Patent Publication Number: US-2022239462-A1

Title: Sensor signaling of absolute and incremental data

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of and claims priority to and the benefit of U.S. patent application Ser. No. 16/952,215, entitled “Signaling Between Master and One or More Slave Components to Share Absolute and Incremental Data” and filed on Nov. 19, 2020, the entirety of which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     Sensors are used to monitor various parameters of a system. For example, in vehicle systems, parameters such as current, speed, angle, linear position, and rotational direction of an article associated with a control module, such as a power steering module, a fuel injection module, and an anti-lock brake module, are often monitored. The sensor output signal is provided to a system controller, such as an Electronic Control Unit (ECU), that processes the sensor output signal and may generate a feedback signal for desired operation of the control module. Conventionally, the sensor updates the sensed parameter periodically and the system controller polls the sensor for data as needed for processing. 
     SUMMARY 
     Described herein are sensor integrated circuits (ICs), systems, and techniques for communicating sensor output information including absolute data and incremental data that allow for faster data updating than traditionally possible. The absolute data can include sensor output information about a sensed parameter and the incremental data can indicate changes in the absolute data. The incremental data can take the form of a single signal transition, or edge or multiple signal transitions, or a pulse. Features include error communication by the incremental data, incremental data communication without a dedicated sensor connection, dynamic adjustment of incremental data resolution, and communication of additional information with the incremental data. 
     According to the disclosure, a sensor integrated circuit (IC) includes a sensing element configured to sense a parameter associated with a target, a processor coupled to the sensing element and configured to generate a sensed signal indicative of the parameter associated with the target, and an output module coupled to receive the sensed signal. The output module is configured to transmit absolute data on a message line at a first rate and transmit incremental data on one or more index lines at a second rate, wherein the second rate is faster than the first rate, wherein the incremental data comprises data associated with changes in the absolute data and wherein an edge or a pulse is used to indicate an incremental change has occurred in the absolute data. 
     Features may include one or more of the following individually or in combination with other features. The incremental data may include an indication of an error. The absolute data may include a Pulse Width Modulation (PWM) signal. The PWM signal may include an indication of an error. The error indication by the PWM signal may include one or more of changing the PWM signal to a high impedance signal, decreasing a frequency of the PWM signal, and setting a duty cycle of the PWM signal to a predetermined duty cycle. The error indication by the incremental data may include replicating the error indication by the PWM signal. The sensed parameter associated with the target may be a position of the target, the absolute data may be the position of the target, and the incremental data may be a change in the position of the target. The incremental data may include an indication of a direction of movement of the target and wherein a first direction is indicated by a first incremental data pulse width and a second direction is indicated by a second incremental data pulse width and wherein presence of an error comprises a change of a signal level of the incremental data. The incremental data may include an indication of a direction of movement of the target and wherein a first direction is indicated by a first incremental data signal level and a second direction is indicated by a second incremental data signal level and wherein presence of an error comprises a pulse width of the incremental data. The sensor IC may include a hysteresis block configured to provide hysteresis to the index line. Upon start up of the sensor IC, the absolute data has an initial value and wherein the incremental data may have an initial value corresponding to the initial value of the absolute data. A resolution of the incremental change may be adjustable. The resolution of the incremental change can be user-programmable. The sensed parameter associated with the target can be a position of the target, the absolute data can be the position of a target, the incremental data can be a change in the position of the target, and the resolution of the incremental change can be dynamically varied based on a speed of movement of the target. The sensor IC can be coupled to an electronic control unit (ECU) for transmission of the absolute data and the incremental data. The sensing element can include a transmitting coil and a receiving coil. The sensing element can include a magnetic field transducer comprising one or more of a Hall effect element and a magnetoresistance element. 
     Also described is a sensor integrated circuit (IC) including a sensing element configured to sense a parameter associated with a target, a processor coupled to the sensing element and configured to generate a sensed signal indicative of the parameter associated with the target, and an output module coupled to receive the sensed signal. The output module is configured to transmit absolute data on a message line at a first rate and transmit incremental data on the message line at a second rate, wherein the second rate is faster than the first rate, wherein the incremental data comprises data associated with changes in the absolute data. 
     Features may include one or more of the following individually or in combination with other features. The absolute data and the incremental data may have at least one of different signal levels or different pulse widths. An edge or a pulse may be used to indicate an incremental change has occurred in the absolute data. 
     According to a further aspect of the disclosure, a sensor integrated circuit (IC) having a power connection includes a sensing element configured to sense a parameter associated with a target, a processor coupled to the sensing element and configured to generate a sensed signal indicative of the parameter associated with the target, and an output module coupled to receive the sensed signal. The output module is configured to transmit absolute data on a message line at a first rate and transmit incremental data on the power connection at a second rate, wherein the second rate is faster than the first rate, wherein the incremental data comprises data associated with changes in the absolute data. 
     Features may include one or more of the following individually or in combination with other features. An edge or a pulse may be used to indicate an incremental change has occurred in the absolute data. 
     According to another aspect of the disclosure, a sensor integrated circuit (IC) includes a sensing element configured to sense a parameter associated with a target, a processor coupled to the sensing element and configured to generate a sensed signal indicative of the parameter associated with the target, and an output module coupled to receive the sensed signal. The output module is configured to transmit absolute data on a message line at a first rate and transmit incremental data on one or more index lines at a second rate, wherein the second rate is faster than the first rate, wherein the incremental data comprises data associated with changes in the absolute data and additional data. 
     Features may include one or more of the following individually or in combination with other features. The additional data may be associated with at least one of diagnostic data and synchronization data. The incremental data and the additional data may have at least one of different signal levels or different pulse widths. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features may be more fully understood from the following description of the drawings. The drawings aid in explaining and understanding the disclosed technology. Since it is often impractical or impossible to illustrate and describe every possible embodiment, the provided figures depict one or more illustrative embodiments. Accordingly, the figures are not intended to limit the scope of the broad concepts, systems and techniques described herein. Like numbers in the figures denote like elements. 
