# Patent

## Title
Apparatus and method for programmable power management in a programmable analog circuit block

## Abstract

An apparatus and method for programmable power management in a programmable analog circuit block. Specifically, the present invention describes an operational amplifier circuit that includes current sources that are coupled in parallel. Configuration bits are asserted to selectively enable or selectively disable one or more of the current sources in order to modulate the performance of the operational amplifier circuit block. Selective addition or removal of current sources increases or decreases the amount of current within the operational amplifier and, correspondingly, the speed and power consumption of the operational amplifier. Combinations of asserted configuration bits pass a bias voltage in order enable selected current sources. In one embodiment, the bias voltage can be increased in order to increase the current output of one of the current sources which, correspondingly, increases the speed of the operational amplifier circuit block.

## Background
RELATED U.S. APPLICATION
This application claims the benefit of U.S. Provisional Patent Application No. 60/243,708, filed Oct. 26, 2000.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of power management. More specifically, the present invention relates to the field of programmable power management in a programmable analog circuit containing an operational amplifier.
2. Related Art
A microcontroller is a highly integrated chip having all or most of the necessary components to control some process or aspect in a circuit. For example, the microcontroller typically includes a central processing unit (CPU), random access memory (RAM), read only memory (ROM), input/output (I/O) interfaces, timers, and interrupt controller. The typical microcontroller has bit manipulation instructions, easy and direct access to I/O interfaces, and quick and efficient interrupt processing. By including only features specific to the task of the microcontroller and integrating the functionality onto a single chip, the cost to produce the microcontroller can be drastically reduced.
Programmable analog circuit designs for microcontrollers allow a user limited programmability to vary circuit parameters or the underlying topology of the programmable analog circuit. For example, a programmable analog circuit may be comprised of interconnected analog blocks set in a fixed topology that has programmable parameters, such as filter bandwidth or roll-off, that can be set and changed according to application needs. While the signal processing path and basic functionality of the analog circuit remains unchanged, some programmable functionality is introduced by letting parameters vary in the programmable analog circuit.
A particular functionality important to programmable analog circuit designs is power management. Power management is particularly important in light of the movement towards higher levels of integration, and higher circuit densities. Programmable analog circuit blocks include basic programmable operational amplifier circuits used for many functionalities including gain amplifiers, switch capacitor integrators, analog to digital (A/D) converters, digital to analog (D/A) converters, filters, etc. In addition, a switched capacitor integrator forms the basis for an analog processing unit that can support A/D and D/A digital converters, comparators, programmable gain amplifiers, and filters.
As end products become more lightweight, smaller, and more portable, the microcontrollers operating at three volts and lower allow for less power consumption and longer battery life. However, in the past, designing the proper analog circuitry for lower power consumption was difficult to achieve without sacrificing operating performance. As a result, microcontrollers previously offered nonexistent or limited power management functionality.
FIG. 1 is a circuit diagram of the prior art illustrating a typical operational amplifier circuit used in analog circuits. Current sources 110 are biased with a bias voltage (not shown) in order to provide current to the operational amplifier circuit 100 that drives the output voltage and corresponding power coming out of the node 120. A compensation capacitor may be coupled between the nodes 120 and 130, and forms part of the load being driven by the operational amplifier circuit 100.
The current sources 110 are non-adjustable or not programmable. In the design illustrated in FIG. 1, the current sources are an unchangeable element in the output voltage and power shown at the node 120. As a result, there is no programmable power management in the current sources 110 for the operational amplifier circuit 100. For instance, the operational amplifier circuit 100 would consume the same amount of power irrespective of the load being driven.
