System and method for providing variable gain loop control for use in adaptive voltage scaling
AssigneeNational Semiconductor Corporation
InventorPasi Salmi
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Abstract
A system and method is disclosed for providing efficient closed loop feedback control in an adaptive voltage scaling system. The closed loop feedback circuitry of the invention comprises variable feedback gain for an error amplifier circuit. In one embodiment the variable feedback gain comprises a low value of feedback gain and a high value of feedback gain. The value of feedback gain that is employed determines the speed of response of the system (1) to performance level changes of an adjustable supply voltage, and (2) to disturbances such as temperature changes, IR voltage drops, and ripple voltages. The variable feedback gain feature enables the use of adaptive voltage scaling regulators that have outputs with relatively high ripple voltage.
Claims20
An apparatus for providing closed loop feedback control in an adaptive voltage scaling system, said apparatus comprising closed loop feedback circuitry having a variable feedback gain;
- and
- an error amplifier circuit that is capable of alternately operating with one of:
- a low value of feedback gain and a high value of feedback gain;
- circuitry for selecting one of said low value of feedback gain and said high value of feedback gain a hardware performance monitor that is capable of generating a slack time error signal;
- and
- a voltage monitor that is capable of receiving said slack time error signal from said hardware performance monitor and, based on a value of said slack time error signal evaluating suitability of a supply voltage of said adaptive voltage scaling system for a requested performance level of said adaptive voltage scaling system.
A method for changing a level of an adjustable supply voltage in an adaptive voltage scaling system, said method comprising the steps of:
- receiving from a central processing unit a request for a new operating clock frequency;
- determining that said requested new operating clock frequency is a higher frequency than a current operating clock frequency;
- selecting a high value of feedback gain for an error amplifier that is capable of alternately operating with one of:
- a low value of feedback gain and a high value of feedback gain;
- operating said error amplifier with said high value of feedback gain;
- and
- sending at least one voltage change command to an adaptive voltage scaling regulator of said adaptive voltage scaling system.
A method for changing a level of an adjustable supply voltage in an adaptive voltage scaling system, said method comprising the steps of:
- receiving from a central processing unit a request for a new operating clock frequency;
- determining that said requested new operating clock frequency is a lower frequency than a current operating clock frequency;
- enabling said new operating clock frequency to said central processing unit;
- selecting a high value of feedback gain for an error amplifier that is capable of alternately operating with one of:
- a low value of feedback gain and a high value of feedback gain;
- operating said error amplifier with said high value of feedback gain;
- and
- sending at least one voltage change command to an adaptive voltage scaling regulator of said adaptive voltage scaling system.
A method for maintaining a level of an adjustable supply voltage in an adaptive voltage scaling system, said method comprising the steps of:
- determining that a central processing unit of said adaptive voltage scaling system is not requesting a new operating clock frequency;
- determining that gate delay of said adaptive voltage scaling system is one of:
- increasing due to a disturbance and decreasing due to a disturbance;
- and
- in response to a determination of increasing gate delay, increasing a level of said adjustable supply voltage;
- and
- in response to a determination of decreasing gate delay, decreasing a level of said adjustable supply voltage.
Dependencies are inferred from the claim text.