Abstract:
A small form-factor, high performance connector is disclosed. This connector is intended for use with high bandwidth digital video, implementing differential digital signaling, as well as for high bandwidth analog video. The described connector system performs the function of the Digital Visual Interface (DVI) connector, but in a significantly smaller package. Signal integrity is maintained in the smaller form factor by the expedient assignment of signals to pins so that the pin above or below any signal is not used on that interface, thus reducing the chances for signal crosstalk. The pin shape and spacing are created to match pin lengths and minimize inductance while maintaining the proper impedance up to 2.5 GHz. This connector system also implements a tactile feedback mechanism to aid with cable plug insertion, and incorporates a keying mechanism to prevent reverse-plugging.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application No. 61/019,278, filed Jan. 6, 2008, titled “MICRODVI CONNECTOR,” which is incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Many electronic devices connect to each other using cables typically made up of a number of wires connected to pins located in connectors at each end of the cable. These connectors then mate with connectors in the electronic devices. These connectors may be based on a standard, that is, the connector may have an agreed-to size and pin location, or they may be proprietary. 
         [0003]    Other connectors may be a hybrid of these, that is, the pin functions may be standardized, but the pin locations and connector form factor may be proprietary. Such a connector may be used on one end of a cable while a standard connector is used on the other. This arrangement has the advantage of allowing devices to use a proprietary connector to connect to a standardized device. 
         [0004]    In some applications it is desirable to reduce the size of these connectors. For example, a low height, or smaller z direction, allows a connector to be used on a thinner device. A narrower connector, a shorter x direction, allows more connectors to be included along an edge of a device. 
         [0005]    Unfortunately, smaller connectors require pin spacing to be reduced. Reduced spacing results in a higher level of signal crosstalk and interaction. This in turn diminishes signal integrity and hampers device performance. 
         [0006]    Smaller connectors may also create an undesirable user experience. That is, it may be hard for users to know when they have properly inserted the cable connector into the device connector. It may be hard for users to know if they have inserted the connector in the correct direction and whether they have fully inserted the connector. 
         [0007]    Thus, what is needed are connectors having a reduced size, a high level of signal integrity, and provide a tactile feedback to users such that they can determine whether a connection has been properly made. 
       SUMMARY 
       [0008]    Accordingly, embodiments of the present invention provide connectors having a smaller profile. The profile, or form factor, may be smaller in either or both height, or z direction, and width, or x direction. While these connectors are particularly useful as a smaller (Digital Visual Interface) DVI connector, referred to herein as a MicroDVI connector, the concepts described herein may be used with other types of connectors. 
         [0009]    Various embodiments of the present invention provide an enhanced user experience by providing keys that prevent the cable from being inserted in the wrong direction. These keys are arranged in such a way as to prevent the pins of the connector from being damaged when the connector is improperly inserted, that is, when it is inserted upside down. 
         [0010]    In another exemplary embodiment of the present invention, the user experience is also enhanced by the use of one or more fingers. As the connector is inserted, the finger provides resistance that builds until the connector is inserted a certain distance, after which the resistance releases, letting the user know the connection has been made. These or other fingers may also be used to provide a tight mechanical connection. 
         [0011]    In various embodiments of the present invention, signal integrity is maintained in the smaller form factor connector by using a number of techniques. For example, in the connector, analog pins are located on one side of a board, while digital pins are located on the other. Spacing between pins is arranged to provide necessary impedances over frequency. Differential lines are located near each other and their trace lengths and routing are matched. 
         [0012]    An exemplary embodiment of the present invention provides a connector receptacle to receive a connector insert. This connector receptacle includes a first key formed on a wall of the connector receptacle, the key formed to fit with a narrow portion of the connector insert, and a finger formed on the wall of the connector receptacle. The finger is formed to provide resistance as the connector insert is initially inserted in the connector receptacle, and to release the resistance once the connector insert has been inserted into the connector receptacle a certain distance. 
         [0013]    Another exemplary embodiment of the present invention provides a connector insert to be inserted into a connector receptacle. This connector insert includes an insert portion having a wider portion and a narrower portion, the narrower portion to fit into the connector receptacle having a key formed on an inner wall of the connector receptacle, and a top surface to meet a finger formed on the inner wall of the connector receptacle, the finger formed to provide resistance as the connector insert is initially inserted in the connector receptacle, and to release the resistance once the connector insert has been inserted into the connector receptacle a certain distance. 
