Managing on-chip power rail between internal power supply and external power supply

Abstract

A system may include an integrated circuit comprising an on-chip power supply and an internal power rail, a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed, and a control circuit configured to monitor conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states and based on the conditions, control a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch.

Claims

1. A system comprising: an integrated circuit comprising an on-chip power supply and an internal power rail; a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed; and a control circuit configured to: monitor conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, control a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a voltage generated by the on-chip power supply is above a load-dependent threshold voltage.

2. The system of claim 1, wherein the control circuit is configured to, prior to the gate-controlled supply switch transitioning between switch states, precondition internal nodes of the on-chip power supply.

3. The system of claim 1, wherein the control circuit is configured to regulate a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

4. A system comprising: an integrated circuit comprising an on-chip power supply and an internal power rail; a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed; and a control circuit configured to: monitor conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, control a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a switch current through the gate-controlled supply switch is below a threshold current.

5. The system of claim 4, wherein the control circuit is configured to, prior to the gate-controlled supply switch transitioning between switch states, precondition internal nodes of the on-chip power supply.

6. The system of claim 4, wherein the control circuit is configured to regulate a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

7. A system comprising: an integrated circuit comprising an on-chip power supply and an internal power rail; a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed; and a control circuit configured to: monitor conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, control a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a current generated by the on-chip power supply is above a threshold current.

8. The system of claim 7, wherein the control circuit is configured to, prior to the gate-controlled supply switch transitioning between switch states, precondition internal nodes of the on-chip power supply.

9. The system of claim 7, wherein the control circuit is configured to regulate a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

10. A system comprising: an integrated circuit comprising an on-chip power supply and an internal power rail; a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed; and a control circuit configured to: monitor conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, control a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a gate voltage of the gate-controlled supply switch is below a threshold voltage.

11. The system of claim 10, wherein the control circuit is configured to, prior to the gate-controlled supply switch transitioning between switch states, precondition internal nodes of the on-chip power supply.

12. The system of claim 10, wherein the control circuit is configured to regulate a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

13. A method, in a system comprising an integrated circuit comprising an on-chip power supply and an internal power rail and a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed, the method comprising: monitoring conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, controlling a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a voltage generated by the on-chip power supply is above a load-dependent threshold voltage.

14. The method of claim 13, further comprising, prior to the gate-controlled supply switch transitioning between switch states, preconditioning internal nodes of the on-chip power supply.

15. The method of claim 13, further comprising regulating a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

16. A method, in a system comprising an integrated circuit comprising an on-chip power supply and an internal power rail and a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed, the method comprising: monitoring conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, controlling a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a switch current through the gate-controlled supply switch is below a threshold current.

17. The method of claim 16, further comprising, prior to the gate-controlled supply switch transitioning between switch states, preconditioning internal nodes of the on-chip power supply.

18. The method of claim 16, further comprising regulating a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

19. A method, in a system comprising an integrated circuit comprising an on-chip power supply and an internal power rail and a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed, the method comprising: monitoring conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, controlling a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a current generated by the on-chip power supply is above a threshold current.

20. The method of claim 19, further comprising, prior to the gate-controlled supply switch transitioning between switch states, preconditioning internal nodes of the on-chip power supply.

21. The method of claim 19, further comprising regulating a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

22. A method, in a system comprising an integrated circuit comprising an on-chip power supply and an internal power rail and a gate-controlled supply switch configured to be coupled between the on-chip power supply and an external power supply such that the internal power rail is regulated by the on-chip power supply when the gate-controlled supply switch is open and the internal power rail is regulated by the external power supply when the gate-controlled supply switch is closed, the method comprising: monitoring conditions associated with the on-chip power supply when the gate-controlled supply switch is transitioning between switch states; and based on the conditions, controlling a rate of charging or discharging of a capacitance coupled to a gate of the gate-controlled supply switch, wherein controlling the rate of charging or discharging of the capacitance comprises increasing the rate of discharging of the capacitance when a gate voltage of the gate-controlled supply switch is below a threshold voltage.

23. The method of claim 22, further comprising, prior to the gate-controlled supply switch transitioning between switch states, preconditioning internal nodes of the on-chip power supply.

