View Full Version : What are the output parameters of the USB connector of G551 "charger" USB port?

05-13-2015, 08:55 PM
What are the output parameters of the USB connector of G551 "charger" USB port?
I want to know the amount of ampers/mAh I can receive from that special USB designed for fast charging.

05-13-2015, 09:57 PM
Specifications for USB 1.x, 2.0, and 3.0 require constant 5V power at 100mA for unenumerated devices, up to a maximum of 500mA for enumerated devices which request it. USB's official Battery Charging Specification 1.2 appeared on some later (post-2010) USB 2.0 devices and some USB 3.0 devices, it allows power delivery of up to 1.5A while maintaining USB 2.0 High Speed data transmission, or up to a maximum of 5.0A as a raw power source without any (post-enumeration) dataflow. Some USB 3.x variants support Low-Power (max 150mA) and/or High-power (max 900mA) modes while transmitting data. USB-C (a variation of USB 3.1 which uses a new non-backwards-compatible connector) is the latest and greatest USB now/soon available, and appears to have a more complicated (up to 5V 3A) power delivery system designed to accommodate direct internal connections with DisplayPort, Thunderbolt, Ethernet, and other devices.
Wikipedia's USB article (http://en.wikipedia.org/wiki/USB) sums it all up well enough, and every official USB specification/standard is available for download at the USB Implementers Forum (http://www.usb.org/).

Low-Power ports typically appear on things like laptops, mobile devices, and unpowered (hub-powered) USB hubs. High-Power ports typically have different visual markings or appearance to clearly set them apart from "standard" USB 2.0 black and USB 3.0 blue ports, I've seen white and red and obnoxiously radioactive neon green variants.

Your motherboard/laptop (or related documentation for it) will clearly state which generation USB controllers/ports are onboard. USB 2.0 is basically the common default these days, so any USB 3.x or advanced (better than USB 2.0) power/charging/performance/transfer capabilities will be proudly advertised (somewhere) as a major selling point for the product. USB 3.0 ports are almost always coloured with that obnoxious "Pantone Blue 300C" which is recommended within USB 3.0 standards, and the usual USB FullSpeed/HighSpeed/SuperSpeed symbols are almost always found printed within immediate proximity of the USB ports.

Almost all modern smartphones and tablets have integrated self-resetting "thermal fuses" or power regulators which will allow them to connect to a power input up to at least 2A, even if they actually only use 500mA or less at full charging capacity. This is because device manufacturers like avoiding potential lawsuits involving the use of their devices with (unregulated) products like automotive USB chargers, etc. You won't blow up any modern device on a modern USB port simply because it won't deliver more than minimal (100mA) power until the connected device properly enumerates itself and requests more power, and it won't deliver more power than requested. And you can always use a USB cable with an inline fuse for extra protection, if you like. USB is now a mature technology, all the simple problems have been solved pretty well.

05-22-2015, 02:41 PM
Thank you for reply.

I have checked it's user manual, and there is nothing written about amps or even voltage. I'm asking about the special "charging" USB port, located at the left of the laptop. While all USB ports are 3.0, what is the difference with this special one? I want to know it's amp/mAh value.

05-23-2015, 02:37 AM
The actual power output of that port (or the specific USB standard for that port) will be specified somewhere in your product documentation. Or you could measure it with a DMM, but that likely won't show more than 5V@100mA until an enumerated USB function is plugged in and requests (and is given) more power from the USB controller.

Again, the USB port won't "overcharge" a USB device with more power than it can handle. USB standards won't allow it.