         [0014]    Yet another exemplary embodiment of the present invention provides a connector comprising a connector receptacle and a connector insert. This connector includes a connector receptacle having a first key formed on an inner wall of the connector receptacle, and a finger formed on the inner wall of the connector receptacle, and a connector insert having an insert portion having a wider portion and a narrower portion, the narrower portion to fit into the connector receptacle where the key is formed, and a top surface to meet the finger, the finger formed to provide resistance as the connector insert is initially inserted in the connector receptacle, and to release the resistance once the connector insert has been inserted into the connector receptacle a certain distance. 
         [0015]    Various embodiments of the present invention may incorporate one or more of these and the other features described herein. A better understanding of the nature and advantages of the present invention may be gained by reference to the following detailed description and the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  illustrates an electronic system utilizing a connector including a connector receptacle and connector insert according to an embodiment of the present invention; 
           [0017]      FIG. 2  illustrates a connector receptacle and connector insert according to an embodiment of the present invention; 
           [0018]      FIG. 3  illustrates two keys in a connector receptacle according to an embodiment of the present invention; 
           [0019]      FIG. 4  illustrates top, side, and front views of a finger on a connector receptacle according to an embodiment of the present invention; 
           [0020]      FIG. 5  illustrates the deformation of a finger as a connector insert is inserted into a connector receptacle according to an embodiment of the present invention; 
           [0021]      FIG. 6  illustrates a board located in a connector receptacle according to an embodiment of the present invention; 
           [0022]      FIG. 7  illustrates a specific pinout employed by a connector receptacle according to an embodiment of the present invention; 
           [0023]      FIGS. 8A-8B  illustrate through-hole and surface-mount pins according to an embodiment of the present invention; 
           [0024]      FIG. 9  illustrates a method of routing a pair of differential signals in a connector according to an embodiment of the present invention; and 
           [0025]      FIGS. 10-14  are mechanical diagrams of a connector receptacle according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0026]      FIG. 1  illustrates an electronic system utilizing a connector including a connector receptacle and connector insert according to an embodiment of the present invention. This figure includes a laptop computer  100  that has a proprietary MicroDVI connector that is capable of driving a second monitor. This figure, as with the other included figures, is shown for illustrative purposes only and do not limit either the possible embodiments of the present invention or the claims. 
         [0027]    In this example, the laptop  100  includes a connector receptacle  110  according to an embodiment of the present invention. This connector receptacle  110  may be located on other types of electronic devices, for example, portable media devices, cameras, set-top boxes, computers, and others. The use of a connector receptacle  110  having a lower height, or shorter z direction, on the laptop allows the laptop to be thinner, and therefore more easily transported. When the connector receptacle  110  is narrower, or shorter in the x direction, more connectors may be placed on the side of the laptop  100 . 
         [0028]    A cable, or in this case a dongle  120 , connects to the connector receptacle  110  using a connector insert  130 . A connector insert housing  140  is provided to allow electrical connections to be made between wires in the cable  120  and pins located in the connector insert  130 . The connector housing  140  also provides something for a user to hold while inserting the connector insert  130  into the connector receptacle  110 . 
         [0029]    The other end of the cable or dongle  140  may be a standard or proprietary connection. For example, where the connector receptacle  110  provides pins for a Digital Visual Interface, the second end of the cable  140  may be a standard Video Graphics Array (VGA) or DVI connector. This connector may be used to make a connection to the monitor. 
         [0030]    While embodiments for of the present invention are particularly well suited to provide a reduced size DVI connector receptacle and connector insert, other embodiments of the present invention may be employed for other types of connections. Also, in the future, other types of interfaces will be developed, and these connector receptacles and connector inserts will be useful for those as well. 
         [0031]      FIG. 2  illustrates a front view of a connector receptacle  200  and connector insert  215  according to an embodiment of the present invention. When used as a MicroDVI connector, the profiles of the connector insert  200  and connector receptacle  215  are shorter, or narrower, or both shorter and narrower, than a standard DVI connector. 
         [0032]    The connector receptacle  200  comprises an opening  220  that is bounded by a frame  215 . The frame  215  may be made of metal or other conductive or nonconductive material. The opening includes a board  230 . This board  230  may be a PC board made of an insulating or other type of material. The board  230  may have a number of pins  235  on one or both sides. The board  230  may also have pins on the ends, though such pins are not shown in this example. 
         [0033]    The connector receptacle  200  in this example includes a finger  240  and two keys  245 , though in other embodiments of the present invention, other numbers of fingers and keys may be used. In yet other embodiments of the present invention, one or more keys or one or more fingers may be used. For example, fingers may be included on the top, bottom, or sides of the connector to apply pressure and ensure a secure mating between the insert and receptacle during use. These fingers and keys may be made of metal, for example, they may be stamped or otherwise formed as part of the connector receptacle frame, or they may be made of other materials. 