24. The method of claim 22, further comprising regulating a load as seen by the on-chip power supply during transitioning of the gate-controlled supply switch by controlling a gate of the gate-controlled supply switch.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

(2) FIG. 1 illustrates a block diagram of selected components of an example electronic device, as is known in the art;

(3) FIGS. 2A and 2B illustrate graphs of example waveforms of selected voltages and currents within the electronic device shown in FIG. 1, as is known in the art;

(4) FIG. 3 illustrates a block diagram of selected components of an example electronic device, in accordance with embodiments of the present disclosure;

(5) FIG. 4 illustrates graphs of example waveforms of a switch control signal and a rail voltage within the electronic device shown in FIG. 3, in accordance with embodiments of the present disclosure;

(6) FIGS. 5A and 5B (which may collectively be referred to as FIG. 5 herein) illustrate a circuit diagram of selected components of a current-steering circuit for performing need-based soft-open and soft-close for a supply switch, in accordance with embodiments of the present disclosure;

(7) FIG. 6 illustrates graphs of example waveforms of a switch control signal and a rail voltage within the electronic device shown in FIG. 3 using the current-steering circuit of FIG. 5, in accordance with embodiments of the present disclosure;

(8) FIG. 7 illustrates selected components of an example LDO that may be implemented within an on-chip supply, in accordance with embodiments of the present disclosure;

(9) FIG. 8 illustrates graphs of example waveforms of a rail voltage and an internal reference voltage within the LDO shown in FIG. 7, in accordance with embodiments of the present disclosure;

(10) FIG. 9 illustrates selected components of another example LDO that may be implemented within an on-chip supply, in accordance with embodiments of the present disclosure;

(11) FIG. 10 illustrates graphs of example waveforms of a rail voltage and an internal voltage within the LDO shown in FIG. 9, in accordance with embodiments of the present disclosure;

(12) FIG. 11 illustrates an example transfer function of a current limit for a supply switch as a function of a voltage difference, in accordance with embodiments of the present disclosure;

(13) FIG. 12 illustrates a circuit diagram of selected components of a current-limiting circuit for performing the current-limiting shown in FIG. 11, in accordance with embodiments of the present disclosure; and

(14) FIG. 13 illustrates an example state diagram for a supply sequencer, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

(15) FIG. 3 illustrates a block diagram of selected components of an example electronic device 100, in accordance with embodiments of the present disclosure. As shown in FIG. 3, electronic device 100 may include an integrated circuit 112 having an internal on-chip power supply 114 (e.g., a low-dropout regulator or LDO) for regulating an on-chip power rail VD.sub.CORE, and a high-efficiency power supply 116 external to integrated circuit 112 and coupled to the on-chip power rail via a supply switch 118 internal to integrated circuit 112. As also shown in FIG. 3, a load current I.sub.LOAD1 may be drawn by components of integrated circuit 112 as represented by current sink 120 and a load current I.sub.LOAD2 may be drawn by components of electronic device 100 external to integrated circuit 112 as represented by current sink 122.

(16) As also shown in FIG. 3, and described in further detail below, electronic device 100 may include a control circuit 130 (e.g., a microcontroller unit) configured to generate a control signal for selectively opening and closing supply switch 118. As also described in further detail below, control circuit 130 may also be configured to generate control signals for controlling operation of on-chip power supply 114.

(17) Electronic device 100 as shown in FIG. 3 may operate in two steady state modes of operation:

(18) (a) a first mode in which supply switch 118 is open (e.g., deactivated, off, disabled) in which load current I.sub.LOAD1 may be supplied from on-chip power supply 114; and

(19) (b) a second mode in which supply switch 118 is closed (e.g., activated, on, enabled) in which load current I.sub.LOAD1 may be supplied from external power supply 116 and on-chip power supply 114 may be turned off or disabled.

(20) The mode of operation may be chosen based on system power states, power consumption optimization, and/or other factors which are beyond the scope of this disclosure.

