But basically the problem is when a large amount of circuitry all powers up at one when you plug in. So everything connected directly to USB 5v with a lot of large capacitors to filter the power. If you really need that then you can self power and avoid the problem.

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If the answer to excessive in-rush current (due to capacitance) is to add series inductance, then: Isn't the more-efficient answer simply less capacitance?

I think the correct answer really depends upon what you are trying to do. Sometimes where board space and cost are not an issue people use a combination of larger and smaller bypass caps to reduce switching noise. I don't think there is a one size fits all solution because people power many different types of things from USB. It's more just a caution about USB power in general. Most people know the 500mA current limit, but in-rush compliance is something you don't really see in functional testing because typically you can get away with a violation and the board will still work.

I'm looking more for a solution that acts as a constant current source, but where the voltage never exceeds the input voltage.

AMC7135 might work: it's a linear LDO fixed current regulator designed for driving LEDs, which internally is basically an N-channel MOSFET which holds it's gate voltage in the linear region and actively adjusts it to provide constant current.

Thank you for the suggestion, but it seems that the device has no over-temperature protection.

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