         [0034]    The connector insert  215  is typically solid having an opening  250  in which the board  230  is inserted during use. The opening  250  may have pins  255  on its top and bottom. Also, the opening  250  may have pins on the sides, though such pins are not shown in this example. The connector insert  215  may be enclosed in a sheath  260  that is made of metal or other material. The sheath  260  may at least partially surround an insulating material such as plastic, such that the pins do not electrically short to the sheath. 
         [0035]    The connector insert  215  includes a wider portion  265  and a narrower portion. The narrower portion is narrower where a portion has been cut, shown here as a cutout portion  270  on each end of the connector insert  215 . 
         [0036]    When the connector insert  215  is properly inserted into the connector receptacle  200 , the cutout portion  270  of the connector insert  215  avoids the keys  245  in the connector receptacle  200 . When the connector insert  215  is improperly inserted, that is, it is inserted upside down, the wider portion  265  of the connector insert  215  is blocked by the keys  245 , thereby preventing insertion and possible resulting damage to the connector or connected electronic devices. 
         [0037]    As the connector insert  215  is inserted into the connector receptacle  200 , the finger portion  240  of the connector receptacle  200  provides a level of resistance to the user. As the connector insert  215  is inserted past a point, the finger  240  releases this resistance, thereby indicating to the user that the connector insert  215  is properly seated in the connector receptacle  200 . Fingers and keys are explained further in the following figures. 
         [0038]      FIG. 3  illustrates two keys  300  in a connector receptacle  320  according to an embodiment of the present invention. In this example, two keys  300  are shown, one on each side of the connector receptacle  320  opening. These keys  300  may be formed by stamping. Alternately, these keys  300  may be formed using another appropriate method. While in this example, the keys  300  are shown as rectangular in nature, in practical receptacles  320 , these keys  300  may be curved, triangular in nature, or they may have other shapes. 
         [0039]    Specifically, the shape of the keys  300  as viewed from the front of the connector receptacle  320  may be rectangular, curved, or it may have other shapes. Further, viewed from the side of the connector receptacle  320 , the keys  300  may also be rectangular, curved, or may have other shapes. The keys  300  may be recessed from the front of the opening of the connector receptacle  320 . It is desirable that when a connector insert is inserted backwards, or upside down, that the keys  300  give the user a clear indication that the connector insert is being incorrectly inserted. That is, the key or keys  300  should provide a non-reversible connection rejection feature. It is also desirable that the keys  300  block insertion in such a way as to prevent damage to the connector receptacle board (not shown) and related circuitry. In a specific embodiment, the key  300  prevents an incorrectly inserted connector insert from breaking the face plane of the connector receptacle  320 . 
         [0040]      FIG. 4  illustrates top, side, and front views of a finger  400  on a connector receptacle according to an embodiment of the present invention. As can be seen from the top view, the finger  400  can be formed by removing a cutout portion  410  on one side of the connector receptacle. In a specific embodiment of the present invention, the cutout portion  410  is removed on the top of the connector receptacle, though in other embodiments of the present invention, it may be located on another side of the connector receptacle. As shown in this example, the finger  400  includes an indented portion that is bent into the cavity formed by the connector receptacle inner wall, though in other embodiments, other shapes may be used. 
         [0041]    As a connector insert is inserted into the front opening  420  of the connector receptacle, the finger  400  provides an initial resistance to the user. As the user pushes the connector insert into the connector receptacle, the finger  400  deforms roughly along the axis of deformation  430  as shown. When the connector insert reaches the tip of the finger  400 , the finger  400  stops providing resistance and the insert can either continue to be pushed in, or is at this point completely pushed in, depending on the specific implementation used. This provides tactile feedback to the user that the connection has been made and improves the user experience. In a specific embodiment of the present invention, the tactile experience is akin to that of a snap, letting the user know that a connection has been achieved. That is, the finger  400  provides cognitive feedback that a connection has been made. 
         [0042]    Once the connector insert has been correctly inserted into the connector receptacle, it is desirable that this connection has a high degree of mechanical stability. Accordingly, embodiments of the present invention employ additional fingers to provide this stability. In a specific embodiment, four additional fingers (not shown) are used. Two of these fingers are on the top of the connector receptacle and two of these fingers are on the bottom. The fingers are all oriented in a direction opposite the finger shown in  FIG. 4 . Specifically, these fingers point towards the back of the receptacle, away from the receptacle opening. When inserted, these fingers apply an amount of pressure to the top and bottom of the connector insert, thus providing the desired stability. 
