Patent Publication Number: US-2023155504-A1

Title: Multi-Phase Power Converter with External Driver

Description:
PRIORITY INFORMATION 
     The present application is a continuation of U.S. Appl. No. 17/343,418, entitled “Multi-Phase Power Converter with External Driver,” filed Jun. 9, 2021, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Technical Field 
     This disclosure relates to power management in computer systems, and, more particularly, to voltage regulator circuit operation. 
     Description of the Related Art 
     Modern computer systems may include multiple circuit blocks designed to perform various functions. For example, such circuit blocks may include processors or processor cores configured to execute software or program instructions. Additionally, the circuit blocks may include memory circuits, mixed-signal or analog circuits, and the like. 
     In some computer systems, the circuit blocks may be designed to operate using different power supply voltage levels. For example, in some computer systems, power management circuits (also referred to as “power management units”) may generate and monitor various power supply signals. 
     Power management circuits often include one or more power converter circuits configured to generate regulator voltage levels on respective power supply signal lines using a voltage level of an input power supply signal. Such converter circuits may employ multiple reactive circuit elements, such as inductors, capacitors, and the like. 
     SUMMARY OF THE EMBODIMENTS 
     Various embodiments for generating a voltage level on a regulated power supply node are disclosed. Broadly speaking, a power converter system includes a primary control circuit and multiple phase circuits included on a particular integrated circuit. The primary control circuit is configured to selectively activate the multiple phase circuits. A first phase circuit of the multiple phase circuits is configured to activate, using a first phase clock signal, a first driver circuit coupled to a regulated power supply node via a first inductor, where the first driver circuit is included on the particular integrated circuit and is configured to source a first current to the regulated power supply node during a first on-time period. A second phase circuit of the multiple phase circuits is configured to activate, using a second phase clock signal, a second driver circuit coupled to the regulated power supply node via a second inductor, where the second driver circuit is included on a different integrated circuit and is configured to source a second current to the regulated power supply node during a second on-time period. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a block diagram of an embodiment of a power converter system for a computer system. 
         FIG.  2    illustrates a block diagram of another embodiment of a power converter system. 
         FIG.  3    illustrates a block diagram of an embodiment of an internal/external phase circuit for a power converter circuit. 
         FIG.  4    illustrates a block diagram of an embodiment of an internal driver circuit. 
         FIG.  5    illustrates a block diagram of an embodiment of an external phase circuit for a power converter circuit. 
         FIG.  6    illustrates a block diagram of an embodiment of an external driver circuit for a power converter circuit. 
         FIG.  7    illustrates a block diagram of a control circuit for a power converter phase circuit. 
         FIG.  8    illustrates a block diagram of a primary control circuit for a power converter circuit. 
         FIG.  9    illustrates a block diagram of a power management system that employs external phase circuits. 
         FIG.  10    illustrates a block diagram of a phase circuit for use with a power management circuit. 
         FIG.  11    illustrates a block diagram of a control circuit for use with a power management circuit. 
         FIG.  12    illustrates a block diagram of a power management system with shared phase circuits. 
         FIG.  13    illustrates a flow diagram that depicts an embodiment of a method for operating a power converter system. 
         FIG.  14    illustrates a flow diagram that depicts an embodiment of a method for operating a power management circuit. 
         FIG.  15    is a block diagram of a system-on-a-chip. 
         FIG.  16    is a block diagram of an embodiment of a computer system. 
         FIG.  17    illustrates an example of a non-transitory computer-readable storage medium that stores circuit design information. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Computer systems may include multiple circuit blocks configured to perform specific functions. Such circuit blocks may be fabricated on a common substrate and may employ different power supply voltage levels. Power management units (commonly referred to as “PMUs”) may include multiple power converter or voltage regulator circuits configured to generate regulated voltage levels for various power supply signals. Such voltage regulator circuits may employ both passive circuit elements (e.g., inductors, capacitors, etc.) as well as active circuit elements (e.g., transistors, diodes, etc.). 
     Different types of voltage regulator circuits may be employed based on power requirements of load circuits, available circuit area, and the like. One type of commonly used voltage regulator circuit is a buck converter circuit. Such converter circuits include multiple switches (also referred to as “power switches”) and a switch node that is coupled to a regulated power supply node via an inductor. One switch is coupled between an input power supply node and the switch node, and is referred to as the “high-side switch.” Another switch is coupled between the switch node and a ground supply node, and is referred to as the “low-side switch.” 
     When the high-side switch is closed (referred to as “on-time”), energy is applied to the inductor, resulting in the current through the inductor increasing. During this time, the inductor stores energy in the form of a magnetic field. When the high-side switch is opened and the low-side switch is closed (referred to as “off-time”), energy is no longer being applied to the inductor, and the voltage across the inductor reverses, which results in the inductor functioning as a current source, with the energy stored in the inductor’s magnetic field supporting the current flowing into the load. The process of closing and opening the high-side and low-side switches is performed periodically to maintain a desired voltage level on the power supply node. 
     Power converter circuits may employ different regulation modes to determine periodicity and duration of on-times and off-times. As used herein, a regulation mode refers to a particular method of detecting operating conditions to determine frequencies and durations of on-times and off-times employed by a power converter circuit. For example, a power converter may detect a maximum current flowing through its inductor to determine an end of an on-time period. This type of regulation mode is referred to as a “peak-current regulation mode.” Alternatively, a power converter may detect a minimum current flowing through its inductor to determine an end of an off-time period. This type of regulation mode is referred to as a “valley-current regulation mode.” 
     As the level of integration increases, power converters need to supply increasing amounts of current to load circuits. For example, in some cases, power converters need to be able to supply 100A or more to load circuits. Existing power converter solutions are limited by thermal budgets and packaging requirements. As a result, the scalability of current power converter designs is limited and inefficient for higher current applications. Moreover, the efficiency of power converter circuits at smaller loads must be maintained, and the design of power converter circuits must be flexible to allow for changes in current requirements at late stages in the design process. 
     Techniques described in the present disclosure allow for a power converter circuit that employs a combination of external phase and driver circuits that may be located on different integrated circuits. Such external phase and driver circuits may be fabricated with different physical characteristics allowing the use of higher input voltages, thereby allowing the power converter to more easily support higher current demands. With the external phase and driver circuits being located on different integrated circuits, heat generated by the power converter circuit is not located on a single integrated circuit, improving thermal management. Moreover, additional external phase and driver circuits can be added later in the design process to more easily adapt to changes in load current as a computer system design evolves. 
     Turning to  FIG.  1   , a block diagram of a power converter system is depicted. As illustrated, power converter system  100  includes primary control circuit  101 , phase circuit  102 , phase circuit  103 , and driver circuit  105 . In various embodiments, primary control circuit  101 , and phase circuits  102  and  103  are located on integrated circuit  109 , while driver circuit  105  is located on integrated circuit  110 . It is noted that although only two phase circuits are depicted as being included on integrated circuit  109 , in other embodiments, any suitable number of phase circuits may be included on integrated circuit  109 . 
