Browse Prior Art Database

Increasing USB Current by Sharing Data Pins as Power Pins

IP.com Disclosure Number: IPCOM000207824D
Original Publication Date: 2011-Jun-13
Included in the Prior Art Database: 2011-Jun-13
Document File: 3 page(s) / 241K

Publishing Venue

Motorola

Related People

Calvarese, Russ: INVENTOR [+2]

Abstract

USB connector types have become smaller as devices like tablet computers, PDAs, mobile phones become smaller. Example connector types include micro and mini USB. The small size of these connectors makes it difficult for them to carry high currents without exceeding acceptable temperature limits. This is often the limiting factor that determines how quickly a device can be charged and how much current is available to operate the device while it is being charged. During periods when the data pins are not needed to pass data, they can be used as power pins to nearly double the current before the connector’s rating is exceeded.

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Increasing USB Current by Sharing Data Pins as Power Pins

By Russell Calvarese, Robert Sandler

Motorola Solutions

 


ABSTRACT

USB connector types have become smaller as devices like tablet computers, PDAs, mobile phones become smaller. Example connector types include micro and mini USB. The small size of these connectors makes it difficult for them to carry high currents without exceeding acceptable temperature limits. This is often the limiting factor that determines how quickly a device can be charged and how much current is available to operate the device while it is being charged. During periods when the data pins are not needed to pass data, they can be used as power pins to nearly double the current before the connector’s rating is exceeded.

PROBLEM

When operating from a dedicated AC power adapter/charger, existing mini/micro USB connectors have maximum current limits for each pin that do not allow for as much current as we would like to power the device while charging internal batteries. Typically D+ and D- is shorted with a resistor in the dedicated charger then detected by the device. The device can then draw over 100mA without enumeration. Exactly how much current that can be drawn by the device varies for different USB standard versions but the pin current rating can never be exceeded. Existing micro/mini USB jacks are rated 1A to 1.8A continuous. Some allow for higher peak currents. Recent tablet and LTE WWAN devices require upwards of 4A to allow full charge without restricting operation.

SOLUTION

USB pin sharing is a way to double the available current by sharing the data pins as power pins. If more than 2X current is needed than some reduction in charge current or function must be designed in. There are many ways to indicate and detect the charger has the ability to switch the data pins to charge pins. The scheme could be as simple as a known resistor value that is detected by an inexpensive comparator or more elaborate schemes that might prove more reliable. Once the charger signals its ability to switch the data...