         FIG. 1  is a block diagram of a system to transmit absolute data and incremental data that includes an electronic control unit (ECU) and one or more integrated circuits (ICs); 
         FIG. 2  is a diagram of example incremental data according to a pulse mode and an edge mode; 
         FIG. 2A  is a diagram of example pulse mode incremental data to communicate direction; 
         FIG. 2B  is a table illustrating incremental data resolution options; 
         FIG. 3  is a diagram of example absolute data, incremental data, and host interpretation; 
         FIG. 4  is a diagram of example absolute data in the form of a SENT message and incremental data transmitted on a dedicated index line; 
         FIG. 4A  is a diagram of example absolute data in the form of a SENT message and incremental data transmitted on the same message line; 
         FIG. 4B  is a diagram of example absolute data in the form of a SENT message and incremental data transmitted on a power connection; 
         FIG. 4C  is a diagram of example absolute data in the form of a SENT message and incremental data transmitted on a dedicated index line and including additional data communicated by signal level; 
         FIG. 4D  is a diagram of example absolute data in the form of a SENT message and incremental data transmitted on a dedicated index line and including additional data communicated by pulse width; 
         FIG. 5  is a block diagram of an example system to transmit absolute data and incremental data; and 
         FIG. 6  is a block diagram of another example system to transmit absolute data and incremental data. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein are various sensors, systems, and techniques for communicating sensor output information including absolute data and incremental data that allow for faster data updating than traditionally possible. The absolute data can include sensor output information about a sensed parameter and the incremental data can indicate changes in the absolute data. The incremental data can take the form of a single signal transition, or edge or multiple signal transitions, or a pulse. Features include error communication by the incremental data, incremental data communication without a dedicated sensor connection, dynamic adjustment of incremental data resolution, and communication of additional information with the incremental data. 
     Referring to  FIG. 1 , a system  100  includes an electronic control unit (ECU)  102  (sometimes referred to as a “master component”) and one or more integrated circuits (ICs)  104   a - 104   n  (sometimes referred to as “slave components”). The ICs  104   a - 104   n  can be sensors of various types, such as, for example, a current sensor, a speed sensor, an angle sensor, a magnetic field sensor, a temperature sensor, a pressure sensor, a chemical sensor, a motion sensor, a rotational direction sensor, a position sensor, an optical sensor, and so forth. ICs  104   a - 104   n  may be the same type of sensor (e.g., each a magnetic field sensor) or may be different types of sensors (e.g., one is a temperature sensor and the others are magnetic field sensors). ICs  104   a - 104   n  may monitor the same or different target parameters. For simplicity, sensor ICs  104   a - 104   n  are described in connection with an example sensor  104   a.    
     Sensor  104   a  includes one or more sensing elements configured to sense a parameter associated with a target (as shown in  FIG. 5 ). Sensing elements may take various forms depending on the sensor type and application. For example, the sensing elements can include, but are not limited to magnetic field sensing elements, optical detectors, temperature sensors. The target can also take various forms. For example, in the case of a magnetic field sensor  104   a , a sensed target can take the form of a ring magnet or a ferromagnetic target (e.g., gear teeth) where the magnetic field sensor is used in combination with a back-biased magnet. The sensed parameter can be motion of the target, such as rotation and/or position of the target, such as an angular position, to name a few examples. For simplicity of explanation, features of the disclosure are described herein in connection with sensor  104   a  taking the form of an angular position sensor or simply angle sensor. 
     Sensor  104   a  further includes a processor coupled to the sensing element and configured to generate a sensed signal indicative of the parameter associated with the target. In the case of a magnetic field sensor for example, the sensed signal can be the output signal of a magnetic field transducer such as a Hall effect or magnetoresistance element. 
     An output module of the sensor  104   a  is coupled to receive the sensed signal and configured to transmit absolute data based on the sensed signal. Thus, the absolute data is indicative of the sensed parameter. 
     The incremental data can be data associated with predetermined changes in the absolute data (i.e., changes of a predetermined increment). For example, in the case of an angle sensor, the incremental data can indicate an incremental change in the sensed angle (e.g., an incremental change of a predetermined number of degrees, or ΔΘ). In one particular example, the absolute data is an angle measurement (e.g., 275°) and the sensor IC  104   a  sends incremental data each time there is, for example, an incremental change (e.g., a 0.2° change) in the absolute data. In another example, the absolute data is a magnetic field intensity (e.g., 100 Oersted) and the sensor IC  104   a  sends incremental data each time there is, for example, an incremental change (e.g., a 0.2 Oersted change) in the absolute data. 
     The absolute data is transmitted on message line  106  at a first rate. The incremental data is transmitted at a second rate that is faster than the first rate at which the absolute data is transmitted. For example, absolute data in the form of SENT messages can be sent on the message line  106  every 128 microseconds while the incremental data sent can be sent every 3 microseconds or even faster. The system  100  allows a faster response time to detect changes in the absolute data than traditional arrangements. 
     The format of the absolute data can be various unidirectional and/or bidirectional formats, including but not limited to Serial Peripheral Interface (SPI), Single-Edge Nibble Transmission (SENT), I 2 C, Pulse Width Modulation (PWM), ABI, to name a few. For example, a unidirectional SENT format may be used by the IC  104   a  to transmit absolute data to the ECU  102  on the message line  106 . In other examples, a bidirectional format (e.g., a triggered SENT or Manchester format) may be used by the IC  104   a  to transmit data to the ECU  102  on the message line  106  after receiving a request from the ECU  102 . 