One method implemented in the past for controlling power management throughout a programmable analog circuit included increasing or decreasing the bias voltage (not shown in FIG. 1). The bias voltage drives the operational amplifier circuit 100 in an programmable analog block. Increasing the bias voltage does increase the speed of the operational amplifier circuit 100 and the overall circuit; however, the improvement comes at a cost of performance.
Increasing the bias voltage increases the current through the operational amplifier in the programmable analog circuit. More current increases the slew rate of the programmable analog block and increases the operational amplifiers ability to drive the capacitor representative of the load. This allows the operational amplifier to run faster resulting in better performance.
However, there is a tradeoff. By increasing the bias voltage, the dynamic range of the operational amplifier is reduced. Basically, the dynamic range of output voltage at node 120 is clipped or reduced for the programmable analog block containing the operational amplifier. As a result, increasing the bias voltage negatively decreases the dynamic range of the block containing the operational amplifier.
Conversely, to maintain the dynamic range of the programmable analog block, the bias voltage (not shown) must be reduced. However, at the lower bias levels (and hence lower bias voltages, such as, three volts), the circuit containing the operational amplifier operates at much slower speeds.
Thus, a need exists to provide a degree of programmability to power management in a programmable analog circuit. Another need exists to provide increased speeds in a programmable analog circuit without sacrificing performance.
SUMMARY OF THE INVENTION
The present invention discloses a method and system for power management in a programmable analog circuit. The present invention provides for a degree of programmability in the management of power in a programmable analog circuit. Also, the present invention meets the above need and provides for increased speeds in a programmable analog circuit without sacrificing performance.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments which are illustrated in the various drawing figures.
Specifically, one embodiment of the present invention describes a programmable analog block containing an operational amplifier circuit that includes a plurality of current mirrors or sources that are coupled in parallel. Configuration bits are asserted to selectively enable or selectively disable one or more of the current sources in order to modulate the performance of the operational amplifier circuit block. Selective addition or removal of current mirrors increases or decreases the amount of current within the operational amplifier and, correspondingly, the amount of power consumed for the operational amplifier and the speed of the operational amplifier.
Various combinations of asserted configuration bits pass a bias voltage in order to enable different groups of selected current mirrors. The selected current mirrors come from the plurality of available current sources in the operational amplifier.
Selectively enabling and disabling various current mirrors in the plurality of current sources allow for power adjustment of the programmable analog block containing an operational amplifier. Enabling a current source increases the current through the operational amplifier in order to increase the operating speed of the operational amplifier. As a result, this increases the power consumed by the operational amplifier. Correspondingly, disabling a current source decreases the current through the operational amplifier, decreases the operating speed of the operational amplifier, and decreases the power consumed by the operational amplifier. Enabling or disabling the current mirrors within the programmable analog block does not deleteriously affect the dynamic swing of the operational amplifier contained within the programmable analog block as the external bias voltage is not changed.
In one embodiment, the bias voltage can be further increased in order to further increase the current output of one of the current sources in a selected group of current sources. This increased current increases the operating speed of the operational amplifier circuit block. In another embodiment, the bias voltage is successively increased to successive current sources in a scaleable ratio in order to provide scaleable increases in the operating speed of the operational amplifier.
In another embodiment of the present invention, a microcontroller controls the programmable management of power through the programmable analog circuit.