     Primary control circuit  101  is configured to selectively activate either of phase circuits  102  and  103 . As described below, primary control circuit  101  may be configured to generate phase clock signals  111 , along with other control, reference, and enable signals (all not shown) used by phases circuits  102  and  103 . In various embodiments, primary control circuit  101  may be configured to support additional phase circuits. The number of phase circuits managed by primary control circuit  101  may be controlled by control bits that are stored in a register, one-time programmable memory, or other suitable storage location. 
     As used herein, when a signal is activated, it is set to a logic or voltage level that activates a load circuit or device. The logic level may be either a high logic level or a low logic level depending on the load circuit. For example, an active state of a signal coupled to a p-channel MOSFET is a low logic level (referred to as an “active low signal”), while an active state of a signal coupled to an n-channel MOSFET is a high logic level (referred to as an “active high signal”). 
     Phase circuit  102  includes driver circuit  104  and is configured to activate, using a first phase clock signal of phase clock signals  111 , driver circuit  104 , which is coupled to regulated power supply node  108  via inductor  106 . Driver circuit  104  is configured to source current  112  to regulated power supply node  108  during a first on-time period. 
     Phase circuit  103  is configured to activate, using a second phase clock signal of phase clock signals  111 , driver circuit  105 , which is coupled to regulated power supply node  108  via inductor  107 . Driver circuit  105  is configured to source current  113  to regulated power supply node  108  during a second on-time period. It is noted that the first on-time period and the second on-time period may be different or they may overlap. The respective timings and durations of the first and second on-time periods may be based on currents  112  and  113 , the first and second phase clocks, as well as the voltage level of regulated power supply node  108 . 
     Inductors  106  and  107  may, in various embodiments, be located on integrated circuit  109 . Alternatively, inductors  106  and  107  may be located on integrated circuit  110 , or an integrated circuit different from either integrated circuit  109  or integrated circuit  110 . In various embodiments, inductors  106  and  107  may be implemented as chip inductors coupled to integrated circuits  109  and  110 . In other embodiments, inductors  106  and  107   may be fabricated as planar spirals or other suitable structures on either of integrated circuit  109  or  110 . 
     In the embodiment of  FIG.  1   , driver circuit  105 , which is external to integrated circuit  109 , is controlled by phase circuit  103 . As illustrated, phase circuit  103  has no internal driver circuit and is configured to control only external driver circuits. In some cases, however, phase circuits, such as phase circuit  102 , which include internal driver circuits, may be configured to control external driver circuits as well. Another embodiment of a power converter system that includes a phase circuit capable of driving both internal and external driver circuits is depicted in  FIG.  2   . 
     As illustrated, power converter system  200  includes primary control circuit  101 , phase circuit  102 , phase circuit  201 , and driver circuit  105 . Primary control circuit  101 , phase circuit  102 , and driver circuit  105  are configured to operate in a similar fashion to what is described in the embodiment of  FIG.  1   . 
     Phase circuit  201  includes driver circuit  202  and is configured to activate, using a phase clock signal of phase clock signals  111 , driver circuit  105 , which is coupled to regulated power supply node  108  via inductor  106 . As described below, phase circuit  201  may disable driver circuit  202  based on a value of enable signal  203 . In various embodiments, the value of enable signal  203  may be set during initialization or as part of a power-up sequence. Alternatively, the value of enable signal  203  may be stored in a non-volatile memory circuit, a one-time programmable memory circuit, or any other suitable storage circuit. 
     It is noted the embodiment depicted in  FIG.  2    is merely an example. In other embodiments, additional phase circuits, including phase circuits without internal driver circuits, may be included on integrated circuit  109 . 
     As described above, different types of phase circuits may be employed in a power converter circuit. Some phase circuits may be dedicated for use with external driver circuits (referred to as “external phase circuits”), while other phase circuits may be used with both internal and external driver circuits (referred to as “internal/external phase circuits”). 
     A block diagram of an embodiment of an internal/external phase circuit is depicted in  FIG.  3   . As illustrated, internal/external phase circuit  300  includes control circuit  301 , internal driver circuit  302 , and buffer circuit  303 . In various embodiments, internal/external phase circuit  300  may correspond to phase circuit  102  as depicted in  FIG.  1   . 
     Control circuit  301  is configured to generate control signal  310  and control signal  311  using phase enable signal  307 , driver enable signal  308 , and reference voltage  309 . In some embodiments, phase enable signal  307  may be a phase clock signal whose frequency is used in determining a duration of an on-time or off-time associated with a driver circuit. Reference voltage  309  may, in various embodiments, be indicative of a desired voltage level for regulated power supply node  108 . 
     In various embodiments, control circuit  301  may be configured to generate control signal  310  for a particular value of driver enable signal  308 , and to generate control signal  311  for a different value of driver enable signal  308 . For example, in response to a determination that driver enable signal  308  is at a high logic level, control circuit  301  may activate control signal  311  based on the values of phase enable signal  307  and reference voltage  309 . 
     As described below, control circuit  301  may be configured to generate control signal  310  to determine the on-time and off-time of high-side and low-side switches in a driver circuit (e.g., internal driver circuit  302 ). Control circuit  301  may be configured to control the on-time and off-time according to pulse-width modulation or pulse-frequency modulation. In various embodiments, control circuit  301  may employ either peak-current regulation or valley-current regulation. 
     Control circuit  301  may be implemented using any suitable combination of combinatorial and sequential logic circuits. In various embodiments, control circuit  301  may include one or more comparator or amplifier circuits. 
     Internal driver circuit  302  is configured to drive output node  304  based on control signal  310 . In various embodiments, output node  304  may be coupled to an inductor (e.g., inductor  106 ), when driver enable signal  308  is set to a value to cause internal/external phase circuit  300  to operate using internal driver circuit  302  as opposed to an external driver circuit. As described below, internal driver circuit  302  may include multiple high-side switches that can couple output node  304  to power supply node  305 , allowing a current to flow from power supply node  305  through output node  304  into an inductor. Internal driver circuit  302  may also include multiple low-side switches that can couple output node  304  to a ground supply node, allowing the inductor to function as a current source as its magnetic field collapses. The number of high-side switches and low-side switches can vary based on operating mode. For example, when internal/external phase circuit  300  is operating as an internal phase circuit, internal driver circuit  302  may employ all available high-side and low-side switches, and when internal/external phase circuit  300  is operating as an external phase circuit, internal driver circuit  302  may all, or any suitable portion thereof, of the available high-side and low-side switches. 
     Buffer circuit  303  is coupled to power supply node  306 , and is configured to buffer control signal  311  and drive the signal onto output node  304 . It is noted that, in various embodiments, a voltage level of power supply node  306  is greater than a voltage level of power supply node  305 . In various embodiments, when buffer circuit  303  is inactive, it may enter a high output impedance state (referred to as “tri-state”) to avoid loading the output of internal driver circuit  302 . Buffer circuit  303  may, in some embodiments, be implemented as a non-inverting amplifier circuit, two inverter logic gates coupled in series, or any other suitable circuit. 