         [0043]      FIG. 5  illustrates the deformation of a finger as a connector insert is inserted into a connector receptacle according to an embodiment of the present invention. As can be seen in the side view of the connector receptacle before insertion, the finger  500  blocks the connector insert  520  as it is fitted into the connector receptacle  510 . The finger  500  deforms out of the way, again roughly along the axis of deformation  525  as shown, once the connector insert  520  is inserted into the connector receptacle  510 . 
         [0044]    Again, this finger  500  provides resistance once the connector insert  520  reaches the leading edge  530  of the finger  500 , and stops providing resistance once the connector insert leading edge  535  passes the tip of  FIG. 540 . It should be noted that while the finger  500  has a particular shape in these examples, fingers may have other shapes in other embodiment of the present invention. For example, rather than coming to a point, a finger may have a more rounded point. Alternately, it may have a more rectangular or squared edge. 
         [0045]      FIG. 6  illustrates a board  600  located in a connector receptacle  610  according to an embodiment of the present invention. The board  600  has a number of pins  620 , which may alternately be referred to as pads, on one or both sides. The pins  620  may be formed using surface mount technology or other appropriate method. The pins  620  on each side may have different sizes and spacing to adjacent pins as compared other pins on that side. Also, in embodiments where pins are on both sides, the pins on one side may have different sizes and spacings as compared to pins on the other side. 
         [0046]    In a specific embodiment of present invention, in a general manner, the analog and related pins are on one side of the board, while the digital and related pins are on the other side of the board. For example, analog pins for a DVI connector that are meant to drive a VGA monitor may be on one side of the board, while digital pins intended to drive a digital monitor may be located on the other side of the board. 
         [0047]    In this embodiment of the present invention, the analog pins are inactive when a digital monitor is being driven and the digital pins are inactive when an analog monitor is driven. Accordingly, only one set of pins is used at a time. Since pins on only one side of the board are active at a time, crosstalk from one side of the board to the other is not problematic. Since this crosstalk is not a concern, the rows can be closer together, that is, the board itself can be thinner. This reduces the height of the connector. In other embodiments of the present invention, both may be used simultaneously. In such an embodiment, a y-cable may be used to separate VGA and Transition Minimized Differential Signaling (TMDS) signals to their respective monitors. 
         [0048]      FIG. 7  illustrates a specific pinout employed by a connector receptacle according to an embodiment of the present invention. Again, in this example, the pins used to drive a digital display are primarily located on the top of the board, while the pins used to drive to an analog VGA display are primarily located on the bottom of the board. More specifically, when a digital or DVI monitor is driven, the active pins include pins 1-17 along the top, and pins 18 and 34 at the corners on the bottom. When an analog or VGA monitor is being driven, the active pins include pins 18-33 along the bottom, and 1, 15, and 16 near the corners at the top. The grounds can also be considered active in both modes of operation. 
         [0049]    On the top side of the board, the digital differential pins are kept together as adjacent pins. Each differential pair is isolated from nearby differential pins by a ground pin. This is true for the TMDS0, TMDS1, and TMDS2 pins. It is also true for the TMDS clock signals. On the bottom side, the VGA red, green, and blue pins are isolated by ground return lines and no-connects. These no connects may be open spots on the board, or there may be a pin that is not connected. In other embodiments of the present invention, these no connects are tied to each other. In still other embodiments of the present invention, they may also be tied to a shield, frame, sheath, or other appropriate ground. Also in this embodiment, each ground for each VGA color is routed back though the cable or dongle as a separate wire. This prevents ground drops from a color output from disturbing the other color outputs. 
         [0050]    This specific embodiment of the present invention provides a single link DVI interface. Other embodiments of the present invention provide a dual link interface. Also, in the future, other types of interfaces will be developed, and connector receptacles and connector inserts according to embodiments of the present invention may be used for those as well. 
         [0051]    In a specific embodiment of the present invention, the differential pins are separated from each other by a distance that allows a specification of transmission line impedance to be met. In one embodiment, this specification requires a differential impedance of 100 ohms plus or minus 10 percent over frequency, up to a frequency of 2.2 GHz. Similarly, the VGA red, green, and blue pins are separated from each other and ground lines such that a specification of 75 ohms may be met up to a frequency of 2.5 GHz. This separation also reduces near-end and far-end crosstalk, thereby improving signal integrity. 
