Abstract:
Sensor systems and methods are disclosed, including first and second sensing elements element co-located on a leadframe structure with respect to a particular target. In general, target-specific sensing applications can be determined by varying the distance between the first and second sensing elements on the leadframe structure with respect to a common datum point thereof in order to provide speed and direction detection data from the first and second sensing elements with respect to the particular target.

Description:
TECHNICAL FIELD 
   Embodiments are generally related to sensing methods and systems. Embodiments are also related to quadrature sensor methods and systems. Embodiments are additionally related to Hall effect sensing devices and speed and direction sensors. 
   BACKGROUND OF THE INVENTION 
   Many different types of position sensors have been implemented in commercial, industrial and consumer applications. Some position sensors are intended to detect the movement of a target along a linear path while others detect the rotation of a target, such as a gear with a plurality of teeth, about an axis of rotation. The target and sensor can be arranged so that the target is provided with a plurality of magnetic poles that are sensed by a magnetically sensitive component. Alternatively, the sensor may be provided with a biasing magnet and the target can comprise a plurality of ferromagnetic discontinuities, such as gear teeth, that are sensed by the device. 
   One particular type of position sensing device is based on quadrature sensing, which involves the use of two signals that are offset from each other by 90 degrees so that a comparison of the signals will provide meaningful information with regard to the position of a target. Quadrature sensors generally provide two outputs that are 90 degrees out of phase. The rising and falling edges, of the output signals are generally utilized to determine the speed while the phase shift between the two output signals indicates direction of movement or rotation of the target. The two outputs can be obtained from two sensing elements that are physically spaced at a set distance to match an application-specific target. 
   The spacing of the sensing elements with respect to one another and the absolute placement of the sensing elements within the sensor package are critical to sensor&#39;s proper functioning. Maintaining the placement of the individual sensing elements often requires significant mechanical keying that is costly and inaccurate. Such mechanical features may also need to be recreated for each application. The physical size of the two sensing elements and associated mechanical features also limits how small the overall sensor can be made. 
   BRIEF SUMMARY OF THE INVENTION 
   The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
   It is, therefore, one aspect of the present invention to provide an improved sensor method and system. 
   It is another aspect of the present invention to provide an improved quadrature sensor, including methods and systems thereof. 
   It is yet another aspect of the present invention to provide a quadrature sensor device that utilizes Hall effect sensing elements in a common package or chip carrier. 
   The aforementioned aspects of the invention and other objectives and advantages can now be achieved as described herein. Sensor systems and methods are disclosed, including first and second sensing elements co-located on a leadframe structure with respect to a particular target. In general, target-specific sensing applications can be determined by varying the distance between the first and second sensing elements on the leadframe structure with respect to a common datum point thereof in order to provide speed and direction detection data from the first and second sensing elements with respect to the particular target. 
   In one particular embodiment, such a distance can be, for example, approximately one half the width of a target feature. The first and second sensing elements are located on respective die pads attached to the leadframe structure. Such first and second sensing elements can be implemented as Hall effect sensing elements. The leadframe structure can be implemented as a leadless plastic chip carrier. 
   The leadframe structure itself can be configured as a common leadframe structure shared by the first and second sensing elements. The first and second sensing elements can be spaced at a distance with respect to one another to match an application-specific target. Also, the first and second sensing elements respectively can provide first and second outputs that are 90-degrees out of phase with respect to the particular target 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the embodiments disclosed herein. 
       FIG. 1  illustrates an example phase shift between first and second signals which can be generated by a quadrature sensor system, in accordance with embodiments of the present invention; 
       FIG. 2  illustrates a quadrature sensor system, which can be implemented in accordance with a first embodiment; 
       FIG. 3  illustrates a quadrature sensor system, which can be implemented in accordance with a second embodiment; 
       FIG. 4  illustrates a quadrature sensor system, which can be implemented in accordance with a third embodiment; 
       FIG. 5  illustrates a quadrature sensor system, which can be implemented in accordance with a fourth embodiment; and 
       FIG. 6  illustrates a sensing system, which can be implemented in accordance with a preferred embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment of the present invention and are not intended to limit the scope of the invention. 
     FIG. 1  illustrates an example phase shift between a first signal  104  and a second signal  106 , which can be generated by a quadrature sensor system, in accordance with embodiments of the present invention. A plurality of target features (teeth and slots) are depicted in  FIG. 1 . The teeth are assumed to possess a length of X and the slots are assumed to possess a length of Y. Signal  104  represents Output Signal A and signal  106  represents Output Signal B. “X” represents a length  108  while “Y” represents a length  110 . Similarly, “X” represents a length  112  and “Y” represents a length  114 . Thus, lengths  108 ,  112  each possess a length “X”. Lengths  110 ,  114  each possess a length Y. The phase shift between signal  104  (i.e., Signal A) and signal  106  (i.e., Signal B) is approximately equal to ½ the average feature width (e.g., approximately X/2 mm), or ½ the average feature width plus the slot width and the tooth width (e.g., approximately X/2+Y+X mm). 
     FIG. 2  illustrates a quadrature sensor system  200 , which can be implemented in accordance with a first embodiment. System  200  includes a first sensor element  202  and a second sensor element  203 . Sensor element  202  includes a plurality of pins  204 ,  206 ,  208 ,  210 ,  214 ,  216 ,  218 , and  220 . Sensor element  203  includes a plurality of pins  222 ,  224 ,  226 ,  228 ,  230 ,  232 ,  234 , and  236 . Each sensor element  202  and  203  can be implemented, for example, as an 8-pin SOIC sensing package containing one or more sensing elements thereof (e.g., Hall-effect sensing elements). Sensor elements  202  and  203  can be co-located in a common package (e.g., a chip carrier). 
   Sensor element  202  possesses a length X 3 . Sensor element  203  also possesses a length X 3 . One half the length of sensor packages  202  and  203  is represented in  FIG. 2  as X 1 . The entire distance from one end of sensor element  203  to the other end of sensor element  202  is represented by variable X 4 . The width of each package from pin end to pin end is represented by the variable X 2 . In this example, the center of the magnetic sensing element is assumed to be in the center of each package. Therefore the distance between the centerline of sensor element  202  to the centerline of sensor element  203  is expressed by variable X. The Phase shift between the output signals is directly a function of distance X as well as the rotational alignment of the elements with respect to the target. 
   Sensor elements  202  and  203  can be implemented as Hall-effect elements, which rely on the reaction between a current flowing between a first set of contacts and an orthogonally applied magnetic field to generate a voltage across a second set of contacts. Hall-effect elements are generally fabricated using a lightly doped n-type layer for heightened sensitivity to variations in magnetic field intensity. An example of a Hall-effect element, which can be adapted for use with one or more of the embodiments described herein is disclosed in U.S. Pat. No. 6,492,697, “Hall-effect element with integrated offset control and method for operating hall-effect element to reduce null offset,” which issued to Plagens et al on Dec. 10, 2002, and which is assigned to Honeywell International Inc. U.S. Pat. No. 6,492,697 is incorporated herein by reference. 
   The placement of sensing elements  202  and  203  with respect to one another and to a common data point provides very accurate and precise tolerances through standard die placement (e.g., pick-and-place). Changing the sensing element spacing for application specific targets is simply a matter of implementing a change in the die placement in the package. 
