Patent Application
20080150614
This invention relates to supply voltages and current requirements for circuit blocks within integrated circuits.
Circuit blocks in integrated circuits often operate at a speed determined in part by the supply voltage applied to the circuit block. In addition, the operational speed of integrated circuit blocks will typically vary due to manufacturing process variations and environmental parameters, such as temperature changes. As these process and environmental conditions change for a given circuit block, both the maximum possible operational speed and current consumption of the circuit will also change. These variations can cause problems for integrated circuit due to performance degradations if speed capabilities drop too far. As such, integrated circuits are often designed such that operational integrity is maintained for the worst cases within an expected range of process variations and environmental conditions during circuit operation. However, this technique can cause an undesirable increase in power consumption where greater operational speed capabilities are provided than are needed by the circuit block during its operation.
A system and method are disclosed for dynamic supply voltage biasing of circuit blocks within an integrated circuit. By providing a dynamic supply voltage for circuit blocks, operational integrity can be maintained while reducing power consumption. As described herein, a dynamic supply voltage can be correlated to process variations and environmental parameters so that circuit blocks can be operated at a desired speed while still reducing the power required for this operation. To implement this dynamic supply voltage regulation, circuit elements are provided within a variable supply voltage circuit that cause an output supply voltage to vary dynamically based upon operational parameters such as process variations or environment parameters or both. As such, circuit blocks can be provided a supply voltage high enough to allow operational integrity at required speeds but not so high as to waste power by unnecessarily increasing current consumption, and this supply voltage can dynamically adjust itself during operation. As described below, other features and variations can be implemented, if desired, and related systems and methods can be utilized, as well.
It is noted that the appended drawings illustrate only exemplary embodiments of the invention and are, therefore, not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
A system and method are disclosed for dynamic supply voltages biasing based upon current requirements for circuit blocks within integrated circuits. By dynamically biasing the supply voltage for the circuit block based upon the current requirements for the circuit block, operational integrity can be maintained while reducing power consumption. As described below, a circuit block is provided a dynamic supply voltage high enough to allow operational integrity at required speeds but not so high as to waste power by unnecessarily increasing current consumption. To implement this dynamic supply regulation, circuit elements are provided within a variable supply voltage circuit that cause an output supply voltage to vary dynamically based upon operational parameters such as process variations or environment parameters or both. As described herein, the dynamic biasing of the supply voltage to the circuit block helps to lower overall current consumption, thereby improving the power performance of the circuit block and the integrated circuit.
To achieve a desired operating speed, a certain level of supply voltage should be applied to the circuit block. For the first speed (SP1) 206, if the circuit block resulted from a slow process variation as represented by line (SLOW) 210, a first slow supply voltage level (VS1) is applied to the circuit block to achieve the desired operating speed. If the circuit block resulted from a typical process variation as represented by line (TYPICAL) 212, a first typical supply voltage level (VT1) is applied to the circuit block to achieve the desired operating speed. And if the circuit block resulted from a fast process variation as represented by line (FAST) 214, a first fast supply voltage level (VF1) is applied to the circuit block to achieve the desired operating speed. Similarly, for the second speed (SP2) 208, if the circuit block resulted from a slow process variation as represented by line (SLOW) 210, a second slow supply voltage level (VS2) is applied to the circuit block to achieve the desired operating speed. If the circuit block resulted from a typical process variation as represented by line (TYPICAL) 212, a second typical supply voltage level (VT2) is applied to the circuit block to achieve the desired operating speed. And if the circuit block resulted from a fast process variation as represented by line (FAST) 214, a second fast supply voltage level (VF2) is applied to the circuit block to achieve the desired operating speed. As can be seen with respect to
It is also noted that the operational speed of a circuit block will also vary according to environmental parameters, such as temperature. A similar diagram to
As described below, generating a supply voltage that varies dynamically based upon process variations and environmental parameters allows an efficient control of the current consumption of the part. This dynamic supply voltage biasing provides enough supply voltage to maintain a desired operation speed while reducing the amount of power that would have been consumed if a constant supply voltage were used that would be enough to handle any process variation and environmental change within an expected range of operation.
In this example circuit embodiment, the voltage drop across the two diode-connected MOS transistors 308 and 310 will tend to vary with process variations and/or environment changes, such as temperature changes. As such, the output reference voltage (VREF) will also tend to vary dynamically with process variations and/or environment parameters during operation of the integrated circuit. This variable output reference voltage (VREF) can then be utilized to generate a dynamic supply voltage that will also dynamically vary with process variations and/or environment parameters. This dynamic supply voltage can then be used as an indication of the ideal supply voltage for a circuit block such that the circuit block can operate at a desired operational speed without consuming an unnecessary amount of current. The dynamic supply voltage will adjust itself based upon process variations and environmental changes so that an adequate supply voltage is provided to maintain desired operational speeds for the circuit block while reducing the current consumption from what would have been consumed using a constant supply voltage level set high enough to cover all expected process and environmental variations.
