USB Connectors: Increasing Power Requirements - Page 1
Forum section: electronics / general

author: PeteH
author_rank: Unknown
timestamp: November 29, 2011, 08:46:00 pm
content: I am starting to see a lot of USB chargers rated for >1.5A per port (port specifically; 2.0~2.4A). The market is driving these new requirements as a result of the tablet upswing.A simple question; I have not seen a USB receptacle (USB - A, Through-hole) that can accommodate this level of current? Even USB 3.0 receptacles are normally rated at 1.8A Max? Remember the assumptions that go along with utilizing a connector at rated current (layout, wire gauge, etc). (embedded: let me know if you find one. . . )How are these manufacturers (OEM, Belkin, etc) getting away with pushing well above rated current through these connections? (heat sinking the ports, speciality connectors?)Maybe I am missing something...

author: Short Circuit
author_rank: Frequent Contributor
timestamp: November 30, 2011, 01:03:32 am
content: Quite simple; they determine their requirements and then contact suppliers to provide an suitable part. Manufacturer checks if they can get away with it and provide written approval. In case of big customers like Apple, they probably perform UL testing as well.Even if no part can be approved, some small changes like higher temperature plastics to handle the 33% additional heat, or perhaps slightly thicker contacts to reduce the nominal contact resistance by 33% will do the job. After all, the step from 1.8 to 2.4 amps is not that big.

author: corona
author_rank: Newbie
timestamp: November 30, 2011, 01:30:34 am
content: I would have thought the bigger issue would be the USB cables, they're certainly not going to be rated for the higher currents, I've seen plenty of ones out there with hair thin conductors.

author: Short Circuit
author_rank: Frequent Contributor
timestamp: November 30, 2011, 02:28:20 am
content: No issue at all; if you order your cables with #20 AWG power conductors, then that's what you'll get.But that is not standard, so you'd have to buy enough to match the custom raw cable moq, usually somewhere between 1000-5000 meters.

author: IanB
author_rank: Super Contributor
timestamp: November 30, 2011, 06:15:57 am
content: Manufacturers are definitely pushing the limits. I recently found when I tried to play Angry Birds on my iPhone while simultaneously charging the battery that the charger overheated and activated the thermal cutout. At least I now know that the iPhone chargerdoes havea thermal cutout and won't simply melt or smoke when overloaded...

author: BravoV
author_rank: Super Contributor
timestamp: November 30, 2011, 06:19:35 am
content: ipad charger specifically stated and written at the adaptor that its generating 2.1 Amp at 5.1 Volt at it's output which is using usb connector.

author: bfritz
author_rank: Regular Contributor
timestamp: November 30, 2011, 10:32:41 pm
content: I looked at this in detail several months ago as part of a charging product I was working on.Most of the connectors I looked at specified the current on all terminals at 1.5A. The truth is that even in a 2A charging product, only two of the terminals would be at 2A.Here's a product spec for a Type A that states the specs with all circuits at 1.5A.http://www.molex.com/pdm_docs/ps/PS-48037-001.pdfSince this is not the way you'll use the part, it will likely work fine at 2A. I go through the calculations below.For example assume a contact resistance of 30mOhms. Taken from the datasheet link above.A connector at 1.5A dissipating power in all 4 circuits would dissipate:P=4*R*I2=4*20mOhm*1.5A2=0.18WA connector at 2.0A dissipating power in only 2 circuits would dissipate:P=2*R*I2=2*20mOhm*2.0A2=0.16WIn my testing I didn't see any problems with the connectors getting too warm.The real issue will be if your product requires approval by a listing agency such as UL or ETL. You can use the connector, but you'll then have to submit the part for testing, and pay the appropriate fee, unless you can get the manufacturer to do it for you.

author: Unknown
author_rank: Unknown
timestamp: November 30, 2011, 10:36:29 pm
content: Quote from: IanB on November 30, 2011, 06:15:57 amWhat a sad sad picture that paints........

author: don.r
author_rank: Frequent Contributor
timestamp: December 01, 2011, 03:50:14 pm
content: Quote from: Uncle Vernon on November 30, 2011, 10:36:29 pmNot really. Nothing wrong with a little diversion.

author: Unknown
author_rank: Unknown
timestamp: December 01, 2011, 08:27:43 pm
content: Quote from: don.r on December 01, 2011, 03:50:14 pmDiversion? I don't think so. While sad indeed, I am still quite sure he wasn't wearing women's clothing or a Nazi uniform at the time.