     FIG. 3  illustrates a quadrature sensor system  300 , which can be implemented in accordance with a second embodiment. Note that in  FIGS. 1–2 , similar or identical parts or elements are generally indicated by identical reference numerals. In the configuration of system  300 , two separate sensor elements  202  and  203  are co-located with respect to one another and a common data point. For example, the width of each sensing element  202  and  203  from pin to pin is represented by the variable Y 1 , while one half the distance (width) from the center of each package or sensor element  202 ,  203  to respective pins thereof is represented by the variable Y 2 . The distance between the end of pins  214 ,  216 ,  218 ,  220  of sensor element  202  and the end of pins  22 ,  224 ,  226 ,  228  of sensor element  203  is represented by the variable Y 3 . In this example, the center of the magnetic sensing element is assumed to be in the center of each package. Therefore the distance between the centerline of sensor element  202  to the centerline of sensor element  203  is expressed by the expression X/2. The Phase shift between the output signals is directly a function of distance X/2 as well as the rotational alignment of the elements with respect to the target. 
     FIG. 4  illustrates a quadrature sensor system  400 , which can be implemented in accordance with a third embodiment. In the embodiment of system  400 , a sensor element  402  includes pins  404 ,  406 ,  404 ,  410  while a sensor element  403  includes pins  412 ,  414 ,  416 ,  418 . The width of each sensor element  402 ,  403  is represented by the variable Y 1 , while one half of this width is represented by the variable Y 2 . Sensor element  402  is located a distance Y 3  from sensor element  403 . Sensor elements  402  and  403  can be co-located within a circular area  422 . 
     FIG. 5  illustrates a quadrature sensor system  500 , which can be implemented in accordance with a fourth embodiment.  FIG. 5  illustrates respective top, side and bottom views  502 ,  504  and  506 . In the configuration depicted in  FIG. 5 , two sensing element die  508  and  512  can be implemented in a common package  501  that includes pins  514 ,  516 ,  518 ,  520 ,  524  and pins  526 ,  528 ,  530 ,  532 ,  534 ,  536 . Sensing element die  508  includes pins  538 ,  540 ,  542 , and  544 , which respectively electrically communicate with pins  516 ,  518 ,  520 , and  522 . Similarly, sensing element die  512  includes pins  546 ,  548 ,  550 , and  552 , which respectively electrically communicate with pins  528 ,  530 ,  532 , and  534 . 
   Package  501  can be implemented, for example, as a common-lead frame with respective die attached pads, such as, for example, sensing element dies  508  and  512 . Sensing element die  508  and  512  can be implemented, for example, as Hall-effect sensing element or sensor die. The distance between die  508  and  512  is a function of the sensing application and is preferably one-half of the target feature width. Package  501  can be configured as a leadless plastic-chip carrier. Several application specific variations can be readily implemented by varying the features between die  508  and  512 . 
   With other conventional constructions, as depicted in  FIGS. 1–4 , costly and inaccurate mechanical keying features are required in fixtures or mating components. In the embodiment depicted in  FIG. 5 , however, the placement of the sensing elements with respect to each other and to a common datum point is held to be very accurate, while promoting precise tolerances (e.g., less than 0.05 mm) through standard placement of die  508  and  512 . The co-located dies  508  and  512  within a leadless plastic carrier such as package  501  allows the sensing elements  508  and  512  to be located in a very small area, allowing the overall sensor size to be reduced. Note that die  508  and  512  can be implemented, for example, as sensor elements  202 ,  203  of  FIGS. 2–3  or sensor elements  402 ,  403  of  FIG. 4 , depending upon design considerations. 
     FIG. 6  illustrates a sensing system  600 , which can be implemented in accordance with a preferred embodiment. System  600  generally includes a sensor element  608  co-located within a circular area  609  with a sensor element  610 . Sensor elements  608 ,  610  can be implemented, for example, as sensor elements  202 ,  203  of  FIGS. 2–3  or sensor elements  402 ,  403  of  FIG. 4  and/or sensing die  508  and  512  depicted in  FIG. 5 . Circular area  609  can be located at one end of a sensor package  601  that includes a sensor body  602 , a retaining portion  606  and a sensor portion  604 . A target  603 , which rotates as indicated by arrow  612 , contains a central point  614 . Sensor elements  608  and  610  are therefore co-located in a common package  601  with respect to each other and to a common datum point, such as, for example central point  614 . 
   The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered. 
   The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.