     In some embodiments, the incremental data is transmitted on an index line  108  which can be considered a dedicated line for communication of incremental data as is described in connection with  FIGS. 4, 4C, and 4D . In some embodiments, the absolute data and the incremental data are transmitted on a shared line as described in connection with  FIG. 4A . And in some embodiments, the incremental data is transmitted on a power connection of the IC as described in connection with  FIG. 4B . In some embodiments, more than one index line  108  with incremental data can be used for purpose of safety, redundancy, or transients filtering. 
     It will be appreciated that while features are described herein with respect to a single sensor  104   a , the described features can be readily extended for use by more than one IC  104   b - 104   n  and/or with more than one ECU  102 . For example, in embodiments, a plurality of ICs  104   a - 104   n  can share a message line  106  and can have separate index lines  108  coupled to the ECU  102 . In embodiments, the index lines and the message lines associated with a plurality of ICs  104   a - 104   n  are coupled together and to the ECU  102 . Communication on shared index and/or message lines can be sequential (i.e., the ICs can take turns transmitting on the shared lines). IC and ECU configurations are described in a co-pending U.S. patent application Ser. No. 16/952,215, entitled “Signaling Between Master and One or More Slave Components to Share Absolute and Incremental Data” and filed on Nov. 19, 2020, the entirety of which is hereby incorporated herein by reference. 
     Referring also to  FIG. 2 , examples 200 of incremental data  204 ,  208  are shown. In some embodiments, incremental data  204  can include an edge  214  to indicate that an incremental change has occurred in the absolute data, as can be referred to as edge mode. In other words, in this example, each edge  214  (i.e., transition from one signal level to another) indicates an incremental change (e.g., a positive incremental change in the angular position of the target, +ΔΘ). In the example incremental data  204 , each edge (both a rising edge from a low state to a high state and a falling edge from a high state to a low state) indicates a positive incremental change in the absolute data. 
     Implementation of such edge based incremental data  204  can be achieved by pulling up or pulling down on the index line  108  ( FIG. 1 ) depending on the previous signal level when the detected position has changed by the incremental amount ΔΘ. 
     In other embodiments, the incremental data  208  can indicate that a change has occurred in the absolute data by transmitting a pulse  218 , as can be referred to as pulse mode. In other words, an incremental change in the absolute data can be communicated by a transition in the incremental data from a low state to a high state and back to a low state, as illustrated by pulses  218 . Alternatively, an incremental change in the absolute data can be communicated by the incremental data transitioning from a high state to a low state and back to a high state. 
     In some embodiments, the pulse width of pulses  218  can be selectable, such as by user programming of an EEPROM. The selected pulse width can impact the maximum target speed supported by the incremental data  208  as described below. 
     The maximum target speed supported by the incremental data is based on the maximum possible frequency for the index line  108  which is dependent on output load and the selected resolution ΔΘ for the incremental data. For example, in the case of edge mode incremental data  204 , the maximum target speed can be given by: 
       MAX_SPEED [electrical RPM]=2×MAX_ f   INC  [Hz]×ΔΘ [degrees]/6
 
     where MAX_f INC  is the maximum possible frequency for the index line  108  which is dependent on output load. 
     It will be appreciated by those of ordinary skill in the art that the maximum target speed is dependent on the line on which the incremental data is communicated to the ECU. For example, in embodiments in which the incremental data is transmitted on the message line along with the absolute data ( FIG. 4A ), it is the maximum possible frequency supported by the message line  106  that governs maximum target speed and in embodiments in which the incremental data is transmitted on a power connection ( FIG. 4B ), it the maximum possible frequency supported by the power connection that governs maximum target speed. 
     In the case of pulse mode incremental data  208 , the maximum target speed can be given by: 
       MAX_SPEED [electrical RPM]=1/(2 ×T   PULSE  [s])×ΔΘ [degrees]/6
 
     where T PULSE  is the pulse width which, as noted above, can be user selectable or programmable. 
     Referring also to  FIG. 2A , in the pulse mode, the sensor IC  104   a  may transmit incremental data  250  in a manner that indicates a change in direction of motion of a target by using a pulse width. For example, a pulse width of T PULSE  as shown for pulse  254  may indicate a clockwise direction of target motion while a pulse width of 3T PULSE  may indicate a change to a counterclockwise direction of target motion. Each pulse  254 ,  258 ,  264 ,  274  can communicate an incremental change in the absolute data; however, when the target is moving in the first (e.g., forward) direction, a communicated incremental change can be a positive change +ΔΘ, whereas when the target is moving in the second (e.g., reverse) direction, a communicated incremental change can be a negative change −ΔΘ. 
     In embodiments, the size of the increments indicated by the incremental data (i.e., the resolution) can be configurable, adjustable, and/or selectable, such as pre-programming the resolution or by user programming of an EEPROM. For example, the incremental change ΔΘ indicated by the incremental data can take values such as 0.2 degrees, 0.5 degree, and 1.0 degree in case of angular absolute information or for instance values of 1 mm, 2 mm or 5 mm in case of linear displacement absolute information. 
       FIG. 2B  shows a table  280  illustrating example selectable incremental data resolution options. In particular, each selectable incremental data resolution as listed in the first column  282 , has a corresponding incremental angle ΔΘ in units of degrees as listed in the second column  284 , and a corresponding angular resolution in bits as listed in the third column  286 . It will be appreciated by those of ordinary skill in the art that the table of  FIG. 2B  is illustrative only and the number of selectable resolutions and corresponding increments in angular degrees (or other units for absolute data other than angular position) and bits of resolution can be varied to suit a particular application. 