     Turning to  FIG.  4   , a block diagram of an internal driver circuit is depicted. As illustrated, internal driver circuit  400  includes gate control circuit  401 , buffer circuits  402 A-C, buffer circuits  403 A-C, and slices  414 A-C. Slice  414 A includes devices  404 A and  405 A, and slice  414 B includes devices  404 B and  405 B. In a similar fashion, slice  414 C includes devices  404 C and  405 C. In various embodiments, internal driver circuit  400  may correspond to internal driver circuit  302  as depicted in  FIG.  3   . 
     Gate control circuit  401  is configured to generate signals  410  and  411  using control signal  408  and enable signal  409 . In various embodiments, enable signal  409  may correspond to driver enable signal  308 , and control signal  408  may correspond to phase enable signal  307  as depicted in  FIG.  3   . It is noted that in various embodiments, different ones of signals  410  and  411  may be activated to activate different ones of slices  414 A-C. By adjusting the number of slices  414 A-C that are active, the strength with which output node  406  is driven can be adjusted, allowing internal driver circuit  400  to drive either an inductor or an external driver circuit. In some embodiments, gate control circuit  401  is configured to deactivate signals  410  and  411  in response to a determination that enable signal  409  is deactivated. 
     When enable signal  409  is active, gate control circuit  401  is configured to activate signals  410  and  411  based on control signal  408 . For example, gate control circuit  401  may be configured to activate particular ones of signals  410  and deactivate particular ones of signals  411  in response to a determination that control signal  408  is active. In some cases, gate control circuit  401  may be configured to activate one or more of signals  410  and deactivate one or more of signals  411  during an on-time of phase circuit (e.g., internal/external phase circuit  300 ). Gate control circuit  401  may be further configured to deactivate one or more of signals  410  and activate one or more of signals  411  during an off-time of the phase circuit. 
     To avoid shoot-through current from power supply node  305  to ground supply node  306  when devices  404 A-C and  405 A-C are both active, gate control circuit  401  may, in some embodiments, be configured to generate signals  410  and  411  such that particular ones of signals  410  and  411  are not active at the same time. In various embodiments, gate control circuit  401  may be implemented using any suitable combination of combinatorial and sequential logic circuits. 
     Buffer circuit  402 A is configured to generate signal  412 A using one of signals  410 , and buffer circuit  402 B is configured to generate signal  412 B using a different one of signals  410 . In a similar fashion, buffer circuit  402 C is configured to generate signal  412 C using a corresponding one of signals  410 . Buffer circuit  403 A is configured to generate signal  413 A using one of signals  411 , and buffer circuit  403 B is configured to generate signal  413 B using a different one of signals  411 . In a similar fashion, buffer circuit  403 C is configured to generate signal  413 C using a corresponding one of signals  411 . In some embodiments, buffer circuits  402 A-C and  403 A-C may provide additional drive, in order to drive the control terminals of devices  404 A-C and  405 A-C, respectively. Buffer circuits  402 A-C and  403 A-C may, in various embodiments, be implemented as non-inverting amplifier circuits, series-connected inverter gates, or any other suitable circuit. 
     Devices  404 A-C are coupled between power supply node  305  and output node  406 , and are controlled by corresponding ones of signals  412 A-C. For example, in response to a determination that signal  412 A is active, device  404 A is configured to couple power supply node  305  to output node  406 , allowing current to flow from power supply node  305  into output node  406 . It is noted that output node  406  may be coupled to an inductor (e.g., inductor  106 ), in which case devices  404 A-C may collectively function as a high-side switch for the inductor. Alternatively, output node  406  may be coupled to an external driver circuit, such as driver circuit  105 . In various embodiments, devices  404 A-C may be implemented as a p-channel metal-oxide semiconductor field-effect transistor (MOSFET), Fin field-effect transistor (FinFET), or a gate-all-around field-effect transistor (GAAFET). 
     Devices  405 A-C are coupled between output node  406  and ground supply node  306 , and are configured to couple output node  406  to ground supply node  306  based on corresponding ones of signals  413 A-C. When output node  406  is coupled to an inductor, devices  405 A-C collectively function as a low-side switch for the inductor, allowing the inductor to be de-magnetized during an off period. In various embodiments, device  405 A-C may be implemented as an n-channel MOSFETs, FinFETs, or GAAFETs. 
     As described above, some phase circuits do not include an internal driver circuit and are configured to drive an external driver circuit. A block diagram of an embodiment of such a phase circuit is depicted in  FIG.  5   . As illustrated, external phase circuit  500  includes control circuit  501  and buffer  502 . In various embodiments, external phase circuit  500  may correspond to phase circuit  103  as depicted in  FIG.  1   . 
     Control circuit  501  is configured to generate control signal  504  using phase enable signal  503 , and reference voltage  309 . In some embodiments, phase enable signal  503  may be a phase clock signal whose frequency is used in determining a duration of an on-time or off-time associated with a driver circuit. Reference voltage  309  may, in various embodiments, be indicative of a desired voltage level for regulated power supply node  108 . 
     As described below, control circuit  501  may be configured to generate control signal  504  to determine the on-time and off-time of high-side and low-side switches in a driver circuit (e.g., driver circuit  105 ). Control circuit  501  may be configured to control the on-time and off-time according to pulse-width modulation or pulse-frequency modulation. In various embodiments, control circuit  501  may employ either peak-current regulation or valley-current regulation. 
     Control circuit  501  may be implemented using any suitable combination of combinatorial and sequential logic circuits. In various embodiments, control circuit  501  may include one or more comparator or amplifier circuits. 
     Buffer circuit  502  is coupled to power supply node  306 , and is configured to buffer control signal  504  to generate buffered control signal  505 . It is noted that, in various embodiments, a voltage level of power supply node  306  is greater than a voltage level of power supply node  305 . Buffer circuit  502  may, in some embodiments, be implemented as a non-inverting amplifier circuit, two inverter logic gates coupled in series, or any other suitable circuit. 
     Turning to  FIG.  6   , a block diagram of an external driver circuit is depicted. As illustrated, internal driver circuit  600  includes logic circuit  601 , buffer circuit  602 , buffer circuit  603 , and devices  604  and  605 . In various embodiments, external driver circuit  600  may correspond to driver circuit  105  as depicted in  FIG.  1   . 
     Logic circuit  601  is configured to generate signals  610  and  611  using control signal  607 . In various embodiments, control signal  607  may correspond to one of phase clock signals  111  as depicted in  FIG.  1   . Logic circuit  601  is configured to activate signals  610  and  611  based on control signal  607 . For example, logic circuit  601  may be configured to activate signal  610  and deactivate signal  611  in response to a determination that control signal  607  is active. In some cases, logic circuit  601  may be configured to activate signal  610  and deactivate signal  611  during an on-time of phase circuit (e.g., phase circuit  103 ). Logic circuit  601  may be further configured to deactivate signal  610  and activate signal  611  during an off-time of the phase circuit. 
     To avoid shoot-through current from power supply node  608  to ground supply node  609  when devices  604  and  605  are both active, logic circuit  601  may, in some embodiments, be configured to generate signals  610  and  611  such that both signals are not active at the same time. In various embodiments, logic circuit  601  may be implemented using any suitable combination of combinatorial and sequential logic circuits. 
