Quick circuit: low voltage inrush limiter (USB?)

[c4757p]

A lot of the circuits I see floating around online for doing inrush current limiting, perhaps for a finicky interface like USB, are either overcomplicated or stupid. Some even in manufacturers' app notes don't really work. Thought I'd write up and share a circuit I've been using a lot lately that works about perfectly for this:

FET Inrush Protection

It's fairly simple, so I'm sure I'm not the first to do it quite like this, but hopefully I can post this and bring up the SNR on this particular topic a bit

[T3sl4co1l]

Well, one of those USB power switch thingers does everything: active current limit (if imprecise), hiccup or latched fault mode, thermal limit, the works.

Neither of the discrete examples are actually "current limiting", they just fake it by being slow.  I don't think FTDI has much in the way of analog engineers, and EDN...what did you expect?

Tim

[c4757p]

Fair enough

[Jeroen3]

I've found the MIC20XX family to look promising. Not expensive and they have a lot of different configs.
Unfortunately, I never got around to use one since the specs of the project did change.

[c4757p]

Yeah, that's a nice-looking chip - definitely will put that on my list

[Howardlong]

Depending on what you're doing, the USB3751-1 might be a solution.

This offers a ton of features particularly for USB devices with rechargeable batteries, including charging port identification and capabilities, under- and over-voltage protection and ESD protection. It also offers 100mA current limit until configured otherwise.

They're not cheap ($0.44 1ku) but depending on the application, once you've added up the cost of all the other paraphernalia using discrete devices, it might be an economically viable solution.

[BravoV]

Perfect for my need with the excess of fets lying around, and appreciate the writing, thanks ! 

[dadler]

Clever, and very professionally presented. Archived for later reference. Thanks!