         [0052]    In a specific embodiment of the present invention, the minimum pitch for each row is 0.5 mm, while the spacing is varied to meet the above impedance requirements and other parameters. Specifically, the signal to ground (return) pin spacing for the VGA red, green and blue signals are increased, relative to the spacing of the digital signals, so as to maintain a 75 ohm impedance at frequencies below 2.5 GHz. In this embodiment, the overall height of the board and pins is equal to or less than 4.64 mm, though in other embodiments of the present invention, other pitches and other heights may be used. Also, as described above, the pitch and separation of these pins may be varied. An example of this is shown in the following figure. 
         [0053]      FIGS. 8A-8B  illustrate a side view of through-hole and surface-mount pins according to an embodiment of the present invention.  FIG. 8A  illustrates two pins  820  and  830 . Pin  820  is located on the top of the board  810 , while pin  830  is located on the bottom of board  810 . Pin  820  is a surface-mount pin, while pin  830  is a through-hole pin. These pins may have the same depth, that is, pin  820  may be located directly above pin  830 , or they may be offset from each other. Again, this is a side view. In various embodiments of the present invention, these pins may be substantially flat, that is they appear as lines in the other dimensions, though in other embodiments of the present invention, they may have other shapes. 
         [0054]      FIG. 8B  also illustrates two pins  820  and  840 . Pin  820  is located on the top of the board  810 , while pin  840  is located on the bottom of board  810 . Pin  820  is a surface-mount pin, while pin  840  is a through-hole pin. These pins may have the same depth, that is, pin  820  may be located directly above pin  840 , or they may be offset from each other. 
         [0055]    The shape of pins  830  and  840 , that is, the manner they are bent or routed, allows these lines to have approximately the same length. Having the same length means that signals on pins  830  and  840  have the same delay. That is, pins  830  and  840  contribute the same amount of delay to their respective signals. This is particularly important when carrying differential signals, such as the differential digital signals used in DVI signaling. This promotes signal integrity and reduces the generation of EMI. 
         [0056]      FIG. 9  illustrates side, front, and top views of three pins  920 ,  930 , and  940 . These pins correspond to pins  820 ,  830 , and  840 . Pin  920  is located on the top of the board  910 , while pins  930  and  940  are located on the bottom of board  810 . Pin  920  is a surface-mount pin, while pins  930  and  940  are through-hole pins. 
         [0057]    Pins  930  and  940  are bent or routed in such a manner that they terminate at points that are at a distance from each other. Again, if these differential pair lines were closer, the solder used to make an electrical connection in the through holes may create shorts, thereby reducing yield. Having pins  930  and  940  terminate at a distance prevents solder bridging between them when they are connected to a board or other substrate. The shape of these pins also allows the pins  930  and  940  to be close to each other in a direction along the face of the connector receptacle. This arrangement allows the board to be manufactured with a high yield while reducing the linear space along the front of the connector. Additionally, mutual inductance between the pins is reduced by virtue of the reduced loop-area between adjacent pins. This again promotes signal integrity and allows connectors provided by embodiments of the present invention to achieve a high level of signal integrity and manufacturability, as well as a reduced level of EMI. 
         [0058]    The pins  920 ,  930 , and  940  may be soldered to a board internal to the electronic device. This board may be a flex connector, PC board, or other appropriate substrate. In a specific embodiment of the present invention, the connector receptacle has three rows of contacts to the internal board. Two of these rows are through-hole pins that are inserted into the connecting PC board, flex board, or other substrate. These rows include pins  930  and  940 . The outside most row of pins are surface-mount pins. This row includes pin  920 . This arrangement allows for inspection of the connection of the connector receptacle to the substrate. 
         [0059]    In a specific embodiment of the present invention, the through-hole pins are used for analog signals, in particular to carry analog VGA signals. In this embodiment, the digital differential DVI signals are assigned to the surface-mount pins,  920 . 
         [0060]    Specifically, with the connector receptacle on the top of the substrate, the through-hole pins can be inspected for contact to the bottom of substrate. Also from the top, the surface mount connection to the top of the substrate can be inspected. These connections are accessible and can therefore be reworked in the case of a soldering error. 
         [0061]      FIGS. 10-14  are mechanical diagrams of a connector receptacle according to an embodiment of the present invention. The particular dimensions shown provide a connector having a high level of manufacturability. They also provide a connector receptacle having a high level of signal integrity and impedance matching. They also provide a connector receptacle having a reduced EMI. 
         [0062]    The above description of exemplary embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.