Abstract:
A system includes a current sensor to receive an input signal based on a sense current provided to load circuitry. The current sensor is configurable to generate an output signal from the input signal based, at least in part, on one or more configurable characteristics of the current sensor. The system also includes a processing element to compare the output signal from the current sensor to one or more programmable parameters. The processing element is configurable to direct a current controller to regulate the sense current provided to the load circuitry according to the comparison, and is further configurable to set a configurable parameter associated with the current sense amplifier.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional application Ser. No. 12/238,383 filed Sep. 25, 2008 now U.S. Pat. No. 7,898,299 issued Mar. 1, 2011, the contents of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to electronic circuits, and more particularly to current sense amplifiers. 
     BACKGROUND 
     Many electronic systems include load circuitry that requires a regulated flow of current to operate properly. In order to control the current flow to the load circuitry, these electronic systems typically also include a current measurement device to measure the current flow to the load circuitry and a current control device to control or regulate current flow to the load circuitry. Thus, the current measurement device measures the current being provided to the load circuitry, the measurement is fed back to the current control device for adjustment of the current being provided to the load circuitry. 
     High-side current sense amplifiers are one common type of current measurement device utilized by the electronic systems. These high-side current sense amplifiers typically operate to sense a voltage difference across a high-side sense resistor that is coupled with a load circuitry. High-side current sense amplifiers can be constructed or configured to trade-off various performance options, such as gain accuracy and operating frequency or bandwidth. 
     SUMMARY 
     According to an embodiment, a system includes a current sense amplifier to receive an input voltage based on a sense current provided to load circuitry for operation. The current sense amplifier is configured to generate an output voltage from the input voltage based, at least in part, on one or more reconfigurable characteristics of the current sense amplifier. The system also includes a microcontroller to compare the output voltage from the current sense amplifier to one or more programmable thresholds. The microcontroller is configured to direct a current controller to regulate the sense current provided to the load circuitry according to the comparison. 
     According to an embodiment, a method comprising receiving an input voltage based on a sense current provided to load circuitry for operation, generating an output voltage from the input voltage based, at least in part, on one or more reconfigurable characteristics of a current sense amplifier, comparing the output voltage from the current sense amplifier to one or more programmable thresholds, and regulating the sense current provided to the load circuitry according to the comparing. 
     According to an embodiment, an apparatus comprising a first amplification circuit to receive an input voltage that corresponds to a current flowing through a sense resistor to load circuitry. The first amplification circuit is configured to amplify the input voltage according to one or more adjustable characteristics that are configurable by a microcontroller. The apparatus further comprising a second amplification circuit to generate an output voltage by amplifying the input voltage from the first amplification circuit according to one or more adjustable characteristics that are configurable by the microcontroller. The microcontroller utilizes the output voltage to regulate current provided to the load circuitry. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention may be best understood by reading the disclosure with reference to the drawings. 
         FIG. 1  is a block diagram of an example electronic system including a reconfigurable current sense amplifier according to embodiments of the invention. 
         FIG. 2  is a block diagram of an example reconfigurable current sense amplifier according to embodiments of the invention. 
         FIGS. 3A-3B  are diagrams illustrating operational embodiments of electronic system and the reconfigurable current sense amplifier shown in  FIGS. 1 and 2 . 
         FIG. 4  is a block diagram of an example reconfigurable current sense amplifier with self powering functionality according to embodiments of the invention. 
         FIG. 5  is a block diagram of an example reconfigurable current sense amplifier with a cross protection circuit according to embodiments of the invention. 
         FIG. 6  is an example operational flowchart for the electronic system as shown in  FIGS. 1-5 . 
     
    
    