(21) In operation, and as also described in greater detail below, control circuit 130 may operate to reduce or eliminate the disadvantages contemplated in the Background section of this disclosure. For example, to reduce or eliminate overshoot of voltage on on-chip power rail VD.sub.CORE in response to opening of supply switch 118 and/or to reduce or eliminate damage or reliability issues that may result from switch current I.sub.SWITCH exceeding a safe current limit, control circuit 130 may employ a current limiter 132 to limit switch current I.sub.SWITCH. As another example, to reduce or eliminate undershoot of voltage on on-chip power rail VD.sub.CORE in response to opening of supply switch 118, control circuit 130 may include a soft-open controller 134 to perform a “soft opening” of supply switch 118. In addition or alternatively, to reduce or eliminate undershoot of voltage on on-chip power rail VD.sub.CORE in response to opening of supply switch 118, control circuit 130 may also control internal analog state variables which may be used to speed up a slow switch transition. As another example, to reduce or eliminate undershoot and/or overshoot of voltage on on-chip power rail VD.sub.CORE in response to transitions of supply switch 118, control circuit 130 may, via communication of a reference selection control signal REF_SEL and communication of supply parameters SUPPLY_PARAM to on-chip power supply 114, internally precondition on-chip power supply 114 based on knowledge of opening and closing events of supply switch 118. As also shown in FIG. 3, control circuit 130 may include a supply sequencer 136 configured to sequence switching of supply switch 118 and other components of electronic device 100.

(22) FIG. 4 illustrates graphs of example waveforms of a switch control signal V.sub.GATE for selectively enabling supply switch 118 and rail voltage VD.sub.CORE, in accordance with embodiments of the present disclosure. An example waveform for switch control signal V.sub.GATE using a traditional soft-open scheme for supply switch 118 is shown in the example waveforms of switch control signal V.sub.GATE in FIG. 4. Although a traditional soft-open scheme may reduce overshoot/undershoot and peak current issues, the time required to make such open/close transitions may be too long for specific applications such as a power management integrated circuit. However, there may exist regions during the transition of switch control signal V.sub.GATE from closed to open which may be used to minimize the time required for transition by modulating the rate of charge or discharge of switch control signal V.sub.GATE. Such regions are depicted in FIG. 4 as regions A, B, and C, and may be described as follows:

(23) Region A: a time during which on-chip power rail VD.sub.CORE does not respond to opening or closing of supply switch 118.

(24) Region B: a time during which electrical current supported by external power supply 116 being disengaged has fallen below a predetermined level.

(25) Region C: a time during which switch current I.sub.SWITCH has fallen below a predetermined level.

(26) Accordingly, soft-open controller 134 may be configured to perform a need-based soft-open scheme as shown in FIG. 4 to reduce soft-opening time used in traditional approaches. Soft-open controller 134 may perform such need-based soft-open scheme in any suitable manner. For example, in some embodiments, soft-open controller 134 may monitor on-chip power rail VD.sub.CORE and use feedback to drive switch control signal V.sub.GATE. As a specific example, when on-chip power rail VD.sub.CORE is above a predetermined threshold voltage, soft-open controller 134 may increase a discharging rate from a capacitance coupled to the electrical node of switch control signal V.sub.GATE. In addition or alternatively, soft-open controller 134 may monitor an electrical current output by either of on-chip power supply 114 or external power supply 116 and use feedback to drive switch control signal V.sub.GATE. As a specific example, when the electrical current delivered from on-chip power supply 114 is above a predetermined threshold current, soft-open controller 134 may increase a discharging rate from a capacitance coupled to the electrical node of switch control signal V.sub.GATE. In addition or alternatively, soft-open controller 134 may monitor switch current I.sub.SWITCH and use feedback to drive switch control signal V.sub.GATE. As a specific example, when switch current I.sub.SWITCH is below a predetermined threshold current, soft-open controller 134 may increase a discharging rate from a capacitance coupled to the electrical node of switch control signal V.sub.GATE. In addition or alternatively, soft-open controller 134 may utilize a timer-based approach wherein different discharge rates from a capacitance coupled to the electrical node of switch control signal V.sub.GATE are applied at various intervals based on known system behavior.

