Patent Abstract:
A system including an integrated circuit (IC) and a power supply regulator external to the IC. The IC operates in accordance with an active mode and a lower power mode, and is configured to retain a logical state during the low power mode. The power supply regulator is configured to i) supply a first voltage potential to a first pin of the IC during the active mode, and ii) disable the first voltage potential during the low power mode. The IC is configured to provide a first feedback signal from an internal supply of the IC to the power supply regulator via the first pin.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/284,524, filed Sep. 23, 2008, which is a continuation of U.S. patent application Ser. No. 10/620,470 (now U.S. Pat. No. 7,428,649), filed Jul. 15, 2003. The disclosures of the above applications are incorporated herein by reference in their entirety. 
    
    
     As memory arrays and other circuit blocks are embedded into the microprocessors that are used in a diversity of consumer products, the trend toward portable products suggests conserving power by lowering the operating voltage of the electronic devices. Additionally, process scaling is used to reduce the area needed for the memory array and logic functions in an effort to lower the product costs. However, process scaling poses problems since scaling oxide thickness and channel lengths may result in high leakage currents and consequent high standby power consumption. As the process is scaled, of particular importance is the thin gate-oxide of transistors used in memories, latches and logic used to store state values since leakage may be mitigated in other circuits by collapsing the supply voltages. 
     The thin gate-oxides may cause large drain-to-source currents and gate leakage currents that may be appreciable during a standby mode. Thus, there is a continuing need for better ways to provide flexibility for operating a microprocessor, memory or other circuit having thin gate-oxides while preserving low standby currents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
         FIG. 1  illustrates features of the present invention incorporated into a wireless communications device; 
         FIG. 2  illustrates an embodiment using power supply clamp transistors for gating the power supply to limit standby power in accordance with the present invention; 
         FIG. 3  illustrates a tri-state buffer for controlling the power supplied to an integrated circuit; 
         FIG. 4  illustrates a transistor and diode for controlling the power supplied to an integrated circuit; and 
         FIG. 5  is a schematic showing external power supply clamp transistors for gating the power supply to limit standby power in an integrated circuit in accordance with the present invention. 
     
    
    
