3 ms·
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
by mcshicks 2y ago
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.
- amelius 2y agoI'm looking more for a solution that acts as a constant current source, but where the voltage never exceeds the input voltage.
- tomooot 2y agoAMC7135 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.
- amelius 2y agoThank you for the suggestion, but it seems that the device has no over-temperature protection.
- ssl-3 2y agoIf 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?
- mcshicks 2y agoI 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.