BRIEF DESCRIPTION OF THE DRAWINGS
PRIOR ART FIG. 1 is a block diagram of an exemplary operational amplifier circuit without any programmable power management capabilities.
FIG. 2 is a logical block diagram of an exemplary microcontroller computer system, in accordance with an embodiment of the present invention.
FIG. 3 illustrates a block diagram of an exemplary operational amplifier programmable analog circuit block with programmable power management, in accordance with one embodiment of the present invention.
FIG. 4A illustrates a circuit diagram of an exemplary logic decoder from an operational amplifier programmable analog circuit with programmable power management, in accordance with one embodiment of the present invention.
FIG. 4B illustrates a circuit diagram of an exemplary multiplexor from an operational amplifier programmable analog circuit with programmable power management, in accordance with one embodiment of the present invention.
FIG. 4C illustrates a circuit diagram of an exemplary operational amplifier from an operational amplifier programmable analog circuit with programmable power management, in accordance with one embodiment of the present invention.
FIG. 5 illustrates a truth table of the programmable analog circuit block with programmable power management, in accordance with one embodiment of the present invention.
FIG. 6 is a flow diagram illustrating steps in a computer implemented method for programmable power management in a programmable analog circuit block, in accordance with an embodiment of the present invention.



DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the preferred embodiments of the present invention, a method and system for programmable power management in a programmable analog circuit block, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Notation and Nomenclature
Some portions of the detailed descriptions which follow are presented in terms of procedures, steps, logic blocks, processing, and other symbolic representations of operations on data bits that can be performed on computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, computer executed step, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “accessing,” or “processing,” or “computing,” or “translating,” or “calculating,” or “determining,” or “scrolling,” or “displaying,” or “recognizing,” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Referring now to FIG. 2, portions of the present invention are comprised of computer-readable and computer-executable instructions which reside, for example, in computer-readable media of an electronic system, such as a microcontroller. FIG. 2 is a block diagram of exemplary interior components of an exemplary electronic system 200, which includes a microcontroller 210, upon which embodiments of the present invention may be implemented. It is appreciated that the exemplary microcontroller 210 of FIG. 2 is only exemplary and that the present invention can implement a number of different electronic systems including modems, digital to analog (D/A) converters, analog to digital (A/D) converters, power gain amplifiers, comparators, switched capacitor filters, and the like.
FIG. 2 illustrates circuitry of an exemplary computer system 200 which includes a microcontroller 200. Exemplary microcontroller 200 includes an internal address/data bus 220 for communicating information, a central processor 201 coupled with the bus 220 for processing information and instructions, a volatile memory 202 (e.g., random access memory (RAM), static RAM dynamic RAM, etc.) coupled with the bus 220 for storing information and instructions for the central processor 201, and a non-volatile memory 203 (e.g., read only memory (ROM), programmable ROM, flash memory, EPROM, EEPROM, etc.) coupled to the bus 220 for storing static information and instructions for the processor 201.
With reference still to FIG. 2, an optional signal Input/Output device 208 which is coupled to bus 220 for providing a communication link between microcontroller 210 and a network environment is described. As such signal Input/Output (I/O) device 208 enables the central processor unit 201 to communicate with or monitor other electronic systems or analog circuit blocks that are coupled to the microcontroller 210.
The input/output device 208 could be a I/O interface such as a serial or USB port that is associated with the bus 220. Data from the microcontroller 210 travels through the port and onto an external bus 230 that provides for data transfer between components of the electronic system 200, including microcontroller 210. In one embodiment of the present invention, external bus 230 can be a serial communication bus, such as the serial peripheral interface (hereinafter referred to as “SPI”) communication bus.
For example, components of electronic device 200 could include a display device 205 coupled to the bus 230 for displaying digital images to the user. The display device 205 utilized with electronic device 200 may be a liquid crystal display (LCD) device, a cathode ray tube (CRT), a field emission display device (also called a flat panel CRT), or other display device suitable for generating graphic images and alphanumeric characters recognizable to the user.
Also included in electronic device 200 is an optional alphanumeric input device 206, in another embodiment of the present invention. Alphanumeric input device 206 can communicate information and command selections to processor 201 via bus 230 and bus 220. In one implementation, alphanumeric input device 206 is a touch screen device. Alphanumeric input device 206 is capable of registering a position where contact is made.
In still another embodiment of the present invention, electronic device 200 also includes an optional cursor control or directing device (on-screen cursor control 207) coupled to bus 230 for communicating user input information and command selections to processor 201. In one implementation, on-screen cursor control device 207 is a touch screen device incorporated with display device 205.