     DETAILED DESCRIPTION 
     A programmable system on a chip (PSOC) or other electronic system can control the operation of various load circuits, such as light-emitting diode (LED) arrays or other current-driven circuits. Since these load circuits often have differing operational requirements, such as gain accuracy and operating frequency or bandwidth tradeoffs, the programmable system on a chip includes at least one reconfigurable current sense amplifier to ensure the programmable system on a chip can accommodate the various load circuits. Embodiments are shown and described below in greater detail. 
       FIG. 1  is a block diagram of an example electronic system  100  including a reconfigurable current sense amplifier  200  according to embodiments of the invention. Referring to  FIG. 1 , the electronic system  100  generates and regulates a sense current  114  that powers load circuitry  120 . The load circuitry  120  can be any current-driven device, such as a light-emitting diode (LED) array, control circuitry, or other load device that includes inductive and/or resistive electronic components. Although  FIG. 1  shows the load circuitry  120  as forming a part of the electronic system  100 , in some embodiments, the load circuitry  120  can be located externally to the electronic system  100 . 
     The electronic system  100  includes a sense resistor  110  coupled in series with the load circuitry  120 . The sense resistor  110  can receive a power supply voltage  102  and induce the sense current  114  to be provided to the load circuitry  120 . The electronic system  100  includes a current controller  130  to adjust the magnitude of the sense current  114  that is driven through a sense resistor  110 . In some embodiments, the current controller  130  includes a field effect transistor (FET), such as an N-type FET or other device that can regulate or control current flow through the load circuitry  120 . Thus, the combination of the sense resistor  110  and the current controller  130  can dictate the magnitude of the sense current  114  provided to the load circuitry  120 . 
     The electronic system  100  includes a reconfigurable current sense amplifier  200  to detect a sense voltage  112  or input voltage across the sense resistor  110 . The sense voltage  112  corresponds to the magnitude of sense current  114  generated by the current controller  130 , the sense resistor  110 , and the power supply voltage  102 . In some embodiments, the reconfigurable current sense amplifier  200  can receive the sense voltage  112  as a pair of inputs, one corresponding to the node of the sense resistor  110  coupled to the power supply voltage  102  and the other corresponding to the node of the sense resistor  110  coupled to the load circuitry  120 . 
     The reconfigurable current sense amplifier  200  can amplify the sense voltage  112  to generate an output voltage  205  according to one or more adjustable characteristics. For instance, the reconfigurable current sense amplifier  200  has an adjustable amplification gain, an adjustable input offset, and adjustable bandwidth compensation. Embodiments of the reconfigurable current sense amplifier  200  and these adjustable characteristics will be described below in greater detail. 
     The electronic system  100  includes a microcontroller  140  to control operations in the electronic system  100 . The microcontroller  140  can be a processor, microprocessor, or other controlling device, and in some embodiments, can be implemented in firmware or as a discrete set of hardware elements. Although not shown in  FIG. 1 , the microcontroller  140  can be coupled to a computer or machine readable medium or other memory device that includes instructions, when executed by the microcontroller  140 , can cause the microcontroller  124  to perform various functions or operations. 
     The microcontroller  140  can receive the output voltage  205  from the reconfigurable current sense amplifier  200  and generate current control signals  146  for transmission to the current controller  130  responsive to the output voltage  205 . The current control signals  146  can activate or deactivate the current controller  130  to drive the sense current  114 . In some embodiments, the microcontroller  140  can compare the output voltage  205  to one or more programmable thresholds to determine which current control signals  146  to provide to the current controller  130 . 
     The microcontroller  140  can generate configuration signals  142 , which direct configuration of adjustable characteristics in the reconfigurable current sense amplifier  200 . In some embodiments, the reconfigurable current sense amplifier  200  can have register electronically trimmable components that are reconfigured according to the configuration signals  142 . 
     The electronic system  100  includes a reference current generator  150  to provide reference currents  155  to the reconfigurable current sense amplifier  200 , e.g., in response to reference controller signals  144  from the microcontroller  150 . These reference currents  155  can be used to help power the reconfigurable current sense amplifier  200 , as will be shown and described below in greater detail. 
       FIG. 2  is a block diagram of an example reconfigurable current sense amplifier  200  according to embodiments of the invention. Referring to  FIG. 2 , the reconfigurable current sense amplifier  200  can include multiple stages, such as a first current sense amplifier stage  210  and a second current sense amplifier state  220 . The first current sense amplifier stage  210  is coupled to the sense resistor  110  to receive the sense voltage  112 , for example, on a pair of input lines. In some embodiments, the first current sense amplifier stage  210  receives two voltage inputs from the sense resistor  110 , where the voltage difference between the two voltage inputs is the sense voltage  112 . 
     The first current sense amplifier stage  210  can include a first resistor RP  211  coupled between a higher voltage side of the sense resistor  110  and an operational amplifier  212 . The lower voltage side of the sense resistor  110  can be coupled to another terminal of the operational amplifier  212 . In some embodiments, an adjustable input offset  213  can be coupled between the lower voltage side of the sense resistor  110  and the other terminal of the operational amplifier  212 . 
     The first current sense amplifier stage  210  can include a transistor  214 , such as a PMOS transistor, that when activated by an output of the operational amplifier  212 , generate a stage one output. The first current sense amplifier stage  210  also include a variable resistor RL  215  that is coupled to the stage one output and a ground. 
     The configuration of the first current sense amplifier stage  210  allows the sense voltage  112  detected across the sense resistor  110  to be amplified according to Equation 1. 
                     V   StageOneOut     =         R   L       R   P       ⁢     V   Sense               Equation   ⁢           ⁢   1               
Thus, the first current sense amplifier stage  210  amplifies the sense voltage  112  input into the system according a ratio between the two resistors, RP  211  and RL  213 , in the first current sense amplifier stage  210 .
 