It is noted that the slope (α) 318 for the linear response 320 can be selected to be any desired value. For example, a value of about one can be selected. Making the slope (α) 318 about one will tend to provide a stable solution. A value for the slope (α) 318 greater than one will tend to cause the dynamically regulated supply voltage (VSUPPLY) to vary more aggressively, and the setup will typically be less reliable. A value for the slope (α) 318 smaller than one will typically cause the dynamically regulated supply voltage (VSUPPLY) to vary less aggressively, and the setup will typically be more reliable. A value for the slope (α) 318 of zero will cause the regulated supply voltage (VSUPPLY) to be constant. It is again noted, however, that the value for the slope (α) 318 can be selected as desired depending upon the operational objectives desired. It is also noted that relationships, other than a linear relationship, between the dynamic supply voltage (VSUPPLY) and the dynamic output reference voltage (VREF) can be utilized, as desired.
In this example circuit embodiment, the voltage drop across the two NMOS transistors 410 and 412 will tend to vary with process variations and/or environment changes, such as temperature changes. As such, the voltage at node 405 that is applied to the gate of PMOS transistor (MP1) 414 will also tend to vary dynamically with process variations and/or environment parameters during operation of the integrated circuit. In turn, this variable gate voltage for PMOS transistor (MP1) 414 will cause the voltage at its source, which is applied to node 408, to vary dynamically with process variations and/or environment parameters during operation of the integrated circuit. This output node 408 can then be used as a dynamically regulated supply voltage (VSUPPLY) that will also vary with process variations and/or environment parameters. This dynamic supply voltage can then be used as a supply voltage for a circuit block such as CMOS VCO 418. As such, the CMOS VCO 418 can then operate a desired operational speed without consuming an unnecessary amount of current.
It is noted that for this implementation, the output voltage at node 408 will vary as a function of the bias current (IBIAS) through the NMOS transistors 410 and 412 and the PMOS transistor 414. The NMOS transistor (MN1) 412 can be configured to operate in its triode region, and the NMOS transistor (MN2) 410 and the PMOS transistor (MP1) 414 can be configured to operate in their respective saturation regions. As such, the voltage characteristics of node 408, which is the source of PMOS transistor (MP1) 414, will vary according the bias current (IBIAS). Thus, as the bias current (IBIAS) varies with process and environmental variations, the voltage at node 408 will also vary, and this voltage can be used as a dynamically regulated supply voltage for circuit blocks. It is further noted that the reference bias current (IBIAS) can be designed such that the resulting current after flowing through the triode MOS devices can be relatively independent of process and/or temperature variations. Although in the end, the reference bias current (IBIAS) will likely depend on some voltage and some resistance, and, as such, the reference bias current (IBIAS) itself will likely have some variation due to the operational conditions for the integrated circuit.
As described herein, therefore, circuit blocks within integrated circuits can be biased with dynamic supply voltages so that their operational integrity is maintained through process and environmental changes while their current consumption is reduced. The dynamic supply voltage can be configured to be dependent upon a variable reference voltage or to be dependent upon a variable reference current or both, as desired. To implement a dynamic supply voltage, circuit elements can be used that will vary based upon process and environmental changes. In this way, integrated circuit designs can avoid the use of a constant supply voltage that satisfies all expected process and environmental variations because the use of such a constant supply voltage will tend to cause more current and power to be consumed that is necessary to achieve desired operational speeds under typical process and environmental conditions.
It is noted that the reference bias current (IBIAS) can be programmably selected and chosen so as to set the initial operating point of the dynamic supply voltage used for biasing the circuit blocks. As such, this reference bias current (IBIAS) can be programmable in order to account for different operating conditions of the integrated circuit. In other words, a selection can be made from two or more bias current settings depending upon an expected operational application for the integrated circuit. In this way, an initial value for the supply voltage can be increased or decreased depending on the expected operational application for the circuit blocks being biased by the dynamic supply voltage. For example, a larger reference bias current (IBIAS) may be selected and programmed for a higher frequency VCO circuit whereas a lower reference bias current (IBIAS) may be selected and programmed for a lower frequency VCO circuit. After the reference bias current (IBIAS) is selected and programmed, the initial operating voltage of the dynamic supply voltage is set, and the dynamic supply voltage is then allowed to vary proportionally to temperature and process variations of the MOS transistors as to maintain a desired bias for the circuit blocks biased by this dynamic supply voltage. As such, the circuit can be biased with a different initial supply voltage depending upon the operational conditions for the integrated circuit. It is further noted that the reference bias current (IBIAS) will have some variation based upon the operational conditions for the integrated circuit even though these variations can be reduced with circuit techniques, calibration, and/or programmability.
Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in view of this description. It will be recognized, therefore, that the present invention is not limited by these example arrangements. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herein shown and described are to be taken as the presently preferred embodiments. Various changes may be made in the implementations and architectures. For example, equivalent elements may be substituted for those illustrated and described herein, and certain features of the invention may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the invention.