Programmable Power Management of a Programmable Analog Circuit
This disclosure describes an apparatus and method for programmable power management in a programmable analog circuit block. Referring now to FIG. 3, a programmable analog circuit block 300 is shown that acts as an operational amplifier, in accordance with one embodiment of the present invention. Operational amplifier circuits can be used to implement numerous functionalities, such as D/A converters, A/D converters, power gain amplifiers, comparators, switch capacitor filters, etc. A plurality of current sources are contained within circuit block 300.
The plurality of current sources provide a scaleable and incremental source of current for the operational amplifier contained within the circuit block 300. Each additional current source provides additional current to the operational amplifier in circuit block 300. The increase in current to the operational amplifier correspondingly increases the speed of the operational amplifier, the output voltage and output power exhibited at node 340, and the power consumed by the operational amplifier in circuit block 300.
Furthermore, selective enablement of different combinations of current sources allows for the adjustment of power consumption and performance capability of the operational amplifier contained within the analog circuit block 300. This, in turn, allows for programmable power management of the analog circuit block 300 by a microcontroller, such as microcontroller 200.
Additionally, the increase in performance of the operational amplifier is not accomplished by increasing the bias voltage (not shown). Instead, the addition of parallel current sources (e.g., sources 310, 315, 320, 325, 330, and 335) provides increased current through the operational amplifier and increases the speed and power output of the operational amplifier at the node 340. As a result, the increased performance comes without any of the deleterious effects on the dynamic range of the operational amplifier contained within the analog circuit block 300. This allows for increased performance, namely speed of the operational amplifier, of the programmable analog block 300 at lower bias dad voltages and lower bias voltages.
The parallel current sources allow the programmable analog block 300 to operate at faster speeds at low bias voltages, and at lower power levels. Since the programmable analog block 300 is driven by a lower bias voltage, the dynamic range of the block 300 is higher. Also, the addition of parallel current sources increases the speed through the operational amplifier contained in block 300 thereby increasing the slew rate for overcoming the load capacitance, and increasing the operating speed of the operational amplifier.
Although embodiments of the present invention are described using current mirrors or current sources, the present invention is well suited to other embodiments where other types of power sources or mirrors are utilized.
In one embodiment of the present invention, the current sources are paired together, as paired current mirrors. One of each pair of current mirrors is coupled to the transistors coupled to the input voltages at node 350 (−Vin) and node 355 (+Vout), and the other of each pair is coupled to the output voltage at node 340. The current mirrors coupled to the transistors at the input voltages at nodes 350 and 355 are coupled in parallel. In addition, the current mirrors coupled to the output voltage at node 340 are coupled in parallel fashion.
For example, FIG. 3 shows three pairs of current mirrors in analog circuit block 300. The first pair of current mirrors contains current source PB1 310 and current source PB1A 315. The second pair of current mirrors contains current source PB2 320 and current source PB2A 325. The third pair of current mirrors contains current source PB3 330 and current source PB3A 335. The current mirrors in each pair are enabled and disabled in similar fashion.
In one embodiment of the present invention, for each pair of current mirrors, the current source coupled to the output voltage at node 340 outputs an integer multiple (e.g., two times) of the amount of current for its corresponding current source in the pair that is coupled to the transistors at the input voltages at nodes 350 and 355. For example, in the first pair of current sources, current source PB1A 315 outputs twice the amount of current as current source PB1 310.
In addition, a source voltage (VCC) is coupled to node 360 for the operational amplifier in circuit block 300. Another source voltage (VSS) is coupled to node 370 for the operational amplifier in circuit block 300.
The operational amplifier circuit 300 as shown in FIG. 3 is exemplary only. Although three pairs of current sources are shown in FIG. 3, the present invention is also well suited to an embodiment which can accommodate less or more pairs of current sources to provide further incremental programmable control over the analog circuit block 300.
In another embodiment of the present invention, the paired current mirrors provide further incremental increases in the current through the operational amplifier contained within the circuit block 300. This is accomplished by turning on selected current mirrors.
Each of the current mirrors supply varying amounts of current depending on the number of devices contained within the current mirror. For example, a scaleable current ratio of one to four to twelve (1:4:12) is envisioned in one embodiment of the present invention. The same bias voltage is presented to each of the current mirrors; however, each of the current mirrors contain a certain number of identical devices that are in ratio to the other current mirrors. For example, the third pair of current mirrors (e.g., sources PB3 330 and PB3A 335) has 12 identical devices and supplies twelve times the current supplied by the first pair of current mirrors. The second pair of current mirrors (e.g., sources PB2 320 and PB2A 325) has four identical devices and supplies four times the current supplied by the first pair of current mirrors. Correspondingly, the first pair of current mirrors (e.g., sources PB1 310 and PB1A 315) has one device.
