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Information & Troubleshooting
- USB Power supply General voltage specifications of USB hubs, etc.
- USB Solutions How to solve various problems of USB devices used with Microsoft operating systems
A connection according to USB 1.1 or USB 2.0 specifications operates in the following manner:
- 5V DC voltage
- up to a maximum of 500mA
- some portable laptop computers only offer 100mA'
- inner polarity of plug (+)
- 5V DC
- max 900mA
- PCIx/Expresscard/etc.must have Powerconnector, because the Mainboard slot does not support 5V1,8A for 2-Port USB3.0 Devices.
So-called y-USB cables offer the function to deliver electricity of up to 1A to external hard disk drives or to other USB devices. Yet, USB connectors are often bridged, which means that both connectors feature power of 500mA, each. This is more frequently the case in laptops, and as a result the use of such a y-USB cable will not work in these cases.
A y-cable differs from other cables in the way that one of the plugs can not be used for data transfer, for it functions solely as a means of supplying a device with power. If problems occur whenever you use y-USB cables this means, of course, that you have to use a separate power supply if the device supports additional power supplies.
Standardized USB mainboard connectors
P-7: Data - (also called D- in cases of European versions of mainboards)
P+7: Data+ (also called D+ in cases of European versions of mainboards)
GND: -5V/ground connection with PC chassis
Please note: If a voltage reversal occurs or if the USB pin assignment is mistaken your computer will usually shut down automatically. In rare cases, however, components of your mainboard might irreversibly be destroyed.
Device connection to establish connections with the USB mainboard connector
Black/Ground: Supply voltage minus Red/+5V: Supply voltage plus White/-D: Data bus minus Green/+D: Data bus plus
- DA-70138-2 (internal SATA and USB connections, all other connections must be connected in an external way with the mainboard)
Please note: It might happen sometimes that a PC does not start up anymore if voltage supply is used simultaneously via the black/red cables AND via the power connection with the power supply. Then it is necessary to change your BIOS settings.
USB 3.0 Controller is not bootable
The first generation of USB 3.0-Chipsets from NEC, (used in all available USB 3.0 Controllers) are not bootable. If NEC or other Chipsetmanufactorer builds bootable USB3.0 Chipsets, we will provide these as DIGITUS® Article.