     Buffer circuit  602  is configured to generate signal  612  using signal  610 , and buffer circuit  603  is configured to generate signal  613  using signal  611 . In some embodiments, buffer circuits  602  and  603  may provide additional drive in order to drive the control terminals of devices  604  and  605 , respectively. Buffer circuits  602  and  603  may, in various embodiments, be implemented as non-inverting amplifier circuits, series connected inverter gates, or any other suitable circuit. 
     Device  604  is coupled between power supply node  608  and output node  606 , and is controlled by signal  612 . In response to a determination that signal  612  is active, device  604  is configured to couple power supply node  608  to output node  606 , allowing current to flow from power supply node  608  into output node  606 . It is noted that output node  606  may be coupled to an inductor (e.g., inductor  107 ), in which case device  604  may function as a high-side switch for the inductor. In various embodiments, device  604  may be implemented as a p-channel MOSFET, FinFET, or a GAAFET. 
     Device  605  is coupled between output node  606  and ground supply node  609 , and is configured to couple output node  606  to ground supply node  609  based on signal  613 . When output node  606  is coupled an inductor, device  605  functions as a low-side switch for the inductor, allowing the inductor to be de-magnetized during an off period. In various embodiments, device  605  may be implemented as an n-channel MOSFET, FinFET, or GAAFET. It is noted that devices  604  and  605  may have different physical characteristics (e.g., oxide thickness) than devices  404  and  405 , allowing devices  604  and  605  to operate with higher voltages than devices  404  and  405 . 
     Turning to  FIG.  7   , a block diagram of an embodiment of a control circuit is depicted. As illustrated, control circuit  700  includes latch circuit  702 , current sensor circuit  703 , error amplifier circuit  704 , slope compensation circuit  705 , and comparator circuit  706 . In various embodiments, control circuit  700  may correspond to control circuit  301  or control circuit  501 . 
     Latch circuit  702  is configured to deactivate control signal  717  using reset signal  712  and set signal  718 . In various embodiments, reset signal  712  may correspond to one of phase clock signals  111 . In some embodiments, latch circuit  702  is configured to activate control signal  717  in response to an activation of set signal  718 , and deactivate control signal  717  in response to an activation of reset signal  712 . In various embodiments, latch circuit  702  may be implemented as a set-reset (SR) latch circuit that includes any suitable combination of logic gates. 
     Current sensor circuit  703  is coupled to sensor node  707 , and is configured to generate inductor current  716 . Sensor node  707  may, in some embodiments be coupled to a switch node of a power converter circuit, or coupled to a terminal of a device in a driver circuit (e.g., driver circuit  105 ). In various embodiments, current sensor circuit  703  may measure a voltage drop across the device in the driver circuit and generate inductor current  716  using the measured voltage drop. Current sensor circuit  703  may include any suitable combination of reference and amplifier circuits. 
     Error amplifier circuit  704  is configured to generate demand current  714  using reference voltage  713  and a voltage level of regulated power supply node  108 . In various embodiments, error amplifier circuit  704  may be configured to generate demand current  714  such that a value of demand current  714  is proportional to a difference between reference voltage  713  and the voltage level of regulated power supply node  108 . Error amplifier circuit  704  may, in some embodiments, be implemented as a differential amplifier circuit, or any other suitable comparator circuit. 
     Slope compensation circuit  705  is configured to modify inductor current  716 . In various embodiments, slope compensation circuit  705  may be configured, in a process referred to as “slope compensation,” to combine a periodic current ramp with inductor current  716 . It is noted that slope compensation is used to improve the stability of a phase circuit (e.g., phase circuit  102 ) by increasing a frequency at which the regulator feedback loop can operate, thereby reducing a time for the phase circuit to recover from transients. 
     Comparator circuit  706  is configured to generate set signal  718  using demand current  714  and inductor current  716 . Comparator circuit  706  may, in some embodiments, be configured to compare demand current  714  to inductor current  716 , and, in response to a determination that demand current  714  is less than inductor current  716 , activate set signal  718 . In various embodiments, comparator circuit  706  may be implemented using a differential amplifier circuit, a Schmitt trigger circuit, or any other suitable comparator circuit. 
     Turning to  FIG.  8   , a block diagram of an embodiment of primary control circuit  101  is depicted. As illustrated, primary control circuit  101  includes reference generator circuit  801  and clock generator circuit  802 . 
     Reference generator circuit  801  is coupled to power supply node  305  and is configured to generate reference voltage  309 . In various embodiments, reference generator circuit  801  may be implemented as a bandgap reference circuit, or any other suitable supply and temperature independent reference circuit. In some cases, reference generator circuit  801  may include a startup circuit configured to drive reference generator circuit  801  into a known state during a power-up operation. 
     Clock generator circuit  802  is configured to generate phase clock signals  111  using clock signal  803 . In various embodiments, clock generator circuit  802  may be configured to generate phase clock signals  111  such that individual ones of phase clock signals  111  are out of phase with each other. In some cases, respective frequencies of phase clock signals  111  may be the same as a frequency of clock signal  803 , while, in other cases, the respective frequencies of phase clock signals  111  may be greater than or less than the frequency of clock signal  803 . 
     Clock generator circuit  802  may be implemented using any suitable combination of combinatorial and sequential logic circuits. In some cases, clock generator circuit  802  may include phase-locked loop or delay-locked loop circuits. Although clock generator circuit  802  is depicted as generating a single set of phase clock signals, in other embodiments, clock generator circuit  802  may generator multiple groups of phase clock signals for controlling different sets of phase circuits coupled to respective regulated power supply nodes. 
     As described above, some power converter circuits employ external driver circuits to allow for better thermal management while supplying higher load currents. In other cases, a combination of internal and external phase circuits may be employed with similar benefits. By employing both internal and external phases, a power converter may have an improved load transient response. Internal phase circuits can operate with a higher switching frequency, thereby allowing them to respond faster to a change in load before an external phase circuit can respond. Using both internal and external phase circuits can reduce undershoot and overshoot on the regulated power supply node. A block diagram of an embodiment of a power management system that employs both internal and external phase circuits is depicted. As illustrated, power management system  900  includes external phase circuit  903 , inductors  904  and  905 , and power management unit  911 , which includes control circuit  901  and internal phase circuit  902 . 
     Control circuit  901  is configured to generate external demand current  910 , internal demand current  908  and enable signal  909  using a voltage level of regulated power supply node  108 . In some embodiments, control circuit  901  may be further configured to generate a plurality of enable signals including enable signal  909 . 
     Internal phase circuit  902  is coupled to regulated power supply node  108  via inductor  904 , and is configured to source, based on the internal demand current  908 , current  906  to regulated power supply node  108  via inductor  904  during a first on-time period. In some embodiments, internal phase circuit  902  may be further to source current  906  in response to a determination that a corresponding one of the plurality of enable signals is active. 
     External phase circuit  903  coupled to regulated power supply node  108  via inductor  905 , and is configured to source, based on external demand current  910  and enable signal  909 , current  907  to regulated power supply node  108  via inductor  905  during a second on-time period. In some embodiments, external phase circuit  903  is further configured to source current  907  in response to a determination that enable signal  909  is active. 