For example, a scaleable ratio or multiple of one to four to twelve (1:4:12) is envisioned in one embodiment. In this case, the third pair of current mirrors (e.g., sources PB3 330 and PB3A 335) would see twelve times the bias voltage (VPB as illustrated in FIG. 4A), and correspondingly provide approximately twelve times the current as from the first pair of current mirrors. The second pair of current mirrors (e.g., sources PB2 320 and PB2A 325) would see four times the bias voltage (VPB as illustrated in FIG. 4A) and correspondingly provide approximately four times the current to the operational amplifier in circuit block 300 as from the first pair of current mirrors. No boosting of the bias voltage (VPB in FIG. 4A) is presented to the first pair of current mirrors (e.g., sources PB1 310 and PB1A 215).
Implementation of the programmable power management in the analog circuit block 300 that acts as an operational amplifier is achieved by selectively removing or including each of the paired current mirrors. At full power, or the maximum speed of the operational amplifier in block 300, all the paired current mirrors (e.g., sources 310, 315, 320, 325, 330, and 335) are coupled to the operational amplifier in the circuit block 300. At minimum power, or the minimum speed of the operational amplifier 310, only the first pair of current mirrors (e.g., sources 310 and 315) are provided without boosting the bias voltage (VPB as shown in FIG. 4A). The rest of the current mirrors are decoupled from operational amplifier in the analog circuit block 300.
As such, incremental increases in speed and power consumption through the analog circuit block 300 is achieved by selecting one or more of pairs of current mirrors in FIG. 3, in accordance with one embodiment of the present invention.
Although a ratio of one to four to twelve (1:4:12) is recited in the present embodiment, the present invention is also well suited to an embodiment in which other ratios or integer multiples are used, and/or a varying number of current mirrors are used to give incremental local power management of the operational amplifier in circuit block 300.
FIG. 4A illustrates a circuit diagram of an exemplary circuit with programmable power management capabilities. Selection of the current sources driving the operational amplifier in the programmable analog circuit block as shown in FIGS. 4A, 4B, and 4C, is accomplished by asserting configuration bits, in accordance with one embodiment of the present invention. FIG. 4A shows two configuration bits that can be asserted in combination, the S0 configuration bit 410 and the S1 configuration bit 420. The various combinations allowed in selecting between the two configuration bits controls three pairs of current sources for the programmable analog block. A truth table 500 of FIG. 5 illustrates the various combinations of the configuration bits 410 and 420.
The programmable analog circuit block as illustrated in FIGS. 4A, 4B, and 4C can be comprised of three elements: a logic decoder, a multiplexor, and an operational amplifier. FIG. 4A is a circuit diagram of the logic decoder 400. FIG. 4B is a circuit diagram of the multiplexor 402. FIG. 4c is a circuit diagram of the operational amplifier 404.
Returning to FIG. 4A, the two configuration bits (e.g., S0 410 and S1 420) are inputs into the logic decoder 400. The function of the logic decoder 400 is to generate various signal outputs according to the assertion of configuration bits (e.g., S0 410 and S1 420). The various output signals generated from the logic decoder 400 include, but are not limited to the following output voltage signals: S0b at node 450, S1b at node 452, S2 at node 454, and S2b at node 456.
Depending on the various configuration bits asserted, the various output voltage signals (e.g., S0b, S1b, S2, and S2b) from the logic decoder 400 are inputted into the multiplexor 402 of the programmable analog circuit block. In accordance with the present embodiment, the four to one (4 to 1) multiplexor 400 is implemented to select between the various output signals. The function of the multiplexor 402 is either to pass the bias voltage (VPB) 460 on to the pairs of current sources, or to isolate the bias voltage (VPB) 460 and shut down the pairs of current sources.
As shown in FIG. 4B, the multiplexor 402 has three voltage output signals: VPB-1 at node 470, VPB-2 at node 480, and VPB-3 at node 490. The three voltage output signals (e.g., VPB-1, VPB-2, and VPB-3) each provide a bias voltage that is taken from the bias voltage (VPB 460) to one of the three pairs of current sources driving the operational amplifier circuit 404 as shown in FIG. 4C. In one embodiment, each of the voltage output signals (e.g., VPB-1, VPB-2, and VPB-3) are identical to the bias voltage (VPB 460).
For example, the bias voltage VPB-1 at node 470 drives the pair of current sources 472 and 474. The bias voltage VPB-2 at node 480 drives the pair of current sources 482 and 484. Finally, the bias voltage VPB-3 at node 490 drives the pair of current sources 492 and 494. As discussed previously, each of the pairs of current sources contain varying numbers of identical devices that affect the current output for that pair of current sources.
As illustrated in FIG. 4C, each of the bias voltages (e.g., VPB-1, VPB-2, and VPB-3) control both current sources in each of the pairs of current sources. As such, if VPB-1 is presented at node 470, then both current sources 472 and 474 of the pair of current sources are enabled and provide current to the operational amplifier circuit 404.