     In some embodiments, the microcontroller  140  can provide configuration signals  142  to the reconfigurable current sense amplifier  200  that adjust the stage one output. For instance, the configuration signals  142  can adjust the resistance value of the variable resistor RL  215 , which may directly modify the amplification of the sense voltage  112 , as the resistance ratio shown in Equation 1 may change. The configuration signals  142  can also adjust the input offset  213  to alter the difference between the input voltages that are provided to the operational amplifier  212 , thus effectively changing the value of the sense voltage  112  that is amplified by the first current sense amplifier stage  210 . 
     The second current sense amplifier stage  220  includes an operational amplifier  222  that receives the stage one output at one terminal. The output of the operational amplifier  222  is coupled to multiple resistors, RX  223  and RY  224 , arranged in series. A node between the two resistors RX  223  and RY  224  is coupled as a feedback to the other terminal of the operational amplifier  222 . In some embodiments, an input offset  225  can be coupled between the node between the two resistors RX  223  and RY  224  and the other terminal of the operational amplifier  222 . 
     The configuration of the second current sense amplifier stage  220  allows the stage one output to be amplified according to Equation 2. 
     
       
         
           
             
               
                 
                   
                     V 
                     Output 
                   
                   = 
                   
                     
                       ( 
                       
                         1 
                         + 
                         
                           
                             R 
                             X 
                           
                           
                             R 
                             Y 
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       V 
                       StageOneOut 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
             
           
         
       
     
     Thus, the second current sense amplifier stage  220  amplifies the stage one output according a ratio between the two resistors, RX  223  and RY  224 , in the second current sense amplifier stage  210 . In some embodiments, the microcontroller  140  can provide configuration signals  142  to the reconfigurable current sense amplifier  200  that adjust the characteristics of the second current sense amplifier stage  220  to vary the output voltage  205 . For instance, the configuration signals  142  can adjust the resistance value of the variable resistor RY  2234  which may directly modify the amplification of the stage one output, as the resistance ratio shown in Equation 2 may change. The configuration signals  142  can also adjust the input offset  225  to alter the difference between the input voltages that are provided to the operational amplifier  222 . 
     Thus, the output voltage  205  of the reconfigurable current sense amplifier  200  can be expressed according to Equation 3. 
     
       
         
           
             
               
                 
                   
                     V 
                     Output 
                   
                   = 
                   
                     
                       ( 
                       
                         1 
                         + 
                         
                           
                             R 
                             X 
                           
                           
                             R 
                             Y 
                           
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       ( 
                       
                         
                           R 
                           L 
                         
                         
                           R 
                           P 
                         
                       
                       ) 
                     
                     ⁢ 
                     
                       V 
                       Sense 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
               
             
           
         
       