     Although only a single internal phase circuit and a single external phase circuit are depicted in the embodiment of  FIG.  9   , in other embodiments, any suitable number of internal and external phase circuits may be employed. In some embodiments, respective numbers of internal phase circuits and external phase circuit included in power management system  900  may be based on a desired maximum load current that can be drawn from regulated power supply node  108 . 
     Turning to  FIG.  10   , a block diagram of an embodiment of a phase circuit is depicted. As illustrated, phase circuit  1000  includes driver circuit  1001 , device  1008 , device  1009 , latch circuit  1002 , comparator circuit  1006 , slope compensation circuit  1005 , and current sensor circuit  1003 . 
     Device  1008  is coupled between input power supply node  1010  and switch node  1007 , and is controlled by control signal  1020 . In a similar fashion, device  1009  is coupled between switch node  1007  and ground supply node  1011 , and is controlled by control signal  1021 . In various embodiments, switch node  1007  may be further coupled to an inductor, which is, in turn, coupled to a regulated power supply node. 
     In response to an activation of control signal  1020 , device  1008  is configured to couple input power supply node  1010  to switch node  1007 , allowing current to flow through into an inductor, magnetizing the inductor. In response to an activation of control signal  1021 , device  1009  is configured to couple switch node  1007  to ground supply node  1011 . With switch node  1007  coupled to ground supply node  1011 , energy is no longer being supplied to the inductor, causing the magnetic field of the inductor to collapse. As the magnetic field collapses, the inductor functions as a current source, providing current to the regulated power supply node. 
     In various embodiments, device  1008  may be implemented as a p-channel MOSFET, a FinFET, a GAAFET, or any other suitable transconductance device. Device  1009  may, in some embodiments, be implemented as an n-channel MOSFET, FinFET, GAAFET, or other suitable transconductance device. 
     Driver circuit  1001  is configured to generate control signal  1020  and control signal  1021  using control signal  1017 . In various embodiments, driver circuit  1001  may be configured, in response to an activation of control signal  1017 , to activate control signal  1020  and deactivate control signal  1021 . Driver circuit  1001  may be further configured, in response to a deactivation of control signal  1017 , to deactivate control signal  1020  and activate control signal  1021 . In some embodiments, driver circuit  1001  may include any suitable combination of logic gates, sequential logic circuit elements, MOSFETs, FinFETs, GAAFETs, or any other suitable transconductance devices. 
     Latch circuit  1002  is configured to deactivate control signal  1017  using reset signal  1012 , set signal  1018 , and enable signals  1022 . In some embodiments, latch circuit  1002  is configured to activate control signal  1017  in response to an activation of set signal  1018  while enable signal  1022  is active, and deactivate control signal  1017  in response to an activation of reset signal  1012  while enable signal  1022  is active. Latch circuit  1002  is configured to deactivate control signal  1017  is response to a determination that enable signal  1022  is inactive. In various embodiments, latch circuit  1002  may be implemented as a set-reset (SR) latch circuit that includes any suitable combination of logic gates. 
     Current sensor circuit  1003  is configured to generate inductor current  1016 . In various embodiments, current sensor circuit  1003  may measure a voltage drop across device  1009  and generate inductor current  1016  using the measured voltage drop. Current sensor circuit  1003  may include any suitable combination of reference and amplifier circuits. 
     Slope compensation circuit  1005  is configured to modify inductor current  1016 . In various embodiments, slope compensation circuit  1005  may be configured, in a process referred to as “slope compensation,” to combine a periodic current ramp with inductor current  1016 . It is noted that slope compensation is used to improve the stability of phase circuit  1000  by increasing a frequency at which the regulator feedback loop can operate, thereby reducing a time for phase circuit  1000  to recover from transients. 
     Comparator circuit  1006  is configured to generate set signal  1018  using demand current  1014  and inductor current  1016 . Comparator circuit  1006  may, in some embodiments, be configured to compare demand current  1014  to inductor current  1016 , and, in response to a determination that demand current  1014  is less than inductor current  1016 , activate set signal  1018 . In various embodiments, comparator circuit  1006  may be implemented using a differential amplifier circuit, a Schmitt trigger circuit, or any other suitable comparator circuit. 
     Turning to  FIG.  11   , a block diagram of an embodiment of control circuit  901  is depicted. As illustrated, control circuit  901  includes error amplifier  1101 , management circuit  1102 , current comparison circuit  1103 , and logic circuit  1111 . 
     Error amplifier  1101  is configured to generate demand current  1106  using reference voltage  1104  and feedback signal  1105 . In various embodiments, a value of feedback signal  1105  may be based on a voltage level of regulated power supply node  108 . Error amplifier  1101  may, in various embodiments, be configured generate demand current  1106  such that a value of demand current  1106  is proportional to a difference between reference voltage  1104  and feedback signal  1105 . In some embodiments, error amplifier  1101  may be implemented using a differential amplifier circuit, or any other suitable comparator circuit. 
     Management circuit  1102  is configured to generate external demand current  910  and internal demand current  908  using demand current  1106 . Although a single external demand current and a single internal demand current are depicted in the embodiment of  FIG.  11   , in other embodiments, management circuit  1102  may be configured to generate any suitable number of internal and external demand currents. In some embodiments, management circuit  1102  may be configured to scale demand current  1106  in order to generate external demand current  910  and internal demand current  908 . Management circuit  1102  may, in various embodiments, include any suitable combination of current mirror circuits, amplifier circuits, and bias circuits. 
     Current comparison circuit  1103  is configured to generate comparison signals  1109  using sensed currents  1108  and current thresholds  1107 . It is noted that sensed currents  1108  may correspond to inductor currents for inductors coupled to internal phase circuits such as internal phase circuit  902 . In various embodiments, current comparison circuit  1103  may be configured to compare a given one of sense currents  1108  to a corresponding one of current thresholds  1107  to generate a particular one of comparison signals  1109 . 
     Current comparison circuit  1103  may, in various embodiments, be implemented using multiple differential amplifier circuits, or other comparator circuits, with resistors coupled to their respective inputs in order to convert current thresholds  1107  and sensed currents  1108  to voltages for comparison. In some embodiments, additional circuits, e.g., Schmitt trigger circuits, may be used to convert the output of the differential amplifier circuits to digital values for comparison signals  1109 . 
     Logic circuit  1111  is configured to generate enable signals  1110  using comparison signals  1109 . In various embodiments, logic circuit  1111  may be configured to activate a given one of enable signals in response to a determination that a number of comparison signals  1109  has exceed a threshold value. For example, if two enable signals are active, and the comparison signals for the two phase circuits coupled to the active enable signals are active, then the current limit for the two phase circuits has been reaches, and logic circuit  1111  may activate a third enable signal to activate a third phase circuit. By generating enable signals  1110  in such a fashion, increases or decreases, in the load current drawn from regulated power supply node  108  result in a corresponding increase or decrease in the number of active phase circuits. Adjusting the number of active phase circuits can ensure that there are an adequate number of phase circuits active to supply the needed current and prevent undesirable drops in the voltage level of regulated power supply node  108 . 