The operational amplifier circuit 404 as shown in FIG. 4C also has an input voltage at nodes 495 and 496. The output voltage for the operational amplifier circuit 404 and the programmable analog circuit block is taken at node 497.
As discussed previously, the bias voltages (e.g., VPB-1, VPB-2, and VPB-3) can be incremented to provide a scaleable increase of speed or power consumption in the operational amplifier 404. For example, the input bias line VPB 460 can be set to another voltage. Combined with the programming bits (e.g., S0 and S1), six levels of bias can be achieved, in contrast to only three levels of bias when the bias voltage VPB 460 stays constant.
In addition, selection of the pairs of current mirrors can provide a scaleable increase of speed or power consumption in the operational amplifier 404. For example, a ratio of supplied currents from each of the current mirrors is dependent on the number of devices contained within the current mirrors that are controlled by the bias voltages (e.g., VPB-1, VPB-2 and VPB-3). Bias voltage VPB-1 controls the pair of current mirrors 472 and 474. Bias voltage VPB-2 controls the pair of current mirrors 482 and 484. Bias voltage VPB-3 controls the pair of current mirrors 492 and 494. In one embodiment, the ratio of currents can be one to four to twelve (1:4:12).
The truth table 500 of FIG. 5 describes the performance modulation of the analog circuit block illustrated in FIGS. 4A, 4B, and 4C. Selection of the configuration bits S0 and S1 in various combinations selectively enable and disable the pairs of current mirrors available to the operational amplifier circuit 404 of FIG. 4C.
For example, as exhibited in line 510, if both configuration bits S0 and S1 were not asserted, then all the pairs of current mirrors would be disabled. This would effectively shut off the operational amplifier 404 controlled by truth table 500. Additionally, as exhibited in line 520, if only the S1 bit were asserted at node 420, then the bias voltage VPB-1 would be presented at node 470 for the pair of current mirrors 472 and 474.
Further, as exhibited in line 530 of Table 500, if only configuration bit S0 were asserted at node 410, then two pairs of current sources would be enabled. The bias voltage VPB-1 at node 470 would be presented, thus turning on the pair of current mirrors 472 and 474. Also, the bias voltage VPB-2 at node 480 would be presented, thus turning on the pair of current mirrors 482 and 484.
Lastly, as exhibited in line 540 of Table 500, both configuration bits S0 and S1 were asserted at nodes 410 and 420, respectively, then all pairs of current mirrors would be enabled. For instance, the bias voltage VPB-1 at node 470 would be presented, thus turning on the pair of current mirrors 472 and 474. Also, the bias voltage VPB-2 at node 480 would be presented, thus turning on the pair of current mirrors 482 and 484. Additionally, the bias voltage VPB-3 at node 490 would be presented, thus turning on the pair of current mirrors 492 and 494.
It is appreciated that Table 500 is exemplary only. The present invention is well suited to embodiments in which varying numbers of configuration bits are available driving a varying number of current sources to provide additional power adjustment of the operational amplifier 404 of the analog circuit block as illustrated in FIGS. 4A, 4B, and 4C.
A microcontroller, such as microcontroller 200 of FIG. 2, could control the power management functionality over the programmable analog circuit illustrated in FIGS. 4A, 4B, and 4C, in accordance with one embodiment of the present invention. The microcontroller 200 could implement the truth table 500 for providing programmable power management.
FIG. 6 illustrates a flow chart 600 of steps for process 600 showing the programmable power management of a programmable analog circuit, in accordance with an embodiment of the present invention. It is appreciated that process 600 incorporates the previous apparatus description in method form.
The present embodiment begins with step 610 where a first combination of configuration bits is asserted. The first combination is selected from a plurality of configuration bits. For example, two configuration bits, as shown in FIGS. 4A, 4B, and 4C, can control three pairs of current sources.
In step 620, the present embodiment sends a bias signal in response to the first combination of configuration bits. The bias signal is a bias voltage supplied to the operational amplifier in the programmable analog circuit. The bias signal is sent to a selected group of current sources in the operational amplifier, as dictated by the first combination of configuration bits. The current sources are coupled in parallel.
In step 630, the present embodiment enables the selected group of current sources in order to adjust the power consumption and performance of the operational amplifier in the programmable analog circuit block. Selectively enabling or disabling the various current sources driving the operational amplifier provides selection between various speeds and power consumption in relation to the performance of the operational amplifier. The various combinations of asserting configuration bits select between the various speeds and power consumption that relate to the performance of the operational amplifier in the programmable analog circuit block.
While the methods of embodiments illustrated in process 600 show specific sequences and quantity of steps, the present invention is suitable to alternative embodiments. For example, not all the steps provided for in the method are required for the present invention. Furthermore, additional steps can be added to the steps presented in the present embodiment. Likewise, the sequences of steps can be modified depending upon the application.
The preferred embodiment of the present invention, programmable power management in a programmable analog circuit, is thus described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.