     
     The second current sense amplifier stage  220  can also include a bandwidth compensation circuit  221  that is coupled between the stage one output and the operational amplifier  222 . The bandwidth compensation circuit  221  can dampen the effect of noise in the power supply voltage  102  that is amplified in the first current sense amplification stage  210 . By dampening the noise in the power supply voltage, the reconfigurable current sense amplifier  200  can optimize a Power Supply Rejection Ratio (PSRR) and limit subsequent swings in the sense current  114  due to the power supply noise. In some embodiments, the bandwidth compensation circuit  221  can include a variable capacitor, for example, that is adjustable according to the configuration signals  142  from the micro controller  140 . 
     The reconfigurable current sense amplifier  200  can include a bypass circuit  230  that can optionally bypass the second current sense amplifier stage  220 . In some embodiments, the configuration signals  142  from the microcontroller  140  can control the operation of the bypass circuit  230 . Thus, when the bypass circuit  230  is activated to bypass the second current sense amplifier stage  220 , the stage one output becomes the output voltage  205 . In some embodiments, the bypass circuit  230  can be activated to bypass the second current sense amplifier stage  220  during lower frequency operation of the electronic system, while during higher frequency operation the bypass circuit  230  can be set to have the second stage output become the output voltage  205 . 
       FIGS. 3A-3B  are diagrams illustrating operational embodiments of electronic system  100  and the reconfigurable current sense amplifier  200  shown in  FIGS. 1 and 2 . Referring to  FIGS. 3A and 3B , the diagram  300 A discloses a lower frequency operation for the electronic system  100 , and diagram  300 B discloses a higher frequency operation for the electronic system  100 . As discussed above, in  FIGS. 1 and 2 , the microcontroller  140  directs the current controller  130  to activate and deactivate based, at least in part, on the output voltage  205  received from the reconfigurable current sense amplifier  200 . The microcontroller  140  compares the output voltage  205  to one or more thresholds, for example, an upper threshold and a lower threshold, to determine when to activate or deactivate the current controller  130 . 
     When the current controller  130  is activated, for example, responsive to current control signals  146  from the microcontroller  140 , the sense current  114  (and corresponding sense voltage  112  and output voltage  205 ) increases over time. The microcontroller  140  can compare the output voltage  205  to the upper threshold to determine when to direct the current controller  130  to deactivate. When the current controller  130  is deactivated, for example, responsive to current control signals  146  from the microcontroller  140 , the sense current  114  (and corresponding sense voltage  112  and output voltage  205 ) decreases over time. The microcontroller  140  can compare the output voltage  205  to the lower threshold to determine when to direct the current controller  130  to activate again. The activation and deactivation of the current controller  130  generates an oscillation of the sense current  114 , sense voltage  112 , and the output voltage  205 , which is known as the operational frequency of the electronic system  100 . 
     The operational frequency of the electronic system  100  can be modified by the microcontroller  140  by adjusting the thresholds and/or by reconfiguring the current sense amplifier  200 . For instance, when the thresholds are positioned closer together, less time can required before the current controller  130  is activated or deactivated, thus increasing the operational frequency. Similarly, when the thresholds are positioned farther apart, more time can required before the current controller  130  is activated or deactivated, thus increasing the operational frequency. 
     Reconfiguring the current sense amplifier  200  to adjust the gain can also modify the operational frequency of the electronic system  100 . Since the slope of the output voltage  205 , when the current controller  130  is activated, is at least in part dictated by the gain of the reconfigurable current sense amplifier  200 , any change in slope can also prompt activation or deactivation of the current controller  130 . As shown, in  FIG. 3B , the gain of the reconfigurable current sense amplifier  200  was increased, which also increased the positive slope of the output voltage  205  over time, and thus increased the operational frequency of the electronic system  100 . 
     Other adjustments to the reconfigurable current sense amplifier  200 , such as modifying the input offsets  213  and  225  into the operational amplifiers  212  and  222 , respectively, activating the bandwidth compensation circuit  221 , and/or bypassing the second current sense amplifier stage  220 , can also affect the waveforms illustrated in  FIGS. 3A and 3B . For instance, adjustment to the input offset can alter the DC level of the waveform by raising or lowering the waveform along the Y-axis. Input offset adjustment can also alter the duty cycle of the waveform, allowing system designers or programmers to maximize power efficiency by limiting the time that the current controller  130  is activated. 
       FIG. 4  is a block diagram of an example reconfigurable current sense amplifier  200  with self powering functionality according to embodiments of the invention. Referring to  FIG. 4 , the reconfigurable current sense amplifier  200  can include circuitry that powers the operational amplifiers  212  and  222  from the high node of the sense voltage  112 , i.e., utilizes the high node of the sense voltage  112  as an elevated power supply  408  and generates an elevated analog ground  406  from the elevated power supply  408 . 
     The reconfigurable current sense amplifier  200  includes a power resistor  410  that is coupled to receive the elevated power supply  408 . A current source  420  can draw current through the power resistor  410  to induce a voltage drop across the power resistor  410 . In some embodiments, a voltage drop across the power resistor  410  is approximately equal to 6V. This voltage drop lowers the voltage level of the elevated power supply for use as an elevated analog ground  406 . 