     Logic circuit  1111  may, in various embodiments, be implemented using any suitable combination of combinatorial logic and sequential logic circuits. In some cases, logic circuit  1111  may be implemented as a microcontroller or general-purpose processor circuit configured to execute software or program instructions. 
     In some computer systems, different groups of functional circuits may require different power supply voltage levels. To accommodate such functional circuit blocks, a power management system may be configured to generate voltage levels on multiple regulated power supply nodes. A block diagram of an embodiment of a power management system that is configured to generate voltage levels of multiple regulated power supply nodes is depicted in  FIG.  12   . As illustrated, power management system  1200  includes controller circuits  1201  and  1202 , and external phase circuits  1204 - 1206 . 
     Controller circuit  1201  is configured to manage the voltage level of regulated power supply node  1213 , by generating control signals  1216 - 1218 . Control signals  1216  are used to control a particular phase within external phase circuits  1204 , while control signals  1217  are used to control external phase circuit  1205 . Control signals  1218  are used to control a given phase circuit within external phase circuits  1206 . As described below, external phase circuit  1206  is shared between controller circuit  1201  and controller circuit  1202 . 
     Controller circuit  1202  includes internal phase circuit  1203  and is configured to manage the voltage level of regulated power supply node  1214 . Controller circuit  1202  is configured to control the operation of internal phase circuit  1203 , which is configured to source current to regulated power supply node via inductor  1212 . Additionally, controller circuit  1202  is further configured to generate control signals  1219 , which are used to control a particular phase of external phase circuits  1206 . In various embodiments, control signals  1219  may include a demand current that is used by the particular phase of external phase circuits  1206  to determine an on-time for supply current through inductor  1211  to regulated power supply node  1214 . 
     External phase circuit  1204  include multiple phase circuit (e.g., phase circuit  1000  as depicted in  FIG.  10   ), and is coupled to power supply node  1220  and inductors  1207  and  1208 , both of which are further coupled to regulated power supply node  1213 . In various embodiments, external phase circuit  1204  is configured to source respective currents through inductors  1207  and  1208 . External phase circuit  1204  may, in some embodiments, be configured to determine an on-time for the currents through inductors  1207  and  1208  using control signals  1216 . In other embodiments, external phase circuit  1204  may be configured to determine when to start the on-time for the currents based on a demand current included in control signals  1216 . 
     External phase circuit  1205  includes a single phase circuit (e.g., phase circuit  1000  as depicted in  FIG.  10   ), and is coupled to power supply node  1221 . In various embodiments, a voltage level of power supply node  1221  may be greater than a voltage level of power supply node  1220 . External phase circuit  1205  is further coupled to inductor  1209 , which is, in turn, coupled to regulated power supply node  1213 . In some embodiments, external phase circuit  1205  is configured to source a current to regulated power supply node  1213  via inductor  1209 . By using a power supply node with a high voltage level allows external phase circuit  1205  to, in some embodiments, source additional current to regulated power supply node  1213  during periods of high load. 
     External phase circuit  1206  includes multiple phases, and is coupled to power supply node  1220  and inductors  1210  and  1211 . Inductor  1210  is further coupled to regulated power supply node  1213 , while inductor  1211  is coupled to regulated power supply node  1214 . By using different ones of the multiple phases for different power supply node  1214 . External phase circuit  1206  is shared between controller circuit  1201  and controller circuit  1202 , each controlling one phase within external phase circuit  1206  to source current to regulated power supply nodes  1213  and  1214 . Such sharing allows for providing current supply capacity to different regulated power supply nodes, while minimizing the impact on area. 
     It is noted that in some embodiments, controller circuits  1201  and  1202  may be included on a first integrated circuit, and external phase circuits  1204 - 1206  may be located on a second integrated circuit. Inductors  1207 - 1212  may be located on either the first integrated circuit, the second integrated circuit, a third integrated circuit, or elsewhere within a computer system that includes the first and second integrated circuits. Although only three controller circuits and three external phase circuits are depicted in the embodiment of  FIG.  12   , in other embodiments, any suitable number of controller circuits, external phase circuits, and power supply nodes for the external phase circuits may be employed. 
     Turning to  FIG.  13   , a flow diagram depicting an embodiment of a method for operating a power converter system is illustrated. The method, which may be applied to power converter system  100 , begins in block  1301 . 
     The method includes activating, by a first phase circuit of a plurality of phase circuits, a first driver circuit using a first phase enable signal, wherein the plurality of phase circuits and the first driver circuit are included on a first integrated circuit (block  1302 ). The method further includes activating, by a second phase circuit of the plurality of phase circuits, a second driver circuit using a second phase enable signal, wherein the second driver circuit is included on a second integrated circuit (block  1303 ). 
     In some embodiments, the second phase circuit may be further coupled to a third driver circuit that is included on the first integrated circuit. In such cases, the method may further include deactivating, by the second phase circuit, the third driver circuit based on a driver enable signal. 
     The method may, in various embodiments, also include generating, by a primary control circuit, the first and second phase enable signals, where the primary control circuit is included on the first integrated circuit. In other embodiments, the method may include generating, by the primary control circuit, the driver enable signal based on a load current being drawn from the regulated power supply node, and generating, by the primary control circuit, a reference voltage level using a voltage level of the first power supply node. 
     In various embodiments, the first driver circuit is coupled to a first power supply node and the second driver circuit is coupled to a second power supply node. In some embodiments, the plurality of phase circuits is coupled to the first power supply node. A voltage level of the second power supply node may, in various embodiments, be greater than a voltage level of the first power supply node. 
     The method also includes, in response to being activated, sourcing, by the first driver circuit, a first current to the regulated power supply node during a first on-time period (block  1304 ). In various embodiments, sourcing the first current to the regulated power supply node may include comparing the reference voltage to a voltage level of the regulated power supply node. 
     The method further includes, in response to being activated, sourcing, by the second driver circuit, a second current to the regulated power supply node during a second on-time period (block  1305 ). In various embodiments, a duration of the second on-time period may be based on a value of the second current or on a clock signal. The method concludes in block  1306 . 
     Turning to  FIG.  14   , a flow diagram depicting an embodiment of a method of operating a power management system with external phase circuit is illustrated. The method, which may be applied to power management system  900 , begin in block  1401 . 
     The method includes generating, by a control circuit in a power management unit, an external demand current and an internal demand current (block  1402 ). In various embodiments, generating, by the control circuit, the external demand current and the internal demand current includes comparing a feedback signal to a threshold value, where a value of the feedback signal is based on a voltage level of the regulated power supply node. 
     The method also includes sourcing, during a first on-time period, by a first phase circuit using the internal demand current, a first current to a regulated power supply node via a first inductor, where the first phase circuit is included in the power management unit (block  1403 ). In some embodiments, sourcing the first current includes determining a current flowing in the first inductor, and comparing the internal demand current to the current flowing in the first inductor. 
     The method further includes sourcing, during a second on-time period, by a second phase circuit using the external demand current, a second current to the regulated power supply node via a second inductor, where the second phase circuit is external to the power management unit (block  1404 ). In some embodiments, sourcing the second current includes determining a current flowing in the second inductor, and comparing the external demand current to the current flowing in the second inductor. 
     It is noted that, in some cases, the power management unit may be located on a first integrated circuit, and the second phase circuit may be located on a second integrated circuit. In some embodiments, the first and second inductors may be located on a third integrated circuit, or attached to a interposer or other substrate to which the first and second integrated circuits are also attached. 
     In various embodiments, the method may also include generating, by the control circuit, a plurality of enable signals. The method may further include sourcing, by the first phase circuit, the first current in response to determining a first enable signal of the plurality of enable signals is active, and sourcing, by the second phase circuit, the second current in response to determining a second enable signal of the plurality of enable signals is active. In some embodiments, a number of active enable signals is based on a value of a load current being drawn from the regulated power supply node. The method concludes in block  1405 . 
     A block diagram of a system-on-a-chip (SoC) is illustrated in  FIG.  15   . In the illustrated embodiment, SoC  1500  includes power management unit  1501 , processor circuit  1502 , memory circuit  1503 , and input/output circuits  1504 , each of which is coupled to power supply node  1505 . In various embodiments, SoC  1500  may be configured for use in a desktop computer, server, or in a mobile computing application such as, e.g., a tablet, laptop computer, or wearable computing device. 
     Power management unit  1501  is configured to generate a regulated voltage level on power supply node  1505  in order to provide power to processor circuit  1502 , memory circuit  1503 , and input/output circuits  1504 . In various embodiments, power management unit  1501  may employ external driver circuit  600  as depicted in  FIG.  6   , and external phase circuit  903  as depicted in  FIG.  9   . Although power management unit  1501  is depicted as generating a voltage level for a single power supply node, in other embodiments, power management unit  1501  may be configured to generate multiple voltage levels on respective power supply nodes. 
     Processor circuit  1502  may, in various embodiments, be representative of a general-purpose processor that performs computational operations. For example, processor circuit  1502  may be a central processing unit (CPU) such as a microprocessor, a microcontroller, an application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA). 
     Memory circuit  1503  may, in various embodiments, include any suitable type of memory such as a Dynamic Random-Access Memory (DRAM), a Static Random-Access Memory (SRAM), a Read-Only Memory (ROM), an Electrically Erasable Programmable Read-only Memory (EEPROM), or a non-volatile memory, for example. It is noted that although a single memory circuit is illustrated in  FIG.  15   , in other embodiments, any suitable number of memory circuits may be employed. 
     Input/output circuits  1504  may be configured to coordinate data transfer between SoC  1500  and one or more peripheral devices. Such peripheral devices may include, without limitation, storage devices (e.g., magnetic or optical media-based storage devices including hard drives, tape drives, CD drives, DVD drives, etc.), audio processing subsystems, or any other suitable type of peripheral devices. In some embodiments, input/output circuits  1504  may be configured to implement a version of Universal Serial Bus (USB) protocol or IEEE 1394 (Firewire®) protocol. 
     Input/output circuits  1504  may also be configured to coordinate data transfer between SoC  1500  and one or more devices (e.g., other computing systems or integrated circuits) coupled to SoC  1500  via a network. In one embodiment, input/output circuits  1504  may be configured to perform the data processing necessary to implement an Ethernet (IEEE 802.3) networking standard such as Gigabit Ethernet or 10-Gigabit Ethernet, for example, although it is contemplated that any suitable networking standard may be implemented. In some embodiments, input/output circuits  1504  may be configured to implement multiple discrete network interface ports. 
     Turning now to  FIG.  16   , various types of systems that may include any of the circuits, devices, or systems discussed above are illustrated. System or device  1600 , which may incorporate or otherwise utilize one or more of the techniques described herein, may be utilized in a wide range of areas. For example, system or device  1600  may be utilized as part of the hardware of systems such as a desktop computer  1610 , laptop computer  1620 , tablet computer  1630 , cellular or mobile phone  1640 , or television  1650  (or set-top box coupled to a television). 
     Similarly, disclosed elements may be utilized in a wearable device  1660 , such as a smartwatch or a health-monitoring device. Smartwatches, in many embodiments, may implement a variety of different functions—for example, access to email, cellular service, calendar, health monitoring, etc. A wearable device may also be designed solely to perform health-monitoring functions, such as monitoring a user’s vital signs, performing epidemiological functions such as contact tracing, providing communication to an emergency medical service, etc. Other types of devices are also contemplated, including devices worn on the neck, devices implantable in the human body, glasses or a helmet designed to provide computer-generated reality experiences such as those based on augmented and/or virtual reality, etc. 
     System or device  1600  may also be used in various other contexts. For example, system or device  1600  may be utilized in the context of a server computer system, such as a dedicated server or on shared hardware that implements a cloud-based service  1670 . Still further, system or device  1600  may be implemented in a wide range of specialized everyday devices, including devices  1680  commonly found in the home such as refrigerators, thermostats, security cameras, etc. The interconnection of such devices is often referred to as the “Internet of Things” (IoT). Elements may also be implemented in various modes of transportation. For example, system or device  1600  could be employed in the control systems, guidance systems, entertainment systems, etc. of various types of vehicles  1690 . 
     The applications illustrated in  FIG.  16    are merely exemplary and are not intended to limit the potential future applications of disclosed systems or devices. Other example applications include, without limitation: portable gaming devices, music players, data storage devices, unmanned aerial vehicles, etc. 
       FIG.  17    is a block diagram illustrating an example of a non-transitory computer-readable storage medium that stores circuit design information, according to some embodiments. In the illustrated embodiment, semiconductor fabrication system  1720  is configured to process the design information  1715  stored on non-transitory computer-readable storage medium  1710  and fabricate integrated circuit  1730  based on the design information  1715 . 
     Non-transitory computer-readable storage medium  1710 , may comprise any of various appropriate types of memory devices or storage devices. Non-transitory computer-readable storage medium  1710  may be an installation medium, e.g., a CD-ROM, floppy disks, or tape device; a computer system memory or random-access memory such as DRAM, DDR RAM, SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash, magnetic media, e.g., a hard drive, or optical storage; registers, or other similar types of memory elements, etc. Non-transitory computer-readable storage medium  1710  may include other types of non-transitory memory as well or combinations thereof. Non-transitory computer-readable storage medium  1710  may include two or more memory mediums, which may reside in different locations, e.g., in different computer systems that are connected over a network. 
     Design information  1715  may be specified using any of various appropriate computer languages, including hardware description languages such as, without limitation: VHDL, Verilog, SystemC, SystemVerilog, RHDL, M, MyHDL, etc. Design information  1715  may be usable by semiconductor fabrication system  1720  to fabricate at least a portion of integrated circuit  1730 . The format of design information  1715  may be recognized by at least one semiconductor fabrication system, such as semiconductor fabrication system  1720 , for example. In some embodiments, design information  1715  may include a netlist that specifies elements of a cell library, as well as their connectivity. One or more cell libraries used during logic synthesis of circuits included in integrated circuit  1730  may also be included in design information  1715 . Such cell libraries may include information indicative of device or transistor level netlists, mask design data, characterization data, and the like, of cells included in the cell library. 