## Claims

1. A programmable analog circuit block having programmable power management comprising:
an operational amplifier circuit for driving a load;
a plurality of paired current sources located within said operational amplifier circuit, wherein a first current source in each pair is coupled in a first parallel configuration to a first node that is coupled to transistors receiving input voltages to said operational amplifier circuit, and a second current source in each pair is coupled in a second parallel configuration to an output of said operational amplifier circuit, wherein a ratio of the amount of current between said current sources of each pair of current sources is proportionally equal;
a bias supply signal for generating a given bias voltage; and
a plurality of configuration bits for selectively applying said given bias voltage to an associated pair of current sources in order to modulate the performance of said operational amplifier circuit.

2. The programmable analog circuit block as described in claim 1, wherein said plurality of paired current sources comprises a first and a second pair of current sources.

3. The programmable analog circuit block as described in claim 2, wherein said second pair of current sources provides twice the amount of current in said operational amplifier as said first pair of current sources.

4. The programmable analog circuit block as described in claim 1, further comprising:
a logic decoder for generating a plurality of select signals from said plurality of configuration bits; and
a multiplexor for selectively applying said given bias voltage to said associated pair of current sources based on said plurality of select signals.

5. The programmable analog circuit block as described in claim 4, wherein a voltage level for said bias voltage is increased in order to increase current output from said plurality of current sources.

6. The programmable analog circuit block as described in claim 1, wherein current provided from each pair of current sources is increased by a scaleable ratio to provide scaleable increases in speed of said operational amplifier.

7. The programmable analog circuit block as described in claim 1, wherein a voltage for said bias supply signal is increased for each of said plurality of current sources to increase speed of said operational amplifier.

8. A programmable analog circuit block having programmable power management comprising:
an operational amplifier circuit for driving a load;
a plurality of paired current sources contained within said operational amplifier circuit for increasing current within said operational amplifier circuit, wherein a ratio of the amount of current between current sources of each pair of current sources is proportionally equal;
a bias supply signal for biasing said plurality of paired current sources; and
a plurality of configuration bits for selectively applying said bias supply voltage to one or more of said plurality of paired current sources, based upon a current state of the configuration bits, in order to modulate performance of said operational amplifier circuit.

9. The programmable analog circuit block as described in claim 8, wherein each of said plurality of paired current sources further comprise:
a first current source coupled to a first node that is coupled to transistors receiving an input voltage to said operational amplifier circuit, wherein all first current sources in said plurality of paired current sources are coupled in parallel; and
a second current source coupled to a second node associated with an output voltage to said operational amplifier circuit, wherein all second current sources in said plurality of paired current sources are coupled in parallel.

10. The programmable analog circuit block as described in claim 8, wherein each of said plurality of paired current sources increase current within said operational amplifier in order to increase the speed of said operational amplifier circuit.

11. The programmable analog circuit block as described in claim 8, further comprising:
a logic decoder for generating a plurality of select signals based on said current combination of configuration bits; and
a multiplexor for selectively applying said bias supply voltage to said one or more pairs of current sources based on said plurality of select signals.

12. A method of performing programmable power management in a programmable analog block comprising the steps of:
a) asserting a first group of configuration bits from a plurality of configuration bits; and
b) sending a bias voltage signal, in response to said first group of configuration bits, to a selected group of paired current sources from a plurality of paired current sources in an operational amplifier wherein each configuration bit enables an associated pair of current sources from said plurality of paired current sources and wherein a ration of the amount of current between current sources coupled to an input stage and output stage of said operational amplifier respectively of each pair of current sources is proportionally equal.

13. The method as described in claim 12, wherein said selected group of paired current sources is enabled to increase current in said operational amplifier to increase the operating speed of said operational amplifier.

14. The method as described in claim 12, wherein said method further comprises:
increasing said bias voltage to further increase the operating speed of said operational amplifier.

15. The method as described in claim 12, wherein said plurality of paired current sources are selectable to provide scaleable increases in operating speed for said operational amplifier.

16. The method as described in claim 12, wherein a first current source in each pair is coupled to a first node that is coupled to transistors receiving input voltages to said operational amplifier, and a second current source in each pair is coupled with an output voltage to said operational amplifier, wherein each first current source coupled to said input voltage is coupled in parallel, and wherein each second current source coupled to said output voltage is coupled in parallel.

17. The method as described in claim 16, further comprising the step of:
doubling current output in said second current source in comparison to said first current source of each of said plurality of paired current sources.

18. The method as described in claim 12, comprising the further step of:
disabling a remaining group of paired current sources to deny current to said operational amplifier in order to modulate performance of said operational amplifier, said selected group of paired current sources and said remaining group of paired current sources combined forming said plurality of paired current sources.