     In embodiments, resolution of the incremental data can be dynamically varied or adjusted, such as based on target speed for example. In other words, sensor IC  104   a  can provide a first resolution of incremental data for target speeds within a first range of speeds and can provide a second, different resolution of incremental data for target speeds within a second range of speeds different than the first range of speeds. In embodiments, the first resolution can be lower than the second resolution and the first range of target speeds can be faster than the second range of target speeds. 
     Referring also to  FIG. 3 , a diagram  300  illustrates example absolute data  310 , incremental data  320 , and host interpretation  330 . Absolute data  310  takes the form of a SENT signal including individual SENT messages  310   a - 310   c . For each SENT message  310   a - 310   c , incremental data  320   a - 320   c , respectively, communicates incremental changes (i.e., +INC) in the absolute data, here in an edge mode fashion, in which each edge of incremental data indicates an incremental change in the absolute data. 
     As noted above, the resolution of the incremental change +INC can be pre-programmed or user programmed. In an example, the first SENT message  310   a  indicates a starting target angle of 0 degrees and the incremental data  320  communicates incremental changes with a resolution of 0.1 degrees. The SENT messages  310   a - 310   c  can have a user specified tick time and message format. In an example in which the incremental data  320  is communicated on an index line  108  ( FIG. 1 ), the voltage on line  108  can be pulled up or pulled down depending on the previous status when the change in target position meets or exceeds the pre-programmed or user-programmed increment. 
     Also illustrated in  FIG. 3  is interpretation  330  of the absolute data  310  and incremental data  320  by the ECU  102  ( FIG. 1 ) and an example of retrieved incremental information  340 . Various schemes are possible for synchronizing the incremental data  320  to the absolute data  310 . As one example, the incremental data  320  is synchronized to the first SENT message  310   a  after power-on by a “count up feature”, following which the incremental data is free running after this first synchronization. In this example, the host (ECU  102 ) interprets the absolute data  310  and the incremental data  320  independently. 
     With this type of an independent synchronization scheme, for example in the case of an angle sensor and edge mode incremental data  320 , the ECU  102  counts edges of incremental data  320  during the first SENT message and interprets the resulting edge count as the initial target angle. In this way, the ECU can be considered to “count up” to the angle during this first message duration. For example, during the first SENT message, the incremental data  320  has two edges at times t 2  and t 3 . Thus, by the end of the first SENT message (at time t 4 ), the retrieved incremental information  340  yields a target angle interpretation of 0.2°, as shown. Following such synchronization during the first SENT message  310   a , the retrieved incremental information  340  increases by 0.1° each time an edge of incremental data occurs (e.g., at times t 5 , t 6 , t 7 , t 8 , t 10 , and t 11 ), as shown. 
     Another type of synchronization of the incremental data  320  to the absolute data  310  can be accomplished by synchronizing the incremental data to a previous SENT message. In one such example, the incremental data  320  is synchronized with a predetermined point of the previous SENT message (e.g., end of the synchronization nibble). In this synchronization scenario, the incremental data  320  represents an incremental change in the absolute data communicated in the prior SENT message. Consider an example in which a SENT message previous to the illustrated message  310   a  indicates an absolute target angle of 0 degrees. In this scenario, incremental data  320   a  occurring during SENT message  310   a  can indicate an incremental change to the previous SENT message indication of 0 degrees. Thus, each of the incremental data edges at times t 2  and t 3  can indicate an incremental change of 0.1 degrees to the 0 degrees communicated in the previous SENT message, so that by the end of the first SENT message (at time t 4 ), the retrieved incremental information  340  yields a target angle interpretation of 0.2° (i.e., computed as 0° from the previous SENT message +0.1° communicated by incremental data edge t 2 +0.1° communicated by incremental data edge t 3 ). Following such synchronization during the first SENT message  310   a , the retrieved incremental information  340  increases by 0.1° each time an edge of incremental data occurs (e.g., at times t 5 , t 6 , t 7 , t 8 , t 10 , and t 11 ), as shown. 
     It will be appreciated that in embodiments in which the incremental data  320  is communicated on a separate index line  108  ( FIG. 1 ), communication of incremental data can provide a safety feature whereby the target angle as communicated via the index line  108  can be compared to the target angle data as communicated by the SENT messages  310   a - 310   c  on the message line  106 . Thus, even if the message line  106  were to fail, incremental data can still be communicated via the index line  108  and vice versa, if there is a failure of the index line  108 , absolute data can still be communicated via the message line  106 . 
     Referring to  FIG. 4 , example absolute data  400  in the form of a SENT message is shown along with incremental data  412  transmitted on a separate, dedicated line, such as index line  108  ( FIG. 1 ). The SENT message  400  can include a sequence of pulses transmitted by the sensor IC  104   a  and in the example angle sensor, the target angle can be converted into the pulses with data encoded as falling to falling edge periods. SENT message  400  can include a Synchronization and Calibration portion  402 , a Status and Serial Communication portion  404 , a Data portion  406 , and a Checksum (or cyclic redundancy check, CRC) portion  408 . A “tick” refers to the nominal clock signal period and a “nibble” is 4 bits. Each nibble has a specified time for low and high state. The low state duration is by default 5 ticks and the high state duration is dictated by the information value of the nibble. The Synchronization and Calibration portion  402  identifies the start of the SENT message  400  and has a pulse duration of 56 ticks. Status and Serial Communication portion  404  is used to inform the ECU  102  of the sensor status or features (such as part numbers or error code information) and has a duration of between 12 and 27 ticks to provide 4 bits. Data portion  406  includes up to six nibbles of data, with each nibble containing 4 bits with values ranging from 0 to 15. Thus, each data nibble has a pulse duration from 12 to 27 ticks. The number of data nibbles will be fixed for each application but can vary between applications. In order to transmit two 12 bit values, 6 data nibbles are communicated, as shown. The SENT signal  400  includes an optional pause portion  410  that can be used to permit bidirectional communication. In general, the pause portion  410  corresponds to a period of inactivity on the sensor output, when the absolute data on the message line  106  ( FIG. 1 ) is inactive. The pause portion  410  is sometimes used to prolong the SENT signal to a constant length if desired. The user can program a particular desired frame rate. 
     Incremental data  412  can be edge based or pulse based. In the case of edge based incremental data, each edge  412   a - 412   f  can communicate an incremental change in the absolute data presented by SENT message  400 , such as each edge representing an increase of 0.1 degrees in the measured target angle. In the case of pulse based incremental data, each of the three illustrated pulses (i.e., a first pulse bounded by edges  412   a ,  412   b , a second pulse bounded by edges  412   c ,  412   d , and a third pulse bounded by edges  412   e ,  4120  can communicate an incremental change in the absolute data  400 . 
     Referring to  FIG. 4A , in some embodiments, absolute data and incremental data are transmitted on a shared line as a combined, or composite signal  420  in which different signal levels can be used to communicate the absolute data and the incremental data. For example, absolute data can be transmitted by a signal level range of between 1V to 4V and incremental data can be transmitted by a different signal level range, such as between 0V to 1V when the SENT signal is low and between 4V to 5V when the SENT signal is high. The absolute data in the form of a SENT signal can include a Synchronization and Calibration portion  422 , a Status and Serial Communication portion  424 , a Data portion  426 , and a CRC portion  428 , and an optional pause portion  430 . 
     The incremental data  434  of the combined signal  420  can be edge based in which case each of edges  434   a - 434   y  represents and communicates an incremental change in the absolute data. Alternatively, the incremental data  434  can be pulse based in which case each pulse as represented by adjacent edge pairs (e.g., a pulse represented by edge pairs  434   a ,  434   b  and a pulse represented by edge pairs  434   c ,  434   d ) represents an incremental change in the absolute data. 
     An ECU  102  ( FIG. 1 ) receiving composite absolute and incremental data signal  420  can decode the absolute data using a threshold level of approximately 2.5V. The incremental data  434  can be decoded using additional thresholds of 0.5V and 4.5V, for example. 
     Transmitting absolute and incremental data on a single line  420  is particularly advantageous in applications requiring fewer wires, or connections while still communicating SENT and faster incremental information. For example, in this embodiment, the sensor IC  104   a  can include only three connections; namely a power, or VCC connection, a ground connection, and a single output connection. 
     Referring to  FIG. 4B , in some embodiments, the incremental data can be transmitted on a power connection of the sensor IC  104   a . In this example, absolute data  440  in the form of a SENT signal can include a Synchronization and Calibration portion  442 , a Status and Serial Communication portion  444 , a Data portion  446 , a CRC portion  448 , and an optional pause portion  450 . 
     The incremental data  452  can take the form of current pulses transmitted on the VCC and/or ground connections of the IC  104   a  ( FIG. 1 ). In one example embodiment, data is communicated by 2 mA current pulses (i.e., ICC) on the power connection VCC. 
     In an edge based incremental data example, each edge  452   a - 452   f  of the incremental data  452  can communicate an incremental change in the absolute data. Alternatively, in a pulse based incremental data example, each pulse as represented by adjacent edge pairs (e.g., a pulse represented by edge pairs  452   a ,  452   b  and a pulse represented by edge pairs  452   c ,  452   d ) represents an incremental change in the absolute data. 
     An ECU  102  ( FIG. 1 ) receiving incremental data  452  can decode the incremental data using current comparator circuitry and techniques. 
     Transmitting incremental data  452  on a power connection (e.g., as current pulses ICC) is advantageous in applications requiring fewer wires, or connections while still communicating SENT and faster incremental information. For example, in this embodiment, the IC  104   a  can include only three connections; namely a power, or VCC connection, a ground connection, and an output connection on which the absolute data is transmitted. 
     Referring also to  FIG. 4C , example absolute data  454  in the form of a SENT message is shown along with incremental data  466  transmitted on a separate, dedicated index line, such as index line  108  ( FIG. 1 ) and including additional absolute data  470  communicated by signal level. The SENT message  454  can include a Synchronization and Calibration portion  456 , a Status and Serial Communication portion  458 , a Data portion  460 , a CRC portion  462 , and an optional pause portion  464 . 
     The incremental data  466  can be edge mode data, such that each edge  466   a - 466   k  can communicate an incremental change in the absolute data  454 , such as the illustrated incremental change of 0.5 degrees of rotation of the sensed target. 
     The additional absolute information  470  transmitted with the incremental data  466  can communicate various data. Examples include synchronization data, such as absolute angular position of the sensed target at predetermined angular positions, such as every 360° or every 120°, diagnostic information, or other additional information. 
     The additional absolute information  470  transmitted with the incremental data  466  can be communicated in various ways, such as by signal level excursions beyond the nominal level of the incremental data  466 , as shown. For example, incremental data  466  can be transmitted by a signal level range of between 1V to 4V and additional absolute date  470  can be transmitted by a different signal level range, such as between 0V to 1V when the incremental data  466  is low and between 4V to 5V when the incremental data  466  is high. 
     In the case of the additional data being a predetermined angular position of the sensed target, an excursion of the additional data  470  from 5V to 0V (as labeled  470   b ,  470   c ) can indicate a target position of 360° for example. It will be appreciated that an excursion of the additional data  470  from 0V to 5V could alternatively be used to indicate the predetermined target position of 360° or other additional information intended to be communicated with the incremental data  466 . 
     Referring also to  FIG. 4D , example absolute data  474  in the form of a SENT message is shown along with incremental data  486  transmitted on a separate, dedicated index line, such as index line  108  ( FIG. 1 ) and including additional absolute data communicated by pulse width. The SENT signal can include a Synchronization and Calibration portion  476 , a Status and Serial Communication portion  478 , a Data portion  480 , a CRC portion  482 , and an optional pause portion  484 . 