(27) FIG. 5 illustrates a circuit diagram of selected components of a current-steering circuit 500 which may be implemented by soft-open controller 134 for performing need-based soft-open and soft-close for supply switch 118, in accordance with embodiments of the present disclosure. FIG. 6 illustrates graphs of example waveforms of switch control signal V.sub.GATE and rail voltage VD.sub.CORE using current-steering circuit 500 of FIG. 5, in accordance with embodiments of the present disclosure. Current-steering circuit 500 may be configured to regulate a discharge rate of a capacitance coupled to the voltage node of switch control signal V.sub.GATE in order to implement a need-based soft open scheme. As shown in FIG. 5, current-steering circuit 500 may receive a switch enable signal SWITCH_EN as an input. Current-steering circuit 500 may include a soft-close subcircuit 502 and a soft-open subcircuit 504, both configured to regulate switch control signal V.sub.GATE based on conditions within electronic circuit 100. As shown in FIG. 5, soft-open portion 504 may include a voltage comparison portion 506 that generates a current I.sub.FAST1, a current comparison portion 508 that generates a current I.sub.FAST2, a constant pulldown portion 510 that generates a current I.sub.SLOW, and a final fast pulldown portion 512 that generates a current I.sub.SCHMITT. Circuit details of each subcircuit and portion are shown in FIG. 5 and not described in detail, as those of skill in the art should appreciate how the detailed circuitry accomplishes the functionality of each subcircuit and portion.

(28) As shown in FIG. 6, current-steering circuit 500 may apply current I.sub.FAST1 to discharge switch control signal V.sub.GATE when the following conditions are true:

(29) (a) a higher external voltage VD.sub.EXT, with supply switch 118 closed, has pulled rail voltage VD.sub.CORE higher than a predetermined reference voltage V.sub.BG_REF2; and

(30) (b) rail voltage VD.sub.CORE has not started to decrease, which occurs right before a load transition, which may be indicated by internally-generated rail voltage VD.sub.CORE being greater than or equal to external voltage VD.sub.EXT generated by on-chip power supply 114.

(31) As also shown in FIG. 6, current-steering circuit 500 may apply current I.sub.FAST2 to discharge switch control signal V.sub.GATE when the following conditions are true:

(32) (a) the load handover to on-chip power supply 114 has already occurred, which may be indicated by an indicator voltage V.sub.LDO_SW being less than rail voltage VD.sub.CORE; and

(33) (d) on-chip power supply 114 is not overshooting, as indicated by VD.sub.CORE being lower than or equal to predetermined reference voltage V.sub.BG_REF2.

(34) As further shown in FIG. 6, when the conditions for applying currents I.sub.FAST1 and I.sub.FAST2 are not met, current-steering circuit 500 may apply current I.sub.SLOW to discharge switch control signal V.sub.GATE in a load transition region. In addition, current-steering circuit 500 may apply current I.sub.SCHMITT to quickly discharge switch control signal V.sub.GATE in final pulldown at the end of the switching transition once switch control signal V.sub.GATE reaches a threshold voltage V.sub.SCHMITT.

(35) As described above, supply sequencer 136 may reduce or eliminate undershoot and/or overshoot of voltage on on-chip power rail VD.sub.CORE in response to transitions of supply switch 118, and control circuit 130 may, via communication of a reference selection control signal REF_SEL and communication of supply parameters SUPPLY_PARAM to on-chip power supply 114, internally precondition on-chip power supply 114 based on knowledge of opening and closing events of supply switch 118. For example, FIG. 7 illustrates selected components of an example LDO 700 that may be implemented within on-chip power supply 114, in accordance with embodiments of the present disclosure. As shown in FIG. 7, LDO 700 may include an operational amplifier 702 configured to regulate rail voltage VD.sub.CORE in accordance with an internal reference voltage V.sub.REF. As further shown in FIG. 7, LDO 700 may include a switch 704, under the control of reference selection control signal REF_SEL, configured to select internal reference voltage V.sub.REF from either of a first reference voltage V.sub.REF1 and a second reference voltage V.sub.REF2, wherein V.sub.REF2>V.sub.REF1. In operation, supply sequencer 136 may increase reference voltage Vii from first reference voltage V.sub.REF1 to second reference voltage V.sub.REF2 during transition of supply switch 118 in order to reduce an undershoot of rail voltage VD.sub.CORE below first reference voltage V.sub.REF1, as shown in FIG. 8.

(36) As another example, FIG. 9 illustrates selected components of an example LDO 900 that may be implemented within on-chip power supply 114, in accordance with embodiments of the present disclosure. As shown in FIG. 9, LDO 900 may include an operational amplifier 902, diode clamp 904, and transistor 906 arranged as shown and configured to regulate rail voltage VD.sub.CORE in accordance with an internal reference voltage V.sub.REF. In operation, diode clamp 904 may clamp an internal voltage V.sub.INT at the cathode of diode clamp 904 and gate terminal of transistor 906 to a minimum voltage, which in turn may reduce an undershoot of rail voltage VD.sub.CORE below first reference voltage V.sub.REF1, as shown in FIG. 10.