     The reconfigurable current sense amplifier  200  includes a first transistor  402  to generate the elevated analog ground  406  responsive to receiving the elevated power supply with the voltage drop at its gate region. In some embodiments, the first transistor  402  can be a PMOS transistor. The reconfigurable current sense amplifier  200  includes a second transistor  404  can be coupled between the first transistor  402  and a ground, with its gate region configured to receive an enable signal  401 . In some embodiments, the second transistor  404  can be a NMOS transistor. When the enable signal  201  is activated, the first transistor  402  can provide the elevated analog ground  406  to the operational amplifier  212 . 
       FIG. 5  is a block diagram of an example reconfigurable current sense amplifier  200  with a cross protection circuit  510  according to embodiments of the invention. Referring to  FIG. 5 , the reconfigurable current sense amplifier  200  includes a cross protection circuit  510  to help ensure a voltage difference received by the operational amplifier  212  at its two input terminals does not exceed a predetermined level. 
     The cross protection circuit  510  can include resistors coupled in series with the two input lines coupling to the input terminals of the operational amplifier  212 . The cross protection circuit  510  can also include diodes that cross-connect between the two input lines. During normal operation the diodes remain inactive, i.e., do not pass current or voltage to the other input line that is sufficient enough to effect operation. When the voltage difference between the two input lines exceeds a predetermined level, at least one of the diodes activates, to substantially equalize the voltage on the two input lines. The cross protection circuit  510  ensures that the voltage difference received by the operational amplifier  212  at its two input terminals is sufficiently large to affect the operation of the operational amplifier  212 . Thus, the cross protection circuit  510  improves the robustness of the reconfigurable current sense amplifier  200  during its operational life. 
       FIG. 6  is an example operational flowchart for the electronic system  100  as shown in  FIGS. 1-5 . Referring to  FIG. 6 , at a block  610 , the electronic system  100  receives an input voltage or sense voltage  112  based on a sense current  114  provided to load circuitry  120 . 
     A sense resistor  110  can receive a power supply voltage  102  and induce the sense current  114  to be provided to the load circuitry  120 . The electronic system  100  includes a current controller  130  to adjust the magnitude of the sense current  114  that is driven through a sense resistor  110 . Thus, the combination of the sense resistor  110  and the current controller  130  can dictate the magnitude of the sense current  114  provided to the load circuitry  120 . 
     The reconfigurable current sense amplifier  200  can detect the sense voltage  112  or input voltage across the sense resistor  110 . The sense voltage  112  corresponds to the magnitude of sense current  114  generated by the current controller  130 , the sense resistor  110 , and the power supply voltage  102 . In some embodiments, the reconfigurable current sense amplifier  200  can receive the sense voltage  112  as a pair of inputs, one corresponding to the node of the sense resistor  110  coupled to the power supply voltage  102  and the other corresponding to the node of the sense resistor  110  coupled to the load circuitry  120 . 
     In a next block  620 , the electronic system  100  generates an output voltage  205  from the input voltage  112  based, at least in part, on one or more reconfigurable characteristics of a current sense amplifier  200 . 
     In some embodiments, the electronic system  100  can set an adjustable gain associated with the current sense amplifier  200 , and amplify the input voltage  112  according to the adjustable gain to generate the output voltage  205 . The electronic system  100  can also set an input voltage offset associated with the current sense amplifier, and amplify the input voltage according to the input voltage offset to generate the output voltage. 
     In the next blocks  630  and  640 , the electronic system  100  compares the output voltage  205  from the reconfigurable current sense amplifier  200  to one or more programmable thresholds, and regulates the sense current  114  provided to the load circuitry  120  according to the comparing. 
     In some embodiments, the electronic system  100  can dictate an operational frequency associated with the sense current  114  based, at least in part, on an upper threshold and a lower threshold. For instance, the microcontroller  140  can compare the output voltage  205  to the upper threshold, and can cease driving the sense current  114  through the load circuitry  140  when the output voltage  205  meets or exceeds the upper threshold. In some embodiments, the microcontroller  140  can prompt the current controller  130  to deactivate, and thus cease driving the sense current  114 . 
     The microcontroller  140  can also compare the output voltage  205  to the lower threshold, and can drive the sense current  114  through the load circuitry  140  when the output voltage  205  meets or exceeds the lower threshold. In some embodiments, the microcontroller  140  can prompt the current controller  130  to activate, and thus drive the sense current  114 . The switching between the activation and deactivation of the current controller  130  over time can cause the sense current  114 , the sense voltage  112 , and the output voltage  205  to oscillate, defining the operating frequency of the electronic system  100 . 
     One of skill in the art will recognize that the concepts taught herein can be tailored to a particular application in many other advantageous ways. In particular, those skilled in the art will recognize that the illustrated embodiments are but one of many alternative implementations that will become apparent upon reading this disclosure. 
     The preceding embodiments are exemplary. Although the specification may refer to “an”, “one”, “another”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment.