PATENT DOCUMENT

Publication Number: US-8898348-B2
Application Number: US-201313762227-A
Country: US
Kind Code: B2

Title: Method and system for detecting connection of a host device to an accessory device

Abstract:
Techniques for detecting connection of a host device by an accessory device are provided. The accessory device outputs a pulsed voltage/current on its power contact and measure the voltage at the power contact in response to the pulsed voltage/current. If the measured voltage reaches a certain value at or after the expiration of a predetermined time, then the accessory concludes that a host device is connected to it.

Claims:
What is claimed is: 
     
       1. A method of charging a host electronic device having insufficient battery power to perform an authenticate process, the method comprising:
 performing a connection detection process by an accessory device to determine if the accessory is electrically connected to a host electronic device, the connection detection process including: outputting a first voltage over a contact in a connector of the accessory device; measuring, at the contact, a voltage as function of time; and determining whether the accessory is connected to the host electronic device based on the measured voltage and time; 
 if the accessory device determines that the host electronic device is not connected to the accessory, terminating output of the first voltage over the contact and repeating the connection detection process; and 
 if the accessory device determines that the host electronic device is connected to the accessory, initiating charging of the host electronic device to enable the host device to perform an authentication process to authenticate the accessory device. 
 
     
     
       2. The method of  claim 1  wherein charging of the host electronic device comprises, by the accessory device:
 enabling a first power path between the accessory device and the host device and delivering a first current level to the host device over the first power path; 
 thereafter, receiving and responding to a request from the host electronic device to authenticate the accessory device; and 
 upon successful authentication of the accessory device, enabling a second power path between the accessory device and the host device and delivering a second current level higher than the first current level to the host device over the second power path. 
 
     
     
       3. The method of  claim 2  wherein the first power path has a first resistance and the second power path has a second resistance lower than the first resistance. 
     
     
       4. The method of  claim 2  wherein the accessory device determines whether the accessory is connected to the host electronic device based on whether the measured voltage at the contact reaches or exceeds a threshold voltage prior to, at, or after expiration of a predetermined time. 
     
     
       5. The method of  claim 4 , wherein the threshold voltage is between 0 and 1.8 volts. 
     
     
       6. The method of  claim 4 , wherein the predetermined time is between 1 μs and 100 μs. 
     
     
       7. The method of  claim 4  wherein the threshold voltage is less than the first voltage and wherein the accessory determines that the accessory device is not connected to a host device if the measured voltage meets or exceeds the threshold voltage prior to expiration of the predetermined time and determines that the accessory is connected to a host device if the measured voltage meets or exceeds the threshold voltage at or after expiration of the predetermined time. 
     
     
       8. The method of  claim 7  wherein when a host electronic device is not connected to the accessory device, performing a connection detection process comprises outputting a plurality of voltage pulses over the contact having a duty cycle of between 0.1 and 1.0 percent. 
     
     
       9. The method of  claim 7  wherein when a host electronic device is not connected to the accessory device, performing a connection detection process comprises outputting a plurality of voltage pulses over the contact having a pulse duration of between 0.01 and 0.001 seconds. 
     
     
       10. The method of  claim 1 , wherein outputting a first voltage includes supplying a current between 10 μA and 1 mA over the contact less than the first current level. 
     
     
       11. The method of  claim 1 , wherein the host device has a dead battery or has no power. 
     
     
       12. An accessory device comprising:
 a first connector including a plurality of contacts, wherein the first connector is configured to connect with a second connector of a host device; 
 detection circuitry coupled to the first connector; and 
 a current source coupled to a first contact in the plurality of contacts, wherein the accessory device is operable to perform a connection detection process to determine if the accessory is electrically connected to a host electronic device, the connection detection process including: outputting a first voltage over the first contact; measuring, using the detection circuitry, a rate of rise of voltage at the first contact; and determining whether the accessory is connected to the host electronic device based on whether the voltage measured at the first contact meets or exceeds a threshold voltage at or after expiration of a predetermined time; 
 if the accessory device determines that the host device is connected to the accessory device, initiate charging of the host electronic device to enable the host electronic device to perform an authentication process to authenticate the accessory device. 
 
     
     
       13. The accessory device of  claim 12  wherein the first current is between 10 μA and 1 mA. 
     
     
       14. The accessory device of  claim 12  wherein the first current is outputted as a series of pulses having a duty cycle of between 0.1% and 1%. 
     
     
       15. The accessory device of  claim 12  wherein the threshold voltage is between 0 and 1.8 volts. 
     
     
       16. The accessory device of  claim 12  wherein the predetermined time is between 1 μs and 100 μs. 
     
     
       17. The accessory device of  claim 12  wherein the accessory device is further operable to:
 prior to the authentication and after detection of the host device, enable a first power path between the accessory device and the host device and deliver a first current level to the host electronic device over the first power path, the first power path having a first resistance; 
 receive and respond to a request from the host device to send authentication information; and 
 upon authentication by the host device, enable a second power path between the host device and the accessory device and deliver a second current level higher than the first current level to the host electronic device over the second power path, the second power path having a second resistance lower than the first resistance. 
 
     
     
       18. The accessory device of  claim 17  wherein the first and second current levels provided by the accessory via the first and second power paths, respectively, are each higher than a current supplied to the first contact during the connection detection process when the accessory device is connected to the host electronic device. 
     
     
       19. A non-transitory computer-readable storage device including a plurality of instructions, which when executed by a controller in an accessory device cause the accessory device to perform a method of determining if the accessory device is electrically connected to a host device having insufficient internal power to perform an authentication process, the plurality of instructions comprising:
 instructions that cause the accessory device to perform a connection detection to determine if the accessory is electrically connected to a host electronic device, the connection detection process including: outputting a first voltage over a contact of an accessory connector of the accessory device; measuring a voltage at the contact as a function of time; and determining whether the voltage measured at the contact meets or exceeds a threshold voltage at or after expiration of a predetermined time; 
 if the accessory determines that the host electronic device is connected to the accessory, instructions that cause the accessory device to initiate charging of the host electronic device by enabling a first power path between the accessory device and the host device and delivering a first current level to the host device over the first power path; thereafter, receiving and responding to a request from the host electronic device to authenticate the accessory device to the host device; and upon successful authentication of the accesory device, enabling a second power path between the accessory device and the host electronic device and deliving a second current level higher than the first current level to the host device over the second power path. 
 
     
     
       20. The storage device of  claim 19  wherein the threshold. voltage is between 0 volts and 1.8 volts. 
     
     
       21. The storage device of  claim 19  wherein the predetermined time is between 1 μs and 100 μs. 
     
     
       22. The storage device of  claim 19  wherein the first current is between 10 μA and 1 mA. 
     
     
       23. The storage device of  claim 19  wherein the second current is smaller than the third current. 
     
     
       24. The storage device of  claim 19  wherein the second current is about 15 mA.

Description:
BACKGROUND 
     Interoprabilty between devices is one of the hallmarks of modern electronic devices. There are many instances where two devices need to work in conjunction with each other to accomplish a particular task. For instance, if a portable electronic device is to be charged, an appropriate power supply is needed that can connect with the electronic device and provide the requisite power to charge the electronic device. 
     Also, often it may be useful to ensure that the two or more devices are connected together before exchanging signals. This may be needed to ensure safety and/or security for the devices involved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a functional block diagram of a host device and an accessory device according to an embodiment of the present invention. 
         FIG. 2A  is an isometric view of a plug connector for an accessory device according to an embodiment of the present invention. 
         FIG. 2B  is front view of the plug connector according to an embodiment of the present invention. 
         FIG. 2C  illustrates contacts of a plug connector according to an embodiment of the present invention. 
         FIG. 2D  is a pinout of a plug connector according to an embodiment of the present invention. 
         FIG. 2E  is a pinout of a plug connector according to another embodiment of the present invention. 
         FIG. 3A  illustrates a receptacle connector for a host device according to an embodiment of the present invention. 
         FIG. 3B  is a cross-sectional view of the receptacle connector according to an embodiment of the present invention. 
         FIGS. 3C and 3D  are pinouts for a receptacle connector according to two different embodiments of the present invention. 
         FIG. 4  illustrates a functional block diagram illustrating connections between a host device and an accessory according to an embodiment of the present invention. 
         FIG. 5  is a high-level block diagram of a power limiting circuitry of an accessory according to an embodiment of the present invention. 
         FIG. 6  is a schematic of an impedance altering circuitry for an accessory according to an embodiment of the present invention. 
         FIG. 7  illustrates circuitry for detecting connection of a host device according to an embodiment of the present invention. 
         FIG. 8  is a graph illustrating relationship between measured voltage and time according to an embodiment of the present invention. 
         FIG. 9  shows voltage/current pulse outputted by the accessory and detection and non-detection of a host device according to an embodiment of the present invention. 
         FIG. 10  is a schematic of an impedance altering circuitry for an accessory according to another embodiment of the present invention. 
         FIG. 11  is a flow diagram of a process for detecting connection of a host device to an accessory device according to an embodiment of the present invention. 
         FIG. 12  is a flow diagram of a process for operating an accessory according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure generally relates to an electronic device and an accessory device that is designed to operate with the electronic device. More specifically, embodiments of the present invention provide techniques for the accessory device to detect connection with the electronic device when the electronic device is powered down or has a dead battery. 
     Some embodiments of the present invention provide a method for detecting connection of an host device to an accessory device. The method includes the accessory device outputting a first current over a contact in an accessory connector. The method further includes the accessory device measuring a voltage as function of time at the contact and determining whether the measured voltage at the contact reaches or exceeds a threshold voltage prior to, at, or after expiration of a predetermined time. If the measured voltage meets or exceeds the threshold voltage prior to expiration of the predetermined time the accessory device concludes that a host device is not connected to the accessory and if the measured voltage meets or exceeds the threshold voltage at or after expiration of the predetermined time the accessory device concludes that the host device is connected to the accessory. 
     Some embodiments of the present invention provide an accessory device that has a first connector including a plurality of contacts. The first connector can be adapted to connect with a second connector of a host device. In this instance, the host device has no power and hence cannot communicate with the accessory device to indicate its presence. The accessory device also includes detection circuitry that is coupled to the first connector and a current source that is coupled to a first contact in the plurality of contacts and can provide a first current over the first contact. The accessory device can output the first current over the first contact, measure, using the detection circuitry, a rate of rise of voltage at the first contact, determine that the voltage measured at the first contact meets or exceeds a threshold voltage at or after expiration of a predetermined time, and based on the determination, conclude that the host device is connected to the accessory device. The accessory device can then communicate with the host device to authenticate the accessory device. 
     Other embodiments of the present invention provide a computer-readable storage device in an accessory device that includes a plurality of instructions. The plurality of instructions include instructions that cause the accessory device to output a first current over a contact of an accessory connector of the accessory device, instructions that cause the accessory device to measure a voltage at the contact as a function of time, instructions that cause the accessory device to determine that the voltage measured at the contact meets or exceeds a threshold voltage at or after expiration of a predetermined time, instructions that cause the accessory device to conclude that the host device is connected to the accessory device, instructions that cause the accessory device to provide a second current over the contact to the host device, instructions that cause the accessory device to authenticate the accessory device to the host device, and instructions that cause the accessory device to provide a third current to the host device over the contact upon successful authentication. In a particular embodiment, the first current is smaller than the second current. 
       FIG. 1  is a simplified block diagram of a system  100  including a host (or electronic) device  102  and accessory  104  according to an embodiment of the present invention. In this embodiment, host device  102  can provide computing, communication and/or media playback capability. Host device  102  can include processing subsystem  110 , storage device  112 , user interface  114 , network interface  116 , and accessory input/output (I/O) interface  118 . Host device  102  can also include other components (not explicitly shown) such as a battery, power controllers, and other components operable to provide various enhanced capabilities. 
     Storage device  112  can be implemented, e.g., using disk, flash memory, or any other non-transitory storage medium, or a combination of media, and can include volatile and/or non-volatile media. In some embodiments, storage device  112  can store data objects such as audio files, video files, image or artwork files, information about a user&#39;s contacts (names, addresses, phone numbers, etc.), information about a user&#39;s scheduled appointments and events, notes, and/or other types of information. In some embodiments, storage device  112  can also store one or more application programs to be executed by processing subsystem  110  (e.g., video game programs, personal information management programs, media playback programs, etc.). 
     User interface  114  can include input devices such as a touch pad, touch screen, scroll wheel, click wheel, dial, button, switch, keypad, microphone, or the like, as well as output devices such as a video screen, indicator lights, speakers, headphone jacks, or the like, together with supporting electronics (e.g., digital-to-analog or analog-to-digital converters, signal processors, or the like). A user can operate input devices of user interface  114  to invoke the functionality of host device  102  and can view and/or hear output from host device  102  via output devices of user interface  114 . 
     Processing subsystem  110  can be implemented as one or more integrated circuits, e.g., one or more single-core or multi-core microprocessors or microcontrollers, examples of which are known in the art. In operation, processing system  110  can control the operation of host device  102 . In various embodiments, processing subsystem  110  can execute a variety of programs in response to program code and can maintain multiple concurrently executing programs or processes. At any given time, some or all of the program code to be executed can be resident in processing subsystem  110  and/or in storage media such as storage device  112 . 
     Through suitable programming, processing subsystem  110  can provide various functionality for host device  102 . For example, in response to a request from accessory  104 , processing subsystem  110  can initiate a buffer transfer session to transfer a data object stored in storage device  112  to accessory  104  via accessory I/O interface  118 . Processing subsystem  110  can also execute other programs to control other functions of host device  102 , including application programs that may be stored in storage device  112 ; in some embodiments, these application programs may include instructions that generate requests to send or receive data objects, and processing subsystem  110  can initiate a buffer transfer session to service any such requests. 
     Network interface  116  can provide voice and/or data communication capability for host device  102 . In some embodiments network interface  116  can include radio frequency (RF) transceiver components for accessing wireless voice and/or data networks (e.g., using cellular telephone technology, advanced data network technology such as 3G, 4G LTE, or EDGE, WiFi (IEEE 802.11 family standards), or other mobile communication technologies, or any combination thereof), components for short-range wireless networking (e.g., using Bluetooth standards), GPS receiver components, and/or other components. In some embodiments network interface  116  can provide wired network connectivity (e.g., Ethernet) in addition to or instead of a wireless interface. Network interface  116  can be implemented using a combination of hardware (e.g., driver circuits, antennas, modulators/demodulators, encoders/decoders, and other analog and/or digital signal processing circuits) and software components. 
     Accessory I/O interface  118  can allow host device  102  to communicate with various accessories. For example, accessory I/O interface  118  can support connections to a computer, an external keyboard, a speaker dock or media playback station, a digital camera, a radio tuner, an in-vehicle entertainment system or head unit, an external video device, a memory card reader, and so on. In some embodiments, accessory I/O interface  118  can include a connector, such as connectors corresponding to the connectors used in various iPod®, iPhone®, and iPad® products, as well as supporting circuitry. The connector can provide connections for power and ground as well as for one or more data communication interfaces such as Universal Serial Bus (USB), FireWire (IEEE 1394 standard), and/or universal asynchronous receiver/transmitter (UART). In some embodiments, the connector provides dedicated power and ground contacts, as well as some number (e.g., four) of programmable digital data contacts that can be used to implement different communication technologies in parallel; for instance, two pins can be assigned as USB data pins (D+ and D−) and two other pins can be assigned as serial transmit/receive pins (e.g., implementing a UART interface); the assignment of pins to particular communication technologies can be negotiated while the connection is being established. In some embodiments, the connector can also provide connections for audio and/or video signals, which may be transmitted to or from host device  102  in analog and/or digital formats. Thus, accessory I/O interface  118  can support multiple communication channels, and a given accessory can use any or all of these channels. In some embodiments, accessory I/O interface  118  can support wireless communication (e.g., via WiFi, Bluetooth, or other wireless protocols) in addition to or instead of wired communication channels. 
     Accessory  104  can include controller  130 , user interface device  132 , storage medium  133 , other accessory-specific hardware  134 , and host I/O interface  136 . Accessory  104  is representative of a broad class of accessories that can interoperate with a host device, and such accessories can vary widely in capability, complexity, and form factor. Various accessories may include components not explicitly shown in  FIG. 1 , including but not limited to storage devices (disk, flash memory, etc.) with fixed or removable storage media; video screens, speakers, or ports for connecting to external audio/video devices; camera components such as lenses, image sensors, and controls for same (e.g., aperture, zoom, exposure time, frame rate, etc.); microphones for recording audio (either alone or in connection with video recording); and so on. In addition, some accessories may provide an additional interface (not shown) that can connect to and communicate with another accessory. 
     Controller  130  can include, e.g., one or more single-core or microprocessors and/or microcontrollers executing program code to perform various functions associated with accessory  104 . For example, where accessory  104  incorporates a user-operable control, controller  130  can interpret user operation of the control and responsively invoke functionality of accessory  104 ; in some instances, the invoked functionality can include sending information to and/or receiving information from host device  102 . 
     User interface  132  may include user-operable input devices such as a touch pad, touch screen, scroll wheel, click wheel, dial, button, switch, keypad, microphone, or the like, as well as output devices such as a video screen, indicator lights, speakers, headphone jacks, or the like, together with supporting electronics (e.g., digital-to-analog or analog-to-digital converters, signal processors, or the like). Depending on the implementation of a particular accessory  104 , a user can operate input devices of user interface  132  to invoke functionality of accessory  104 . 
     Storage medium  133  can incorporate any type of data storage media, including but not limited to disk, flash memory, or any other non-transitory storage medium, or a combination of media, and can include volatile and/or non-volatile media. Storage medium  133  can be used to store program code to be executed by controller  130 , data objects received from host device  102 , and any other data or instructions that may be generated and/or used in the operation of accessory  104 . 
     Accessory-specific hardware  134  can include any other components that may be present in accessory  104  to enable its functionality. For example, in various embodiments accessory-specific hardware  134  can include one or more storage devices using fixed or removable storage media; GPS receiver; a network interface; power supply and/or power management circuitry; environmental sensors (e.g., temperature sensor, pressure sensor, accelerometer, chemical sensor, etc.); and so on. It is to be understood that any type of accessory functionality can be supported by providing appropriate accessory-specific hardware  134 . In some embodiments, accessory specific hardware  134  may include circuitry for detecting connection with host device  102 . In a specific embodiment, accessory specific hardware  134  may include circuitry for detecting connection with host device  102  when host device  102  is powered off or has a dead battery that prevents host device from communicating with accessory  104 . 
     Host I/O interface  136  can allow accessory  104  to communicate with host device  102 . In accordance with some embodiments of the invention, host I/O interface  136  can include a connector that mates directly with a connector included in host device  102 , such as a connector complementary to the connectors used in various iPod®, iPhone®, and iPad® products. Such a connector can be used to supply power to host device  102  and/or receive power from host device  102 , to send and/or receive audio and/or video signals in analog and/or digital formats, and to communicate information using one or more data communication interfaces such as USB, UART, and/or FireWire. Other connectors may also be used; for example, host I/O interface  136  can incorporate a standard USB connector and can connect to accessory I/O interface  118  of host device  102  via an adapter cable. In other embodiments, host I/O interface  136  can support wireless communication (e.g., via WiFi, Bluetooth, or other wireless protocols) in addition to or instead of wired communication channels. 
     Accessory  104  can be any electronic apparatus that interacts with host device  102 . In some embodiments, accessory  104  can provide remote control over operations of host device  102 , or a remote user interface that can include both input and output controls (e.g., a display screen to display current status information obtained from host device  102 ). Accessory  104  in various embodiments can control any function of host device  102  and can also receive data objects from host device  102 . In other embodiments, host device  102  can control operations of accessory  104 , such as retrieving stored data from a storage medium of accessory  104 , initiating an image capture operation by a camera incorporated into accessory  104 , etc. 
     It will be appreciated that the system configurations and components described herein for the host device and the accessory are illustrative and that variations and modifications are possible. The host device and/or accessory may have other capabilities not specifically described herein (e.g., mobile phone, global positioning system (GPS), broadband data communication, Internet connectivity, etc.). 
     Connectors at the respective I/O interfaces  118 ,  136  of host device  102  and accessory  104  can be complementary or not as desired. Where two connectors are not complementary, an adapter (not shown) can be provided to connect the two devices. While connectors may be described herein as having pins, a term generally associated with conventional electronic devices having wires to connect components, it is to be understood that other signal paths (e.g., optical signaling) can be substituted. Further, in some embodiments, some of the connections can be wireless, and connectors can be omitted where wireless interfaces are provided. 
     Further, while the host device and accessory are described herein with reference to particular blocks, it is to be understood that these blocks are defined for convenience of description and are not intended to imply a particular physical arrangement of component parts. Further, the blocks need not correspond to physically distinct components. Blocks can be configured to perform various operations, e.g., by programming a processor or providing appropriate control circuitry, and various blocks might or might not be reconfigurable depending on how the initial configuration is obtained. Embodiments of the present invention can be realized in a variety of apparatus including electronic devices implemented using any combination of circuitry and software. 
     Accessory I/O interface  118  of host device  102  and host I/O interface  136  of accessory  104  allow host device  102  to be connected with accessory  104  and subsequently disconnected from accessory  104 . As used herein, a host device and an accessory are “connected” whenever a communication channel is established between their respective interfaces and “disconnected” when the channel is terminated. Such connection can be achieved via direct physical connection, e.g., with mating connectors; indirect physical connection, e.g., via a cable; and/or wireless connection, e.g., via Bluetooth. 
       FIG. 2A  is an isometric view of a connector  200  that can be associated with accessory  104 . For instance, connector  200  can be implemented as accessory I/O interface  118  of  FIG. 1 . In a particular embodiment, connector  200  can be a plug connector. Plug connector  200  is exemplary and is used herein to explain the various embodiments of the present invention. One skilled in the art will realize that many other forms and types of connectors other than plug connector  200  can be used and that techniques described herein will apply to any connector that has the characteristics of plug connector  200 . In some embodiments, plug connector  200  may be associated with an accessory that can be coupled to a host device. 
     Plug connector  200  includes a body  202  and a tab portion  204 . A cable  106  is attached to body  102  and tab portion  204  and extends longitudinally away from body  202  in a direction parallel to the length of the connector  200 . Tab  204  is sized to be inserted into a corresponding receptacle connector during a mating event and includes a first contact region  208   a  formed on a first major surface  204   a  and a second contact region  208   b  (not shown in  FIG. 2A ) formed at a second major surface  204   b  (also not shown in  FIG. 2A ) opposite surface  204   a . Surfaces  204   a ,  204   b  extend from a distal tip of the tab to a spine  209  that, when tab  204  is inserted into a corresponding receptacle connector, abuts a housing of the receptacle connector or portable electronic device the receptacle connector is incorporated in. Tab  204  also includes first and second opposing side surfaces  204   c ,  204   d  (not shown) that extend between the first and second major surfaces  204   a ,  204   b . In one particular embodiment, tab  204  is about 6.6 mm wide, about 1.5 mm thick and has an insertion depth (the distance from the tip of tab  204  to spine  209 ) of about 7.9 mm. 
     A plurality of contacts  212  can be formed in each of contact regions  208   a  and  208   b  such that, when tab  204  is inserted into a corresponding receptacle connector, contacts  212  in regions  208   a  or  208   b  are electrically coupled to corresponding contacts in the receptacle connector. In some embodiments, contacts  212  are self-cleaning wiping contacts that, after initially coming into contact with a receptacle connector contact during a mating event, slide further past the receptacle connector contact with a wiping motion before reaching a final, desired contact position. 
     As an example, in one embodiment an ID module is embodied within an IC operatively coupled to the contacts of connector  200 . The ID module can be programmed with identification and configuration information about the connector and/or its associated accessory/adapter that can be communicated to a host device during a mating event. As another example, an authentication module programmed to perform an authentication routine, for example a public key encryption routine, with circuitry on the host device can be embodied within an IC operatively coupled to connector  200 . The ID module and authentication module can be embodied within the same IC or within different ICs. As still another example, a current regulator can be embodied within one of IC&#39;s  213   a  or  213   b . The current regulator can be operatively coupled to contacts that are able to deliver power to charge a battery in the portable electronic device and regulate current delivered over those contacts to ensure a constant current regardless of input voltage and even when the input voltage varies in a transitory manner. The function of the IC&#39;s is further described below in reference to  FIG. 4 . 
     Bonding pads  215  can also be formed within body  202  near the end of PCB  207 . Each bonding pad can be connected to a contact or contact pair within regions  208   a  and  208   b . Wires (not shown) can then be soldered to the bonding pads to provide an electrical connection from the contacts to circuitry within an accessory associated with connector  200 . In some embodiments, however, bonding pads are not necessary and instead all electrical connections between the contacts and components of connector  200  and other circuitry within an accessory are made through traces on a PCB that the circuitry is coupled to and/or by interconnects between multiple PCBs within the accessory. 
     The structure and shape of tab  204  is defined by a ground ring  205  that can be made from stainless steel or another hard conductive material. Connector  200  includes retention features  214   a ,  214   b  (not shown) formed as curved pockets in the sides of ground ring  205  that double as ground contacts. Body  202  is shown in  FIG. 2A  in transparent form (via dotted lines) so that certain components inside the body are visible. As shown, within body  202  is a printed circuit board (PCB)  207  that extends into ground ring  205  between contact regions  208   a  and  208   b  towards the distal tip of connector  200 . One or more integrated circuits (ICs), such as Application Specific Integrated Circuit (ASIC) chips  213   a  and  213   b , can be operatively coupled to PCB  207  to provide information regarding connector  200  and/or to perform specific functions, such as authentication, identification, contact configuration and current or power regulation. 
       FIG. 2B  illustrates a front view of plug connector  200 . The front view illustrates a cap  220 . Cap  220  can be made from a metal or other conductive material and can extend from the distal tip of connector  200  along the side of the connector towards body  202  either fully or partially surrounding contacts  212  formed in contact regions  208   a  and  208   b  in the X and Y directions. In some embodiments, cap  220  can be grounded in order to minimize interference that may otherwise occur on contacts  212  of connector  200  and can thus be referred to as a ground ring, e.g., ground ring  205  illustrated in  FIG. 2A . Contacts  212   (1) - 212   (N)  can be positioned within contact region  208   a  and additional contacts  214   (1) - 214   (N)  can be positioned within region  208   b  on the opposing surface of tab  204 . In some embodiments, N can be between 2 and 8. Contacts  212   (1)  . . .  212   (N)  and  214   (1)  . . .  214   (N)  can be used to carry a wide variety of signals including digital signals and analog signals as well as power and ground. 
       FIG. 2C  illustrates a cross-sectional schematic view of contacts  212 ,  214  and positioning of the contacts. Contacts  212 ,  214  can be mounted on either side of a PCB  250  as illustrated. In some embodiments, opposing contacts, e.g.,  212   (1)  and  214   (1)  may be shorted or electrically connected to each other through PCB  250 , e.g., using a via, to create an in-line connector design. In other embodiments, one contact from the top row of contacts  212  may be connected to at least one contact from the bottom row of contacts  214 . In still other embodiments, all contacts may be independent with no connections between any of the contacts or the contacts may have other connections schemes between them. In the instance where each contact is independent and not connected to any other contact, a different receptacle connector may be used. Contacts  212 ,  214  can be made from a copper, nickel, brass, a metal alloy or any other appropriate conductive material. Spacing is consistent between each of the contacts on the front and back sides and between the contacts and the edges of the connector providing 180 degree symmetry so that plug connector  200  can be inserted into a corresponding receptacle connector in either of two orientations. 
     When connector  200  is properly engaged with a receptacle connector, each of contacts  212   (1) - 212   (N)  or  214   (1) - 214   (N)  may be in electrical connection with a corresponding contact of the receptacle connector.  FIG. 2D  illustrates a pin-out configuration for connector  200  according one particular embodiment of the present invention as described in connection with  FIG. 2C  above. 
     The pin-out shown in  FIG. 2D  includes four contacts  212   (4) ,  212   (5) ,  214   (4) , and  214   (5)  that are electrically coupled together to function as a single contact dedicated to carrying power to a connected host device. Connector  200  may also include accessory ID contacts  212   (8)  and  214   (8) ; accessory power contacts  212   (1)  and  214   (1) ; and eight data contacts arranged in four pairs. The four pairs of data contacts may be (a)  212   (2)  and  212   (3) , (b)  212   (6)  and  212   (7) , (c)  214   (2)  and  214   (3) , and (d)  214   (6)  and  214   (7) . Host power contacts  212   (4) ,  212   (5) ,  214   (4) , and  214   (5)  carry power from an accessory associated with connector  200  to a portable electronic device that is coupled to the accessory via connector  200 . The host power contacts can be sized to handle any reasonable power requirement for an electronic device or host device, and for example, can be designed to carry between 3-20 Volts from an accessory to charge the portable electronic device connected to connector  200 . In this embodiment, host power contacts  212   (4) ,  212   (5) ,  214   (4) , and  214   (5)  are positioned in the center of contact regions  208   a ,  208   b  to improve signal integrity by keeping power as far away as possible from the sides of ground ring  205 . 
     Accessory power contacts  212   (1)  and  214   (1)  can be used for an accessory power signal that provides power from the electronic device (i.e. the host device) to an accessory. The accessory power signal is typically a lower voltage signal than the host power in signal received over host power contacts  212   (4)  and  212   (5) , for example, 3.3 volts as compared to 5 volts or higher. The accessory ID contacts provide a communication channel that enables the host device to authenticate the accessory and enable the accessory to communicate information to the host device about the accessory&#39;s capabilities as described in more detail below. 
     The four pairs of data contacts (a)  212   (2)  and  212   (3) , (b)  212   (6)  and  212   (7) , (c)  214   (2)  and  214   (3) , and (d)  214   (6)  and  214   (7)  may be used to enable communication between the host and accessory using one or more of several different communication protocols. For example, data contacts  212   (2)  and  212   (3)  are positioned adjacent to and on one side of the power contacts, while data contacts  212   (6)  and  212   (7)  are positioned adjacent to but on the other side of the power contacts. A similar arrangement of contacts can be seen for contacts  214  on the other surface of the PCB. The accessory power and accessory ID contacts are positioned at each end of the connector. The data contacts can be high speed data contacts that operate at rate that is two or three orders of magnitude faster than any signals sent over the accessory ID contact which makes the accessory ID signal look essentially like a DC signal to the high speed data lines. Thus, positioning the data contacts between the power contacts and the ID contact improves signal integrity by sandwiching the data contacts between contacts designated for DC signals or essentially DC signals. 
       FIG. 2E  illustrates a pin-out configuration for a connector  200  according another particular embodiment of the present invention. 
     Connector  200  is a reversible connector. In other words, based on the orientation in which connector  200  is mated with a corresponding connector of a host device, either the contacts on the surface  208   a  or  208   b  are in physical and electrical contact with the contacts in the corresponding connector of the host device. As illustrated in  FIG. 2E , connector  200  may have eight contacts arranged on an upper surface of a PCB  250  and eight contacts arranged on a lower surface of PCB  250 . 
     Connector  200  includes two contacts  212   (1)  and  214   (4)  that can function as accessory ID contacts to carry the identification signals between the accessory and the portable electronic device. Contacts  212   (1)  and  214   (4)  are electrically connected to each other as illustrated in  FIG. 2E . Connector  200  can have four pairs of data contacts, (a)  212   (2)  and  212   (3) , (b)  212   (6)  and  212   (7) , (c)  214   (2)  and  214   (3) , and (d)  214   (6)  and  214   (7) . In this particular embodiment, opposing data contacts, e.g.,  212   (2)  and  214   (2) , are electrically connected to each other via PCB  250  as illustrated in  FIG. 2E . Connector  200  may further include host power contacts  212   (4)  or  214   (5)  that may be electrically connected to each other. Host power contacts  212   (4)  or  214   (5)  can carry power to the host device that is mated with connector  200 . For example, plug connector  200  may be part of a power supply system designed to provide power to the host device. In this instance, either contact  212   (4)  or  214   (5)  may carry power from the power supply to the host device, e.g., to charge a battery in the host device. 
     Connector  200  may further include accessory power contacts  212   (5)  and  214   (8)  that may be electrically connected to each other, e.g., via PCB  250 . Accessory power contacts carry power from the host device to a connected accessory. For example, in some instances, an accessory connected to the host device may not be self-powered and may derive its power from the host device. In this instance, the host device can supply power to the accessory over either of the accessory contacts, depending on the orientation of connector  200  with respect to a corresponding connector of the host device. Connector  200  may further include two ground contacts  212   (8)  and  214   (1)  electrically connected to each other. The ground contacts provide a ground path for connector  200 . 
       FIG. 3A  illustrates a receptacle connector  300  according to an embodiment of the present invention. Receptacle connector  300  includes a housing  302  that defines a cavity  304  and houses N contacts  306   (1) - 306   (N)  within the cavity. In operation, a connector plug, such as plug connector  200  can be inserted into cavity  304  to electrically couple the contacts  212   (1) - 212   (N)  or  214   (1) - 214   (N)  to respective contacts  306   (1) - 306   (N) . Each of the receptacle connector contacts  306   (1) - 306   (N)  electrically connects its respective plug contact to circuitry associated with the electrical/host device in which receptacle connector  300  is housed. For example, receptacle connector  300  can be part of host device  102  and electronic circuitry associated with the host device is electrically connected to receptacle  300  by soldering tips of contacts  306   (1) - 306   (N)  that extend outside housing  302  to a multilayer board such as a printed circuit board (PCB) within the portable media device. Note that connector  300  includes contacts on just a single side so it can be made thinner. In other embodiments, connector  300  may have contacts on each side. 
       FIG. 3B  illustrates a cross section view of receptacle connector  300  according to an embodiment of the present invention. As illustrated, in some embodiments, Additional contacts  308   (1)  and  308   (2)  are located at either ends of contacts  306   (1) - 306   (N) . Contacts  308   (1)  and  308   (2)  may be used to detect whether the plug connector is fully inserted into cavity  304  or inserted to a point where contacts  212  (or  214 ) of plug connector  200  are physically coupled to contacts  306  of receptacle connector  300 . In some embodiments, contacts  308   (1)  and  308   (2)  can also be used to detect whether the plug connector has been disconnected from the receptacle connector. In some embodiments, contacts  308  can make contact with cap  220  of plug connector  200  when the plug connector is inserted beyond a certain distance within cavity  304 . In some embodiments, contacts  308  are placed such that they will make contact with the ground ring of plug connector only when contacts  212  make a solid physical connection with contacts  306 . In some embodiments, when contacts  308  connect to the ground ring of the plug connector, a signal may be generated indicating the connection. 
     In some embodiments, the receptacle connector  300  may have contacts  306   (1)-(N)  only on a single side inside cavity  304  as described above. In a particular embodiment, receptacle connector  300  may have eight (8) contacts  306   (1) - 306   (8) . Some or all of these contacts may be configured to perform one of several functions depending on the signals available on a plug connector. Plug connector  200  may be associated any one of several accessories that may be designed to work with a host device that is associated with receptacle connector  300 . For example, plug connector  200  may be associated with an audio only accessory in which case the signals available on the contacts, e.g.,  206   (1) - 206   (N) , of the plug connector may include audio and related signals. In other instances, where plug connector  200  is associated with a more complex accessory such as video accessory, the contacts of plug connector may carry audio, video, and related signals. Thus, in order to enable receptacle connector  300  to be operable with various different types of signal, contacts  306   (1)-(8)  of receptacle connector  300  can be made configurable based on the signals available from a plug connector  200 . 
