![]() ![]() USB cables are generally standard type-A on one end and either type-B, Mini-B or Micro-B on the other. The outer pin-1 is positive and pin-4 is negative. Pin 2 (D-, white wire) and pin 3 (D+, green wire) carry dataīesides the standard type-A and type-B configurations with 4 pins, there are also the USB Mini-A, Mini-B, Micro-A and Micro-B that include an ID pin to permit detection of which cable end is plugged in. The housing connects to the ground and provides shielding. Pin 1 carries +5VDC (red wire) and 4 is ground (black wire). When charging a battery, these pins have no other function than to negotiate current.įigure 1: Pin configuration of standard A and standard B USB connectors, viewed from the mating end of the plugs The two shorter pins, 2 and 3, are marked D- and D+ and carry data. Pin 1 delivers +5VDC and pin 4 forms the ground that also connects to the shield. Standard A and B USB plugs, as illustrated in Figure 1, feature four pins and a shield. The advantage: Li-ion will last longer if not fully charged. This is a minor problem the battery will only charge to about 70 percent state-of-charge and deliver a slightly shorter runtime than with a fully saturated charge. (See BU-409: Charging Lithium-ion) Due to the voltage drop in the cable and connectors, which is about 350mV, as well as losses in the charging circuit, the 5V supply may not be high enough to fully charge the battery. Charging a 3.6V pack begins by applying a constant current to a voltage peak of 4.20V/cell, at which point the voltage peaks and the current begins to taper off. The original USB port can only charge a small single-cell Li-ion battery. To prevent overload, some hosts include current-limiting circuits that shut down the supply when overdrawn. Charging a device that draws 500mA connected together with other loads will exceed the port’s current limit, leading to a voltage drop and a possible system failure. There is, however, a danger of overloading a USB hub when attaching too many gadgets. With 5V and 500mA available on version USB 1.0 and 2.0, and 900mA on USB 3.0, the USB can charge a small single-cell Li-ion pack. The host cannot take power from an outside source. ![]() Data streams in both directions but the power is unidirectional and always flows from the host to the device. The USB port can also be used to charge personal devices, but with a current limit of 500mA on the original design, this might have been an afterthought.Ī typical USB network consists of a host that is often a PC and peripherals such as a printer, smartphone or camera. Compaq, DEC, IBM, Intel, NEC and Nortel contributed to the developments with the goal of simplifying the interconnection of peripheral devices to a PC, as well as to allow a greater data transfer rate than was feasible with earlier interfaces. To learn more about how and for what purposes Amazon uses personal information (such as Amazon Store order history), please visit our Privacy Notice.The Universal Serial Bus (USB) was introduced in 1996 and has since become one of the most widespread and convenient interfaces for electronic devices. You can change your choices at any time by visiting Cookie Preferences, as described in the Cookie Notice. Click ‘Customise Cookies’ to decline these cookies, make more detailed choices, or learn more. ![]() Third parties use cookies for their purposes of displaying and measuring personalised ads, generating audience insights, and developing and improving products. This includes using first- and third-party cookies, which store or access standard device information such as a unique identifier. If you agree, we’ll also use cookies to complement your shopping experience across the Amazon stores as described in our Cookie Notice. We also use these cookies to understand how customers use our services (for example, by measuring site visits) so we can make improvements. ![]() We use cookies and similar tools that are necessary to enable you to make purchases, to enhance your shopping experiences and to provide our services, as detailed in our Cookie Notice. ![]()
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