     It will be appreciated that for simplicity and clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements. 
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled 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 so as not to obscure the present invention. 
     In the following description and claims, the terms “coupled” and “connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, “connected” may be used to indicate that two or more elements are in direct physical or electrical contact with each other. “Coupled” may mean that two or more elements are in direct physical or electrical contact. However, “coupled” may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. 
     The architecture shown in  FIG. 1  for wireless communications device  10  includes features of the present invention that may be used in a product designed for low power. The simplified diagram for a hand-held wireless communications device  10  shows a super heterodyne receiver  20  that receives a modulated signal from an antenna  30 , although this is not a limitation of the present invention. Alternate embodiments may include a direct conversion receiver. Further embodiments may incorporate multiple antennas for diversity. 
     A Low Noise Amplifier (LNA)  40  amplifies the signal received from antenna  30  and a mixer circuit  50  “mixes” a tone generated by an oscillator circuit with the received signal for down-converting the carrier frequency of the modulated signal to a baseband frequency. The baseband signal may be filtered through a filter  60  and converted to a digital value by an Analog-To-Digital Converter (ADC)  70 . A baseband and application processor  90  is connected to the transceiver to provide, in general, the digital processing of the received data within communications device  10 . Receiver  20  and associated analog circuitry may be embedded with processor  90  as a mixed-mode integrated circuit. Alternatively, receiver  20  may be incorporated as a stand-alone Radio Frequency (RF) integrated circuit that provides processor  90  with baseband signals. 
     The architecture presented for wireless communications device  10  may be used in a variety of applications, with the claimed subject matter incorporated into microcontrollers, general-purpose microprocessors, Digital Signal Processors (DSPs), Reduced Instruction-Set Computing (RISC), Complex Instruction-Set Computing (CISC), among other electronic components. In particular, the present invention may be used in laptop computers, smart phones, communicators and Personal Digital Assistants (PDAs), medical or biotech equipment, automotive safety and protective equipment, automotive infotainment products, and entertainment centers and multimedia networking systems that provide streaming audio and video applications in the home. However, it should be understood that the scope of the present invention is not limited to these examples. 
     A memory device  100  may be connected to processor  90  to store data and/or instructions used by processor  90 . In some embodiments, memory device  100  may be a volatile memory such as, for example, a Static Random Access Memory (SRAM), a Dynamic Random Access Memory (DRAM) or a Synchronous Dynamic Random Access Memory (SDRAM), although the scope of the claimed subject matter is not limited in this respect. In alternate embodiments, the memory devices may be nonvolatile memories such as, for example, an Electrically Programmable Read-Only Memory (EPROM), an Electrically Erasable and Programmable Read Only Memory (EEPROM), a flash memory (NAND or NOR type, including multiple bits per cell), a Ferroelectric Random Access Memory (FRAM), a Polymer Ferroelectric Random Access Memory (PFRAM), a Magnetic Random Access Memory (MRAM), an Ovonics Unified Memory (OUM), a disk memory such as, for example, an electromechanical hard disk, an optical disk, a magnetic disk, or any other device capable of storing instructions and/or data. However, it should be understood that the scope of the present invention is not limited to these examples. 
     Processor  90  includes a V CC  pin  130  for receiving a voltage potential from a power supply regulator  110 . The conditioned and regulated voltage potential may be passed through circuits  120  and  140  to provide a high quality internal V CC  voltage potential used by circuitry such as, for example, a memory cache, shadow latches, and other state-retentive logic blocks. As shown, the power supply circuitry may be off-die to allow improved power performance such as a low IR drop, reduced ripple, smaller die size and lower product costs. Circuit  140  provides external power supply clamp transistors that gate the power supply to limit standby power in the low standby power mode. The features of the present invention provide a circuit technique for state elements to enter and exit low standby leakage current modes on high performance and high leakage processes. Thus, integrated circuit state may be moved into an on-die low leakage storage, and then, power to combinational circuitry may be disabled externally in accordance with features of the present invention. While circuits  120  and/or  140  may disable or collapse the voltage potential supplied at pin  130  to the combinational circuitry, the voltage potential supplied to pin  150  may provide power to the low leakage memory or shadow latches. 
       FIG. 2  illustrates power supply regulator  110  generating a voltage potential that is provided via a trace on a circuit board to a V CC  pin  130  of an integrated circuit. The circuit board trace includes an inductance L and capacitors C, along with resistive impedance from the metal trace that provides an IR voltage drop. The on-die clamps  140  may be gated off when the integrated circuit is selected to operate in a low power mode. By way of example, the integrated circuit may be processor  90  that operates in an “ultra-drowsy” mode where the logical state of the integrated circuit is retained in low leakage devices while the supply V CC  (internal) is allowed to collapse. On the other hand, the on-die clamps  140  are gated on when processor  90  operates in the active mode. In one embodiment a REGULATOR FEEDBACK signal may be supplied from device pin  130  back to power supply regulator  110 . However, in this embodiment the IR drop through the CMOS clamps  140  is not compensated. In another embodiment, an OPTIONAL REGULATOR FEEDBACK signal may be supplied from an internal V CC  supply to provide a Kelvin sense that compensates for the IR drop. Note that when on-die clamps  140  are cutoff the regulator may be disabled and switch to receiving feedback at pin  130 . 
     Although only one V CC  pin  130  is illustrated in the figure it should be understood that supply regulator  110  may supply power to multiple V CC  pins  130 , with the various V CC  pins connected to separate blocks within the integrated circuit. For instance, one V CC  pin  130  may be connected to an internal arithmetic logic unit, another V CC  pin  130  may be connected to the input/output (I/O) pad ring, while yet another V CC  pin  130  may be connected to the main clock generator block, although these examples do not limit the scope of the present invention. Further, in addition to the V CC  pins  130  that may be connected to the various blocks within the integrated circuit and gated on and off, supply regulator  110  may supply a non-gated voltage potential through a separate pin  150  (see  FIG. 1 ) to “shadow” latches for state retention. 
       FIG. 3  illustrates features of the present invention for controlling the power of an integrated circuit. This embodiment includes a P-channel transistor  310  and an N-channel transistor  320  at the output of power supply regulator  110  that may be tri-stated as the integrated circuit enters the low power state. It is undesirable to force power supply regulator  110  to drive the output to zero volts on the V CC  supply in the low power state since the decoupling capacitances (the capacitors on the board) would be discharged, causing a substantial energy dissipation. The board capacitance is typically quite high, possibly  100 &#39;s of microfarads, in order to limit the supply ripple and provide good AC load line characteristics. Accordingly, P-channel transistor  310  and N-channel transistor  320  are tri-stated and the energy stored by the capacitors is dissipated via core leakage. Since leakage dissipates the capacitor charge slowly, the core may return quickly from the low power state because less charge (energy) needs to be delivered to V CC  to restore its voltage and allow operation if charge remains on the capacitors. It may also be possible to respond to an interrupt or other event at low voltage before restoring a full supply voltage for high-speed operation. 
     Note that it is inherently dangerous to open-circuit inductors, as high voltages may occur that may be deleterious to the integrated circuit. Consequently, the operation must take place at a carefully chosen time and operating point and the control laws of the feedback regulator must be properly accounted for. It should be noted that many other regulator configurations are possible and may also be used effectively without limiting features of the present invention. 
       FIG. 4  is another embodiment that illustrates features of the present invention for controlling the power of an integrated circuit. In this embodiment an off-die N-channel transistor  410  is connected to the output of power supply regulator  110  for supplying current to a node clamped by a diode  420 . A voltage potential is supplied to V CC  pin  130  from the common connection of the source of transistor  410  and the cathode of diode  420 . Transistor  410  may be gated off and the energy stored by the capacitors on the board may be dissipated via core leakage. 
       FIG. 5  is a schematic showing external power supply clamp transistors  510  for gating the power supply to limit standby power in an integrated circuit in accordance with the present invention. In this embodiment, external power supply clamp transistor(s)  510  are placed between power supply regulator  110  and the integrated circuit. Although clamp transistor(s)  510  are illustrated as complimentary devices that may handle additional power by the parallel transistors, it should be noted that some embodiments may use a single NMOS device for the clamp. 
     As before, supply regulator  110  may provide multiple, separate core supplies that may be externally clamped. When power supply regulator  110  supplies multiple core supplies though multiple clamps, a switching network may determine the feedback signal. The feedback signal, for example, may be determined by a supply which is on initially, or alternatively, by a supply which was on last. The feedback signal supplied to power supply regulator  110  may be transferred through a multiplexer  520 , with input signals received from a V CC  located internal on the core, the V CC  pin  130 , or external to the integrated circuit. Multiplexer  520  may be physically located on the board, in the integrated circuit or in power supply regulator  110 . Note that capacitance C 1  on the inside of clamp  510  maybe small, perhaps zero, so that the energy cost of a short standby interval is small and perhaps negligible. Since the feedback network does not carry substantial current, a higher resistance from the metal trace line can be tolerated. Again, the switching must obey the regulator control laws to avoid instability. 
     By now it should be apparent that a method and circuitry have been presented for gating the power supply to limit standby power in an integrated circuit. The IR drop through the clamps and trace metal may be compensated to improve power performance and allow the power supply regulator to supply the best quality power signals possible. 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Technology Classification (CPC): 8