     Integrated circuit  1730  may, in various embodiments, include one or more custom macrocells, such as memories, analog or mixed-signal circuits, and the like. In such cases, design information  1715  may include information related to included macrocells. Such information may include, without limitation, schematics capture database, mask design data, behavioral models, and device or transistor level netlists. As used herein, mask design data may be formatted according to graphic data system (GDSII), or any other suitable format. 
     Semiconductor fabrication system  1720  may include any of various appropriate elements configured to fabricate integrated circuits. This may include, for example, elements for depositing semiconductor materials (e.g., on a wafer, which may include masking), removing materials, altering the shape of deposited materials, modifying materials (e.g., by doping materials or modifying dielectric constants using ultraviolet processing), etc. Semiconductor fabrication system  1720  may also be configured to perform various testing of fabricated circuits for correct operation. 
     In various embodiments, integrated circuit  1730  is configured to operate according to a circuit design specified by design information  1715 , which may include performing any of the functionality described herein. For example, integrated circuit  1730  may include any of various elements shown or described herein. Further, integrated circuit  1730  may be configured to perform various functions described herein in conjunction with other components. Further, the functionality described herein may be performed by multiple connected integrated circuits. 
     As used herein, a phrase of the form “design information that specifies a design of a circuit configured to ...” does not imply that the circuit in question must be fabricated in order for the element to be met. Rather, this phrase indicates that the design information describes a circuit that, upon being fabricated, will be configured to perform the indicated actions or will include the specified components. 
     The present disclosure includes references to “embodiments,” which are nonlimiting implementations of the disclosed concepts. References to “an embodiment,” “one embodiment,” “a particular embodiment,” “some embodiments,” “various embodiments,” and the like do not necessarily refer to the same embodiment. A large number of possible embodiments are contemplated, including specific embodiments described in detail, as well as modifications or alternatives that fall within the spirit or scope of the disclosure. Not all embodiments will necessarily manifest any or all of the potential advantages described herein. 
     Unless stated otherwise, the specific embodiments are not intended to limit the scope of claims that are drafted based on this disclosure to the disclosed forms, even where only a single example is described with respect to a particular feature. The disclosed embodiments are thus intended to be illustrative rather than restrictive, absent any statements to the contrary. The application is intended to cover such alternatives, modifications, and equivalents that would be apparent to a person skilled in the art having the benefit of this disclosure. 
     Particular features, structures, or characteristics may be combined in any suitable manner consistent with this disclosure. The disclosure is thus intended to include any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims. 
     For example, while the appended dependent claims are drafted such that each depends on a single other claim, additional dependencies are also contemplated. Where appropriate, it is also contemplated that claims drafted in one statutory type (e.g., apparatus) suggest corresponding claims of another statutory type (e.g., method). 
     Because this disclosure is a legal document, various terms and phrases may be subject to administrative and judicial interpretation. Public notice is hereby given that the following paragraphs, as well as definitions provided throughout the disclosure, are to be used in determining how to interpret claims that are drafted based on this disclosure. 
     References to the singular forms such “a,” “an,” and “the” are intended to mean “one or more” unless the context clearly dictates otherwise. Reference to “an item” in a claim thus does not preclude additional instances of the item. 
     The word “may” is used herein in a permissive sense (i.e., having the potential to, being able to) and not in a mandatory sense (i.e., must). 
     The terms “comprising” and “including,” and forms thereof, are open-ended and mean “including, but not limited to.” 
     When the term “or” is used in this disclosure with respect to a list of options, it will generally be understood to be used in the inclusive sense unless the context provides otherwise. Thus, a recitation of “x or y” is equivalent to “x or y, or both,” covering x but not y, y but not x, and both x and y. On the other hand, a phrase such as “either x or y, but not both” makes clear that “or” is being used in the exclusive sense. 
     A recitation of “w, x, y, or z, or any combination thereof” or “at least one of ... w, x, y, and z” is intended to cover all possibilities involving a single element up to the total number of elements in the set. For example, given the set [w, x, y, z], these phrasings cover any single element of the set (e.g., w but not x, y, or z), any two elements (e.g., w and x, but not y or z), any three elements (e.g., w, x, and y, but not z), and all four elements. The phrase “at least one of ... w, x, y, and z” thus refers to at least one of element of the set [w, x, y, z], thereby covering all possible combinations in this list of options. This phrase is not to be interpreted to require that there is at least one instance of w, at least one instance of x, at least one instance of y, and at least one instance of z. 
     Various “labels” may proceed nouns in this disclosure. Unless context provides otherwise, different labels used for a feature (e.g., “first circuit,” “second circuit,” “particular circuit,” “given circuit,” etc.) refer to different instances of the feature. The labels “first,” “second,” and “third” when applied to a particular feature do not imply any type of ordering (e.g., spatial, temporal, logical, etc.), unless stated otherwise. 
     Within this disclosure, different entities (which may variously be referred to as “units,” “circuits,” other components, etc.) may be described or claimed as “configured” to perform one or more tasks or operations. This formulation—[entity] configured to [perform one or more tasks]—is used herein to refer to structure (i.e., something physical). More specifically, this formulation is used to indicate that this structure is arranged to perform the one or more tasks during operation. A structure can be said to be “configured to” perform some task even if the structure is not currently being operated. Thus, an entity described or recited as “configured to” perform some task refers to something physical, such as a device, circuit, memory storing program instructions executable to implement the task, etc. This phrase is not used herein to refer to something intangible. 
     The term “configured to” is not intended to mean “configurable to.” An unprogrammed FPGA, for example, would not be considered to be “configured to” perform some specific function. This unprogrammed FPGA may be “configurable to” perform that function, however. 
     Reciting in the appended claims that a structure is “configured to” perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112(f) for that claim element. Should Applicant wish to invoke Section 112(f) during prosecution, it will recite claim elements using the “means for” [performing a function] construct. 
     The phrase “based on” is used to describe one or more factors that affect a determination. This term does not foreclose the possibility that additional factors may affect the determination. That is, a determination may be solely based on specified factors or based on the specified factors as well as other, unspecified factors. Consider the phrase “determine A based on B.” This phrase specifies that B is a factor that is used to determine A or that affects the determination of A. This phrase does not foreclose that the determination of A may also be based on some other factor, such as C. This phrase is also intended to cover an embodiment in which A is determined based solely on B. As used herein, the phrase “based on” is synonymous with the phrase “based at least in part on.” 
     The phrase “in response to” describes one or more factors that trigger an effect. This phrase does not foreclose the possibility that additional factors may affect or otherwise trigger the effect. That is, an effect may be solely in response to those factors, or may be in response to the specified factors as well as other, unspecified factors. Consider the phrase “perform A in response to B.” This phrase specifies that B is a factor that triggers the performance of A. This phrase does not foreclose that performing A may also be in response to some other factor, such as C. This phrase is also intended to cover an embodiment in which A is performed solely in response to B.