     In the particular embodiment, receptacle connector  300  has eight contacts  306   (1)-(8)  in addition to two connection detection contacts  308   (1)  and  308   (2) . The operation of the connection detection contacts  308   (1)  and  208   (2)  is described above in relation to  FIG. 3B . Some or all of contacts  306   (1) - 306   (8)  may have an associated switch that can configure the contact to carry one of many possible signals. It is to be noted that some other contacts from among contacts  306   (1) - 306   (8)  may each have a similar switch coupled to it. The switch can be used to configure its associated contact to carry any one of signals S 1 -S n  depending on the configuration of the plug connector. 
     In a particular embodiment, contact  306   (1)  may be an identification bus pin (ACC_ID) and can be configured to communicate a command operable to cause an accessory to perform a function and provide a response to a host device unique to the command. The command may be any one or more of a variety of commands, including a request to identify a connector pin and select one of a plurality of communication protocols for communicating over the identified connector pin, a request to set a state of the accessory, and a request to get a state of the accessory. Contact  306   (1)  may also or alternatively be configured to communicate power from the host device to the accessory (e.g., ACC_PWR). For example, contact  306   (1)  may be coupled to a positive (or negative) voltage source within the host device so as to generate a voltage differential with another contact (such as a ground contact which may be, e.g., contact  306   (8) ). 
     In a particular embodiment, contacts  306   (2)  and  306   (3)  may form a first pair of data contact (DP 1 /DN 1 ). The data contacts may be configured to carry one or more of a variety of signals, such as (a) USB differential data signals, (b) non-USB differential data signal, (c) UART transmit signal, (d) UART receive signal, (e) digital debug input/output signals, (f) a debug clock signal, (g) audio signals, (h) video signals, etc. 
     In a particular embodiment, contact  306   (4)  may carry incoming power (e.g., a positive voltage relative to another contact such as a ground pin) to the host device (e.g., from a power source in or coupled to the accessory) with which receptacle connector  200  is associated. Contact  306   (5)  may also function as an identification bus pin (ACC_ID) similar to contact  306   (1)  described above. Contact  306   (5)  may also or alternatively be configured to communicate power from the host device to the accessory (e.g., ACC_PWR), depending on the orientation of a connected plug connector  200  (or connector  200 ) with respect to receptacle connector  300 . 
     In a particular embodiment, contacts  306   (6)  and  306   (7)  may form a second pair of data pins (DP 2 /DN 2 ) and can each be configured to carry one or more of a variety of signals, such as (a) USB differential data signals, (b) non-USB differential data signal, (c) UART transmit signal, (d) UART receive signal, (e) digital debug input/output signals, (f) a debug clock signal, (g) audio signals, (h) video signals, etc. 
     In a particular embodiment, contact  306   (8)  may be a ground pin or otherwise provided at a voltage potential lower than contacts  306   (1) ,  306   (4) , and  306   (5)  so as to provide a voltage potential for power being provided to or from the host device. 
     In some embodiments, tab  204  has a 180 degree symmetrical, double orientation design which enables plug connector  200  (or connector  200 ) to be inserted into receptacle  300  in both a first orientation and a second orientation. 
       FIGS. 3C and 3D  illustrate pin-out configuration for a receptacle connector according to two different embodiments of the present invention. In one embodiment, receptacle connector  300  has a pin-out as shown in  FIG. 3C  that matches pin-out of connector  200  in  FIG. 1D  and in another embodiment receptacle connector  300  has a pin-out as shown in  FIG. 3D  that matches pin-out of connector  200  of  FIG. 1E . In each of  FIGS. 3C and 3D , the ACC 1  and ACC 2  pins are configured to mate with either the accessory power (ACC_PWR) or accessory ID (ACC_ID) pins of the plug connector depending on the insertion orientation of plug connector, the pair of Data A contacts is configured to mate with either the pair of Data  1  contacts or the pair of Data  2  contacts of the plug connector, and the P_IN (power in) pin or pins are configured to mate with the Host Power contact or contacts of the plug connector. Additionally, in the pin-out of  FIG. 3D , the GND contact is configured to mate with the GND contact in the plug connector. 
       FIG. 4  illustrates connection of an accessory  420  (e.g., implementing accessory  104  of  FIG. 1 ) to a host device  410  (e.g., implementing host device  102  of  FIG. 1 ) according to an embodiment of the present invention. In this embodiment a connector  422  (e.g., implementing plug connector  200  of  FIG. 2A ) of accessory  420  can be physically mated with connector  412  (e.g., implementing receptacle connector  300  of  FIG. 3A ) of host device  410 . Both connectors  422  and  412  may have additional pins as described above. When connector  422  is physically mated with connector  412 , the corresponding contacts of the two connectors are also physically connected with each other. For example, as shown in  FIG. 4 , contact  423  of connector  422  is physically connected to contact  413  of connector  412  and contact  424  of connector  422  is connected to contact  414  of connector  412 . It is to be noted that only two contacts are shown in  FIG. 4  for ease of explanation. One skilled in the art will realize that other contacts in the two connectors may also be physically connected to each other. 
     At accessory  420 , power limiting circuitry  421  may monitor pin  424  for incoming power and/or requests. For example, in one embodiment, power may be communicated from host device  410  to accessory  420  via pin  424  (e.g., ACC_PWR contact described above). This power may be used for accessory  420  to operate in the event accessory  420  cannot acquire operating power from other sources such as power source  430  or does not have an internal power source. If power is not received, then power limiting circuitry  421  may continue to monitor pin  424 . However, if power is received from host device  410 , then power limiting circuitry  421  may disable a power path between power source  430  and host device  410 . In some cases, the power path may be disabled by default, and thus further disabling may be omitted. Once the power path is disabled, power limiting circuitry  421  may receive and read the request for an accessory identifier. If the request is valid, then power limiting circuitry  421  may send an accessory identifier to host device  410 , and enable (or re-enable) the power path between power source  430  and host device  410 . Otherwise, power limiting circuitry  421  may continue to monitor pin  424 . 
     In the instance that accessory  420  provides power to host device  410 , once a connection has been established between host device  410  and accessory  420 , the power path between power source  430  and host device  410  may be enabled. In some embodiments, this may allow host device  410  to acquire operating power from accessory  420 , such as when the host device  410  does not have sufficient power to operate a main processor to execute software provided in the host device  410  (e.g., it has a dead battery). In other embodiments, host device  410  may have sufficient power to operate such software, in which case it may choose to continue operating using its own power or begin to operate using power supplied via the newly enabled power path. 
     In some embodiments, power limiting circuitry  421  may comprise a number of different circuits operable to perform different functions. For example,  FIG. 5  illustrates a high level block diagram of power limiting circuitry  421  according to an embodiment of the present invention. In accordance with an embodiment, power limiting circuitry  421  includes impedance altering circuitry  421   a  and identification circuitry  421   b . Impedance altering circuitry  421   a  may be disposed in the power path between power source  430  and host device  410 , whereas identification circuitry  421   b  may be disposed between impedance altering circuitry  421   a  and pin/contact  424 . 
     Identification circuitry  421   b , which may be implemented as single integrated circuit (IC) chip, may be operable to receive data from host device  410  via pin  424  and respond to the received data. For example, identification circuitry  421   b  may have stored therein an accessory identifier, and may be operable to communicate the accessory identifier to host device  410  in response to receiving a request for the accessory identifier. Identification circuitry  421   b  may also be operable to send instructions to impedance altering circuitry  421   a  instructing impedance altering circuitry  421   a  to alter an impedance of the power path between power source  430  and host device  410 . 
     Impedance altering circuitry  421   a , which may be implemented as a single IC chip or together with identification circuitry  421   b  as a single IC chip, may be operable to alter an impedance of the power path between power source  430  and host device  410 . The altering of the impedance may be in response to an instruction from identification circuitry  421   b  or, in some embodiments, in response to an instruction sent directly from host device  410 . There are various ways that impedance altering circuitry  421   a  may alter the impedance of the power path, as further described herein. 
       FIG. 6  is a schematic of impedance altering circuitry  421   a  according to one embodiment of the present invention. Impedance altering circuitry  421   a  according to this embodiment includes a resistive element  425  coupled in parallel with a switch  426  where both are arranged in a power path between points A and B. Resistive element  425  may provide any suitable resistance for measurably altering an impedance characteristic of power limiting circuitry  421   a . For example, resistive element  425  may have a resistance of 1 Ohm, 2 Ohm&#39;s, 3 Ohm&#39;s, 100 Ohm&#39;s, 200 Ohm&#39;s, 300 Ohm&#39;s, 1 kOhm, 2 kOhm&#39;s, 3 kOhm&#39;s, 1 MOhm, 2 MOhm&#39;s, 3 MOhm&#39;s, be in a range from 1 to 3 Ohm&#39;s, 100 Ohm&#39;s to 300 Ohm&#39;s, 1 kOhm to 3 kOhm, 1 MOhm to 3 MOhm&#39;s, or less than 1 Ohm or greater than 3 MOhm&#39;s. Resistive element  425  includes a first end  5  that may be coupled to power source  430 , and a second end  6  that may be coupled to power pin  423  of connector  422 , such that resistive element  425  is disposed in a power path between power source  430  and host device  410 . In some embodiments, resistive element  425  may be implemented as a current limited source or Low-Dropout regulator (LDO) type device or circuitry. 
     Switch  426  may be any suitable switching element that allows current provided from power source  430  to selectively bypass resistive element  425 . For example, switch  426  may be a MOSFET, JFET, or other type of transistor or other semiconductor device operable to switch electronic signals and power. Switch  426  is coupled in parallel to resistive element  425  and includes a first terminal  7  (e.g., a source) coupled to first end  5  of resistive element  425 , a second terminal  8  (e.g., a drain) coupled to second end  6  of resistive element  425 , and a third terminal  9  (e.g., a gate) for controlling the operation of switch  426 . In some embodiments, first terminal  7  is coupled to power source  430 , second terminal  8  is coupled to power pin  423 , and third terminal  9  is coupled to pin  424  of connector  122 . Switch  426 , when in an OFF state, has a resistance significantly higher than the resistance of resistive element  425 . When switch  426  is in an ON state, it has a resistance that is significantly lower than the resistance of resistive element  425 . 
     As described above, power limiting circuitry  421  may operate to alter an impedance of a power path between power source  430  and host device  410 . In some embodiments, power limiting circuitry  421  may operate in different modes, such as in a bypass mode and a power limiting mode. Such modes may be enabled/disabled in response to instructions from host device  410  and, in some embodiments; power limiting circuitry  421  may operate in some modes (e.g., the power limiting mode) by default. Operating by default in power limiting mode may advantageously reduce user risk to exposed voltage potentials, such as when connector  422  of accessory  420  is not connected to connector  412  of host device  410 . For example, when the accessory is first connected to the host device, the accessory may enable the power limiting mode in which switch  426  is turned OFF thereby routing the power from power source  430  via resistive element  425 . Depending on the value of resistive element  425  and output voltage of power source  430 , a fixed output current is available at point A. This current is usually very low, e.g., 15 mA. Thus initially only this small current is available to the host device. Once the host device confirms that the accessory is authentic, the accessory may turn ON switch  426  (bypass mode) resulting in the power being routed via switch  426 . In this instance, a higher current is now available at point A since switch  426  presents very little resistance to the incoming voltage. In the instance where the host device is unable to confirm the authenticity of the accessory, the bypass mode is not enabled and the host device cannot receive power from the accessory. 
     In instances where the host device has enough power, when the accessory connector is mated with the host device connecter, the host device detects connection of the accessory device via the connection detection contacts described in reference to  FIG. 3B  above and initiates communication with accessory to authenticate the accessory and subsequently to receive power from the accessory. 
     However in instances when the host device has no power, e.g., the host device has a dead battery, the host device may be unable to detect connection of an accessory and thus unable to initiate communication with the accessory in order to receive power from the accessory. In this instance, it may be helpful to have a mechanism within the accessory to detect connection with a host device so that the accessory can provide enough power to the host device to initialize the controller/circuitry in the host device. Using this minimal power, the host device can then initiate communication with the accessory and thus be able to receive power from the accessory, as described above. In another instance when the accessory is a power supply, it would be desirable to only output minimal power, e.g., on the P_IN contact of the plug connector described above, in order to prevent dendrite growth and also to prevent arcing/damage to the plug connector if the contacts of the plug connector are accidently grounded or shorted. Once the accessory detects that there is a host device connected to the plug connector then it would be safe to output the normal power on its contacts. 
       FIG. 7  illustrates circuitry that enables an accessory to detect presence of a host device when the host device has no power, according to an embodiment of the present invention. 
     The accessory may include a constant current source  702 . In some embodiments, current source  702  may provide between 10 μA and 1 mA of current. Current source  702  is disposed in the power path between the accessory and the host device. For example, current source may be connected to the P_IN contact of the accessory connector, e.g., plug connector  100  of  FIG. 1 . On the host side, the host device may include switch  708  connected in parallel to a diode device  704 . These two components represent the resistive element within the host device. A capacitor  706  connected to the resistive element completes an RC circuit within the host device. In some embodiments, capacitor  706  may have a value of between 10 nF and 10 μF. Consider an instance where the accessory is a power supply. When the accessory is connected to a power source (e.g., a wall outlet), a conventional accessory will output the full voltage that the accessory is programmed to output. For example, if the conventional power supply is programmed to output 5V DC, then as soon as the conventional power supply is connected to a power source it will output the 5V via its connector regardless of whether a host device is connected to it or not. 
     The accessory as illustrated in  FIG. 7  will not automatically output the full programmed voltage. Instead, the accessory according to the embodiment of the present invention outputs a certain voltage (e.g., between 3V and 5V) over the P_IN contact of its connector at a very low current value until detects a host device connection. This mode of operation of the accessory where the accessory outputs a very low current is referred to herein as the “connection detection mode” for ease of explanation. In some embodiments, the connection detection mode may be the default mode for the accessory. In some embodiments, the voltage/current is outputted over the P_IN contact in a pulsed manner instead of in a constant manner. For example, the accessory may output a voltage/current pulse with a duty cycle of between 0.1% and 1% and having a pulse width/duration of between 0.01 seconds and 0.001 seconds. In some embodiments, the frequency associated with the duty cycle can range between 100 Hz and 1000 Hz. This reduces and/or eliminates the possibility of dendrite growth over the contacts of the accessory connector since current/voltage is only present for a short period on the contact. 
     The accessory monitors the voltage at the P_IN contact after outputting the voltage/current pulse over the P_IN contact to determine whether a host device is connected. A comparator  710  is connected to the P_IN contact and receives a reference voltage V th  as its other input. The output of comparator  710  is coupled to an OR gate  712 , which receives the accessory identifier as its other input. The output of OR gate  712  is the power limiting mode described above in connection with  FIGS. 5 and 6 . 
     Consider that a host device is connected to the accessory. In this instance, when the accessory provides the current (in the connection detection mode) supplied by current source  702 , the host-side circuitry (e.g., capacitor  706 , diode  704  and switch  708 ) presents a certain capacitance and as a result the voltage at the P_IN contact begins to rise. If the measured voltage at the P_IN contact reaches the reference voltage V th  at or after a certain time T 1 , the accessory can conclude that a host device is connected to it. Based on the design of the accessory and/or the host device a suitable value for V th  and T 1  can be programmed. In a particular embodiment, the value of V th  may be between 0 volts and 1.8 volts and the value of T 1  can be between 1 microsecond and 100 microseconds.  FIG. 8  illustrates the relationship between voltage measured at the P_IN contact and the time taken by the voltage to reach a certain value/level. As illustrated in  FIG. 8 , at point P, the voltage at the P_IN contact has reached the reference voltage V th  in time T 1 . In this disclosure, we will specify this relationship between voltage and time as indicating presence of a host device. If the measured voltage reaches the value of V th  at any time before T 1  then the accessory concludes that no host is connected to the host device. If the measured voltage reaches the value of V th  at or after time T 1 , then the accessory concludes that a host device is connected to the accessory. 
     In the instance when the host device is not connected to the accessory, as soon as the current is provided over the P_IN contact, the voltage at the P_IN contact will rise to the output voltage specified for the connection detection mode (e.g., 3-5V as described above) before expiration of time T 1  since there is no capacitance presented at the P_IN contact. When the accessory detects that the voltage measure at the P_IN contact meets or exceeds V th  prior to T 1  the accessory concludes that there is no host device connected it. The accessory then terminates the current/voltage output on the P_IN contact and continues operating in the connection detection mode in which it provides the detection current in a pulsed manner as described above. 
     If the accessory detects connection of a host device. In other words, if the measured voltage at the P_IN contact reaches V th  at or after time T 1 , the accessory can enable the power limiting mode and provide the necessary power to the host device to enable initiation of communication with the accessory. The host device can then authenticate the accessory and subsequently the accessory can enable the bypass mode to provide appropriate power to the host device for operation or for charging a battery of the host device. 
       FIG. 9  illustrates the pulsed voltage output in a connection detection mode according to an embodiment of the present invention. As illustrated in  FIG. 9 , if the measured voltage V equals to or exceeds V th  in time t that is less than T 1 , then the accessory can conclude that no host is connected. Whereas if the measured voltage V equals V th  at or after T 1 , then the accessory can conclude that a host device is connected to the accessory. 
     As described above, the connection detection current source  702  is disposed along the power path between the accessory and the host device. In some embodiments, current source can be connected in parallel to the impedance altering circuitry described in  FIG. 6  above. Thus, in this embodiment, there are three power paths between the power source and the host device, via the accessory.  FIG. 10  is a schematic that illustrates an impedance altering circuitry  431   a  according to another embodiment of the present invention. The difference between the embodiment of  FIG. 6  and this embodiment is the addition of current source  702  in parallel with resistive element  425  and switch  426 . In this embodiment, when the accessory is not connected to a host device the accessory operates in the connection detection mode in which the power path via current source  702  is enabled. When the accessory detects a host device, which has no power, connected to it (e.g., using the techniques described above), the accessory enables the power limiting mode and the power path via resistive element  425  is enabled. Once the accessory is authenticated by the host device, the accessory operates in the bypass mode and the power path via switch  426  is enabled. 
       FIG. 11  is a flow diagram of a process  1100  for detecting connection of a host device to an accessory device according to an embodiment of the present invention. Process  1100  may be performed, e.g., by accessory  104  of  FIG. 1 . 
     At step  1102  the accessory outputs a pulsed current over a power contact of an accessory-side connector. At step  1104  the accessory measures a voltage at the power output contact of the accessory-side connector. At step  1106  the accessory determines whether the measured voltage V is equal to greater than a reference voltage V th  and whether the time taken by the voltage to reach V th  is equal to or greater than a pre-determined time. If the accessory determines (step  1108 ) that the measured voltage reaches or exceeds V th  within a time less than the pre-determined time, the accessory concludes that a host device is not connected to the accessory (step  1110 ) and process  1100  returns to step  1102 . 
     However, if the accessory determines (step  1112 ) that the measure voltage V reached V th  at or after the pre-determined time, then the accessory concludes that a host device is connected to the accessory (step  1114 ) and the process ends. 
     It should be appreciated that the specific steps illustrated in  FIG. 11  provide a particular method of detecting connection of a host device according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in  FIG. 11  may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. 
       FIG. 12  is a flow diagram of a process  1200  for operating an accessory according to an embodiment of the present invention. Process  1200  may be performed, e.g., by accessory  104  of  FIG. 1 . 
     Initially the accessory may enable a connection detection mode (step  1202 ) in which the accessory outputs a current/voltage in a pulsed manner over a power contact of an accessory-side connector. Subsequent to outputting the voltage/current pulse, the accessory measures the voltage at the power contact (step  1204 ). If the measured voltage becomes equal to or exceeds a predetermined threshold voltage prior to expiration of a predetermined time (step  1206 ), the accessory concludes that there is no host device connected to it (step  1208 ). Thereafter the process returns to step  1202  where the accessory outputs the pulsed voltage/current based having a programmable duty cycle. If the measured voltage reaches the predetermined voltage value at or after expiration of the predetermined time (step  1210 ), the accessory concludes that a host device is connected to it (step  1212 ). Based on this conclusion, the accessory disables the connection detection mode (step  1214 ) and enables a power limiting mode in which the accessory supplies a higher constant current and voltage over the power contact (step  1216 ). This current/voltage is enough for the host device to start communicating with the accessory. Thereafter the accessory communicates with the host device to authentication the accessory (step  1218 ). Once the accessory is authenticated, the accessory disables the power limiting mode (step  1220 ) and enables a bypass mode (step  1222 ) in which the accessory provides the power needed for normal operation/charging of the host device. 
     It should be appreciated that the specific steps illustrated in  FIG. 12  provide a particular method of operating an accessory according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in  FIG. 12  may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. 
     Circuits, logic modules, processors, and/or other components can be described herein as being “configured” to perform various operations. Those skilled in the art will recognize that, depending on implementation, such configuration can be accomplished through design, setup, interconnection, and/or programming of the particular components and that, again depending on implementation, a configured component might or might not be reconfigurable for a different operation. For example, a programmable processor can be configured by providing suitable executable code; a dedicated logic circuit can be configured by suitably connecting logic gates and other circuit elements; and so on. 
     While the embodiments described above can make reference to specific hardware and software components, those skilled in the art will appreciate that different combinations of hardware and/or software components can also be used and that particular operations described as being implemented in hardware might also be implemented in software or vice versa. 
     Computer programs incorporating various features of the present invention can be encoded on various non-transitory computer readable storage media; suitable media include magnetic disk or tape, optical storage media, such as compact disk (CD) or DVD (digital versatile disk), flash memory, and the like. Computer readable storage media encoded with the program code can be packaged with a compatible device or provided separately from other devices. In addition program code can be encoded and transmitted via wired optical, and/or wireless networks conforming to a variety of protocols, including the Internet, thereby allowing distribution, e.g., via Internet download. 
     Thus, although the invention has been described with respect to specific embodiments, it will be appreciated that the invention is intended to cover all modifications and equivalents within the scope of the following claims.

Metadata:
Filing Date: 20130207
Publication Date: 20141125
Grant Date: 20141125
Priority Date: 20130207
Inventors: MINOO JAHAN
RICH ZACHARY
Assignee: APPLE INC
CPC Classifications: [{"code": "H04M1/72409", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04M1/72412", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04M1/72527", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F11/3051", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1632", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/72409", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/266", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/28", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F11/3051", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F1/1632", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04M1/72412", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50116184