     The incremental data  486  can be pulse mode data, such that each pulse  486   a - 486   n  can communicate an incremental change in the absolute data  474 , such as the illustrated incremental change of 0.5 degrees of rotation of the sensed target. 
     The additional absolute information transmitted with the incremental data  486  can communicate various data. Examples include synchronization data, such as absolute angular position of the sensed target at predetermined angular positions, such as every 360° or every 120°, diagnostic information, or other additional information. 
     The additional absolute information transmitted with the incremental data  486  is communicated by pulse width. For example, incremental data pulses that communicate an incremental change in the absolute data  474  can have a first nominal width as shown for pulses  486   a - 486   f  and  486   h - 486   n  and the additional absolute information can have a second, different pulse width as shown for wider pulse  486   g . It will be appreciated that while the second pulse width is shown to be larger than the first, nominal pulse width, the alternative is possible with the first, nominal pulse width being the larger pulse width. 
     In the example case of the additional absolute data being a predetermined angular position of the sensed target, occurrence of a pulse  486   g  having the second width can indicate a target position of 360° for example. It will be appreciated that while occurrence of a pulse  486   g  having the second width is illustrated as communicating a predetermined absolute angular target position of 360°, in other embodiments, a pulse having the second width can communicate diagnostic or other additional information. 
     Referring also to  FIG. 5 , an example system  500  to transmit absolute data and incremental data includes a sensor IC  510  proximate to a target  514 . The sensor IC  510  can be the same as or similar to IC  104   a  of  FIG. 1  and can implement one or more of the above-described schemes for transmitting absolute and incremental data between the IC and a control unit (not shown in  FIG. 5 , but which control unit can be the same as or similar to ECU  102  of  FIG. 1 ). 
     One or more sensing elements  520   a ,  520   b  is configured to sense a parameter associated with the target  514 . For example, each of sensing elements  520   a ,  520   b  can sense a position and/or movement of target  514 . A sensed signal  522   a ,  522   b  generated sensing elements  520   a ,  520   b  can be processed by respective front-end circuitry including an amplifier and filter  524   a ,  524   b  and an analog-to-digital converter (ADC)  526   a ,  526   b , respectively. Each signal path from sensing element to ADC can be referred to as a channel and provides a respective converted signal  528   a ,  528   b . Use of multiple channels in the sensor IC  510  can be used to determine a direction of motion (e.g., rotation) of target  514 . 
     Sensing elements  520   a ,  520   b  can take various forms and can include more or fewer than the illustrated two sensing elements in various configurations such as bridge configurations. For example, in applications in which the sensor  510  is a magnetic field sensor, sensing elements  520   a ,  520   b  can take the form of one or more of a giant magnetoresistor (GMR), a tunnel magnetoresistor (TMR), a Hall effect element, a pickup coil, and/or any other suitable type of magnetic field sensing element. Sensing element  520   a  may have a first axis of maximum sensitivity and sensing element  520   b  may have a second axis of maximum sensitivity that is perpendicular to the first axis of maximum sensitivity. As a result of this arrangement, a signal generated by sensing element  520   a  may have a sinusoidal waveform and a signal generated by sensing element  520   b  may have a cosinusiodal waveform, rendering the resulting signals  528   a ,  528   b  responsive to orthogonal field components (i.e., in quadrature). 
     Memory  534  can be configured to store various values for use during sensor operation, some of which can be user-programmable. In embodiments, memory  534  can take the form of a non-volatile memory, for example, an EEPROM. 
     A digital processor  530  can be coupled to receive respective processed and converted signals  528   a ,  528   b  and can be configured to perform various processing, depending on the type of sensor IC  510  and application. For example, amplitude and offset compensation can be performed on converted signals  528   a ,  528   b  in order to implement gain and offset adjustments to compensate for gain mismatches between the processing channels and offsets introduced by the sensing elements  520   a ,  520   b , respectively. The amplitude and offset corrections can also adjust gain and offset based on temperature variations and other factors. To this end, sensor  510  can include a temperature sensor (not shown). Adjusting the gain of signals  528   a ,  528   b  may include multiplying the respective signal by a gain adjustment coefficient as may be stored in memory  534  and offsetting the signals  528   a ,  528   b  may including adding an offset adjustment coefficient as may be stored in memory to the respective signal. It will be understood that the present disclosure is not limited to any specific methodology for offset and/or a gain adjustment. 
     Harmonic compensation can be implemented by processor  530  in order to compensate for error in calculated signals (e.g., error in a calculated angle signal). For example, error can be expressed in its harmonic terms after performing a Fourier transform. Compensation for harmonic errors can be performed by generating coefficients (e.g., coefficients representing the phase and magnitude of each harmonic error term) that can be stored in memory  534  and selectively applied to the calculated signal. For example, in a manufacturing setting, data from a single rotation of the target  514  that is measured by a proximate angle sensor  510  can be stored and used to generate the harmonic compensation coefficients by performing a Fast Fourier Transform (FFT) on the collected data. In this way, the error can be recreated and used to compensate the calculated signal (e.g., by applying the recreated harmonic error terms to the computed angle). It will be understood that the present disclosure is not limited to any specific methodology for harmonic compensation. 
     Processor  530  can perform a speed calculation whereby a speed of motion (e.g., rotation) of the target  514  can be determined, such as by comparing one or both converted signals  528   a ,  528   b  to a threshold signal. Direction calculation can be performed in various ways. For example, a direction of rotation of the target  514  can be determined by the phase relationship between the converted signals  528   a ,  528   b  whereby a first direction of rotation can correspond to signal  528   a  leading signal  528   b  and a second, opposite direction of rotation can correspond to signal  528   a  lagging signal  528   b . It will be understood that the present disclosure is not limited to any specific methodology for target speed and/or direction calculation. 
     An angle of target  514  also can be determined in various ways, for example, by performing CORDIC processing on converted signals  528   a ,  528   b . It will be understood that the present disclosure is not limited to any specific methodology for angle calculation. 
     Additional processing by processor  530  can include maintaining a turns count register to indicate a number of rotations experienced by the target  514 . To this end, turns counter logic can be responsive to the speed signal and to the direction signal in order to determine when to increment or decrement the turns counter. The angular change for which the register is incremented/decremented can be programmable. For example, in the context of a vehicular electronic steering system, memory  534  can be continuously updated in order to track and update the position of a steering wheel. Circuitry used in some electronic steering systems includes a so-called “turns count register” that is used to keep count of a number of wheel turns beyond 360 degrees e.g. the number of turns made by a gear tooth. 
     Processor  530  can implement diagnostic monitoring in order to detect faults or errors for reporting to ECU  102  and/or for initiating other appropriate action for example. A fault may include one or more of: a supply voltage under voltage condition, a voltage check failure, a supply voltage over voltage condition, a temperature sensor error, a magnet sense high, a saturation current, a magnet sense low, a signal path mismatch condition, a memory error condition, an error of the absolute data, a slew rate warning, oscillator frequency error, to name a few. 
     Processor  530  can implement dynamic incremental data resolution adjustment, for example based on target speed as explained above. In other words, sensor IC  510  can provide a first resolution of incremental data for target speeds within a first range of speeds and can provide a second, different resolution of incremental data for target speeds within a second range of speeds different than the first range of speeds. It will be appreciated that the calculated target speed can be used for this purpose. 
     Processor  530  can implement hysteresis on the incremental data in order to avoid inaccurate or false incremental data transitions (i.e., edges or pulses). For example, hysteresis on the incremental data can avoid falsely indicating an incremental change in the absolute data when such an incremental change has not occurred and/or can avoid falsely indicating a target motion direction change. 
     In embodiments, errors are communicated via the incremental data. Errors may additionally or alternatively be communicated as part of the absolute data. 
     Processor  530  can implement a “count up” feature with which the incremental data catches up with the absolute data first detected upon power up of the sensor  510  and output on the absolute data message line  106  ( FIG. 1 ). The count up feature is advantageous in embodiments in which the absolute data is not reset to a predetermined value such as zero after a power on reset. In such situations in which it is not possible to ensure an initial absolute data value, the count-up feature can synchronize the incremental data with the actual data using a slew rate feature. After power-up, using slew rate, the incremental data (i.e., index line  108  of  FIG. 1 ) can inject fast “fake” pulses toward actual data until the incremental data matches the absolute data. For example, in the case of angle measurements, the incremental data can constantly emit “fake” pulses in the closest direction towards the current angle position (e.g., if the current angle position is 270°, the incremental data will increment in a direction towards this value effectively counting down from 360°). An example of this feature is illustrated by retrieved incremental data  340  during the first SENT frame in  FIG. 3 . 
     Output module  540  can be coupled to receive one or more signals from digital processor  530  and generate one or more sensor output signals  550  to communicate the sensed parameter in the form of absolute data and incremental data to external systems, such as ECU  102  ( FIG. 1 ). The sensor output signals  550  may optionally include additional information such as direction and diagnostics for example. 
     Sensor output signals  550  can take various formats such as SENT, PWM, SPI, and ABI to name a few. The sensor output signal format can be programmable. 
     SENT and PWM output formats can have the incremental data provided on the same signal line as the absolute data (e.g., as shown in  FIG. 4A ) and can utilize a three wire output configuration in which the absolute data and the incremental data can be provided together on a dedicated output signal line or can utilize a two wire configuration in which the absolute and incremental data can be provided together on a power and/or ground connection  546 ,  548  as may be coupled to power systems  544  including regulation circuitry. For example, such two wire transmission can take the form of current pulses on the power and/or ground connection  546 ,  548  as shown in  FIG. 4B . SPI and ABI output signal formats can be communicated on signal lines with incremental data on a separate output signal line than the absolute data. It will be appreciated by those of ordinary skill in the art that other output signal formats and connection configurations are possible to suit application requirements. 
     In an example embodiment, the sensor output signal  550  is a PWM signal having a duty cycle proportional to the target angle. The PWM frequency and falling edge time can be programmable in memory  534 . 
     In this example, the PWM output signal  550  can include an indication of a detected error and can do so in various ways. For example, an error can be communicated by changing the PWM signal to a high impedance signal, by decreasing a frequency of the PWM signal, or by setting a duty cycle of the PWM signal to a predetermined duty cycle. Incremental data provided on a separate signal line from the absolute PWM signal can additionally provide an indication of the detected error and can do so in the same manner as the error is indicated in the PWM signal; namely by changing the signal to a high impedance signal, by decreasing a frequency of the signal, or by setting a duty cycle of the signal to a predetermined duty cycle as examples. In this way, the incremental data replicates the error indication provided in the PWM signal. 
     In some embodiments in which the incremental data communicates a direction of movement of the target  514 , a detected error can be communicated in a different fashion than how direction is communicated. For example, in embodiments in which target direction is indicated by pulse width (e.g., as shown in  FIG. 2A ), detection of an error can be communicated by a change of a signal level of the incremental data. Alternatively, in embodiments in which target direction is indicated by different incremental data signal levels, presence of an error can be communicated by different pulse widths of the incremental data. 
     While the sensor  510  may be provided in the illustrated form of an IC with an analog front end portion and a digital portion, it will be appreciated that the particular delineation of which circuit functions are implemented in an analog fashion or with digital circuitry and signals can be varied. Further, some of the illustrated circuit functions can be implemented on an interface IC and other circuitry and functionality can be implemented on separate circuits (e.g., additional substrates within the same integrated circuit package, or additional integrated circuit packages, and/or on circuit boards). 
     Referring to  FIG. 6 , a sensor system  600  including an inductive position sensor interface IC  610  can be the same as or similar to IC  104   a  of  FIG. 1  and/or IC  510  of  FIG. 5  and can implement one or more of the above-described schemes for transmitting absolute and incremental data between the IC  610  and a control unit (not shown in  FIG. 6 , but which control unit can be the same as or similar to ECU  102  of  FIG. 1 ). 
     System  600  includes an oscillator  612 , a primary coil  618 , two secondary coils  620   a ,  620   b , and the interface IC  610 . Interface circuit  610  generates an oscillation signal for coupling to primary coil  618  and is coupled to receive secondary signals  622   a ,  622   b  from secondary coils  620   a ,  620   b , respectively, as shown. Secondary coils  620   a ,  620   b  are electromagnetically coupled to the primary coil  618  and mechanically coupled to a target  614  such that movement of the target causes position information to be encoded in the secondary signals  622   a ,  622   b  from coils  620   a ,  620   b  by amplitude modulation. In other words, the electromagnetic coupling between the primary coil  618  and secondary coils  620   a ,  620   b  is a function of the target position. In an example embodiment, the target  614  is a metallic, non-ferromagnetic object and the primary coil  618  induces eddy currents in the target, which eddy currents, in turn induce a signal in the secondary coils  620   a ,  620   b . As the target  614  moves (e.g., rotates), the coupling between the primary winding  618  and the secondary windings  620   a ,  620   b  changes, so as to thereby encode target position information by way of amplitude modulation of the secondary signals  622   a ,  622   b . It will be appreciated that various mechanical configurations for the target  614  and pickup coils  620   a ,  620   b  are possible. 
     The oscillator  612  may take the form of the illustrated resonant circuit (e.g., an LC tank circuit including capacitors and primary coil  618 ) or other oscillation circuits. Secondary windings  620   a ,  620   b  can be designed to have a predetermined phase relationship with respect to each other in order to suit a particular application. In the example embodiment, secondary windings  620   a ,  620   b  are designed to generate respective secondary signals in quadrature (i.e., having a nominal ninety-degree phase shift with respect to each other). With this arrangement, the system  600  can generate quadrature sine and cosine output signals that can be used to determine target speed, direction, and/or angle. 
     Interface IC  610  can include two signal paths, or channels (e.g., an analog, digital or mixed signal path) each coupled to receive a secondary signal  622   a ,  622   b  from a respective secondary winding  620   a ,  620   b . Each signal path can include a front end amplifier and EMI filter  624   a ,  624   b  and an analog-to-digital converter (ADC)  626   a ,  626   b , as shown. ADCs  626   a ,  626   b  can be configured to sample the respective secondary signal (e.g., by integration over sample periods) and convert the integrated signal into a respective digital signal  628   a ,  628   b.    
     A processor  630  is coupled to receive digital signals  628   a ,  628   b  and is configured to calculate an angle and/or speed of motion (e.g., rotation) of the target  614 . In embodiments, target angle can be computed using a CORDIC method and target speed can be computed as the derivative of target angle. For example, using consecutive angle values in time, speed is proportional to (angle_1−angle_0)/delta_time]. 
     Processor  630  may implement various signal conditioning and compensation of possible errors due to coils-target alignments and system design. For example, amplitude and offset adjustment may be provided. In general, signal amplitudes will be affected by the current flowing through the primary coil  618  and the distance between the coil and the target. Temperature may also affect signal amplitudes and offsets. Thus, processor  630  can be coupled to receive temperature information from a temperature sensor (not shown) and can operate to automatically track and compensate signal amplitudes and offsets. Harmonic compensation can be performed using correction parameters stored in EEPROM  634  in order to thereby remove undesirable harmonics that could adversely affect position sensing. 
     IC output signals  650  can be provided in one or more of various signal formats for coupling to external circuits and systems such as an ECU (not shown). Example output signal formats include PWM, SENT, ABI, or SPI to name a few. For example, IC  610  can include four output connections  650  usable for the various output formats as shown. For example, according to a SPI output signal format, output connections  650  can include a MISO (Master In Slave Out) line, a MOSI (Master OUT Slave IN) line, a SCLK (Serial Clock) line, and a CSN (Chip Slave select) line. In an ABI output signal mode, active output connections  650  can include A, B, and I signal lines. In a SENT output signal mode, active output connections  650  can include a SENT line with incremental data communicated on the same line as the absolute SENT data or else on a separate dedicated incremental line. And in a PWM mode, active output connections  650  can include a PWM line with incremental data communicated on the same line as the absolute PWM signal or else on a separate dedicated line. 
     The selection of interface output signal type (i.e., output mode) can be based on user-programmable parameters stored in EEPROM  634 . It will be appreciated that other output signal information such as speed and direction and other output signal formats are possible. 
     Interface  610  can be provided in the form of an integrated circuit (IC) including one or more semiconductor die and can receive power V SUPPLY    646  for coupling to an on-chip regulator  632  and can have a ground connection  648 . EEPROM  634  can store operating values and parameters, such as output signal format, gain and offset correction coefficients, and harmonic correction parameters as examples. 
     Having described preferred embodiments, which serve to illustrate various concepts, structures and techniques, which are the subject of this disclosure, it will now become apparent to those of ordinary skill in the art that other embodiments incorporating these concepts, structures and techniques may be used. 
     Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Various elements, which are described in the context of a single embodiment, may also be provided separately or in any suitable subcombination. Other embodiments not specifically described herein are also within the scope of the following claims.