(37) In addition to using diode clamp 904 to prime internal nodes of LDO 900 in order to meet load demands, on-chip power supply 114 may include other mechanisms for priming internal nodes of LDO 900, including clamping a slowest moving electrical node, charging a gate of an output transistor to a constant predetermined value, increasing current to an output stage of LDO 900, and/or other suitable mechanisms.

(38) In some embodiments, features of both LDO 700 of FIG. 7 and LDO 900 of FIG. 9 may be combined.

(39) As described above, to reduce or eliminate overshoot of voltage on on-chip power rail VD.sub.CORE in response to opening of supply switch 118 and/or to reduce or eliminate damage or reliability issues that may result from switch current I.sub.SWITCH exceeding a safe current limit, control circuit 130 may employ current limiter 132 to limit switch current I.sub.SWITCH. For example, current limiter 132 may apply a current limit I.sub.LIM to switch current I.sub.SWITCH which is a function of a difference ΔV between external supply voltage VD.sub.EXT and rail voltage VD.sub.CORE (e.g., ΔV=VD.sub.EXT−VD.sub.CORE) and the expected resistance of supply switch 132. FIG. 11 illustrates an example transfer function of current limit as a function of difference ΔV between external supply voltage VD.sub.EXT and rail voltage VD.sub.CORE, in accordance with embodiments of the present disclosure. In the example shown in FIG. 11, when difference ΔV is negative and greater than a threshold magnitude, current limit I.sub.LIM may have a fixed maximum negative value. Current limiter 132 may implement current limiting in any suitable manner, including an analog feedback loop that drives a gate of supply switch 118 based on a measured difference ΔV across supply switch 118, or a mixed signal approach in which a fixed gate voltage V.sub.GATE is applied to limit switch current I.sub.SWITCH while rail voltage VD.sub.CORE is charging above. FIG. 12 illustrates a circuit diagram of selected components of a current-limiting circuit for performing the current-limiting shown in FIG. 11, in accordance with embodiments of the present disclosure. The circuit shown in FIG. 12 may limit switch current I.sub.SWITCH by comparing external supply voltage VD.sub.EXT against a sensor device (e.g., the n-type field-effect transistor labeled “1x” in FIG. 12) that mimics supply switch 118 (e.g., the n-type field-effect transistor labeled “32x” in FIG. 12) and that is biased with a current representative of the current limit I.sub.LIM (e.g., 600 μA).

(40) FIG. 13 illustrates an example state diagram for supply sequencer 136, in accordance with embodiments of the present disclosure. State sequencing of various components of electronic circuit 100 may be required to manage power transitions resulting from opening and/or closing of supply switch 118. The transition to rail voltage VD.sub.CORE being taken over by on-chip power supply 114 may require state variable initializations and current/switch gate control mechanisms to keep rail voltage VD.sub.CORE from collapsing. However, assuming that external power supply 116 is not current- or bandwidth-limited like on-chip power supply 114, not as much care may be needed when handing control of rail voltage VD.sub.CORE to external power supply 116. Nonetheless, in the event external power supply 116 is current- or bandwidth-limited, state sequencing mechanisms for transitioning supply switch 118 from opened to closed may be employed similar to those shown in FIG. 13 for transitioning supply switch 118 from closed to opened.

(41) As used herein, when two or more elements are referred to as “coupled” to one another, such term indicates that such two or more elements are in electronic communication or mechanical communication, as applicable, whether connected indirectly or directly, with or without intervening elements.

(42) This disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, alterations, and modifications to the example embodiments herein that a person having ordinary skill in the art would comprehend. Moreover, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, or component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Accordingly, modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set.

(43) Although exemplary embodiments are illustrated in the figures and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described above.

(44) Unless otherwise specifically noted, articles depicted in the drawings are not necessarily drawn to scale.

(45) All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the disclosure and the concepts contributed by the inventor to furthering the art, and are construed as being without limitation to such specifically recited examples and conditions. Although embodiments of the present disclosure have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the disclosure.

(46) Although specific advantages have been enumerated above, various embodiments may include some, none, or all of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the foregoing figures and description.

(47) To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. § 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.