TEMPERATURE-BASED SWITCHED-MODE POWER SUPPLY

BACKGROUND OF THE INVENTION [0001] Field of the Invention

[0002] The present invention relates to adaptive power supply voltage regulation for integrated circuits to control leakage current. [0003] Description of the Related Art

[0004] As modern digital-process technologies advance to smaller geometry, even low-power (LP) integrated circuit (IC) design versions exhibit relatively large IDDQ leakage current when used to implement ICs having multi-million gate characteristics. IDDQ leakage current, also known as quiescent Idd or quiescent power-supply current, for ICs employing complementary metal-oxide semiconductor (CMOS) technology, refers to the steady-state current (current when all switching transients have settled) from the power supply to the CMOS circuitry, which, for the ideal case, should be zero static current. Leakage current in a defect-free circuit should be negligible, but a defect, such as a gate-oxide short circuit or a short circuit between metal lines, forms a conduction path from the power supply to ground that causes the circuit to dissipate relatively high current as leakage current. As geometry is reduced, the likelihood and number of such defects increases, causing an undesirable increase in IDDQ leakage current.

[0005] In addition, IDDQ leakage current varies with varying temperature of i) the IC and ii) the corresponding power source that drives the IC. For example, the leakage current drift when temperature increases from 25 C to 60 C is approximately 2-4 times increase in leakage current. Leakage current drift in an IC translates into battery current drift for a battery power source supplying power to the IC. Excessive battery current drift shortens battery life, which is undesirable for applications such as mobile phones or other common portable consumer electronics products. [0006] Many ICs employ a switched-mode power supply (SMPS) and voltage regulators, such as low drop-out linear regulators (LDOs), to alter the battery voltage employed to drive the core circuitry of the IC (e.g., the voltage applied to Vdd power rails). An SMPS is an electronic power supply unit (PSU) that incorporates a switching regulator, which is an internal control circuit with rapidly- switched power transistors (such as MOSFETs), employed to stabilize the output voltage or current. SMPSs may be used as replacements for linear regulators when higher efficiency, lower loss through heat, and smaller size are required. However, SMPSs have low power factors when compared to LDOs, and so a given design typically employs two-stage power/voltage regulation to obtain the benefits of both SMPSs and LDOs.

SUMMARY OF THE INVENTION

[0007] In one embodiment, the present invention allows for control of leakage current supplied from a power supply by monitoring a temperature of the power supply; generating an enable signal indicating whether the temperature of the power supply has reached a threshold, wherein the threshold is based on a temperature related to the leakage current supplied from the power supply to at least one of a voltage regulator and core circuitry; and coupling, based upon the enable signal, the power supply to the core circuitry either through i) a first stage and a second stage of the voltage regulator if the temperature of the power supply has reached the threshold or ii) through the second stage of the voltage regulator bypassing the first stage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements. [0009] FIG. 1 shows a block diagram of an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

[0010] In accordance with exemplary embodiments of the present invention described herein, temperature sensing is employed within a device to enable one or more modes of operation of a switched-mode power supply (SMPS) coupled between i) core circuitry of, for example, an integrated circuit (IC) and ii) a power source when threshold temperatures corresponding to the modes of operation are detected. A temperature-enabled SMPS might provide the advantage of reducing overall temperature drift of the IC device's standby current, providing a corresponding increase in power supply efficiency of, for example, a battery used to power the IC in a mobile phone, laptop computer, music player, gps, radio receiver, or other types of consumer electronics devices incorporating battery power.

[0011] FIG. 1 shows a block diagram of an exemplary embodiment of the present invention. System 100 includes core circuitry 101, power supply 102, voltage regulator 103, and temperature detector 104. Core circuitry 101 might be included in an IC and might comprise CMOS-based circuitry having temperature-varying IDDQ leakage current that leads to varying quiescent battery current. While the preferred embodiments of the present invention are described for CMOS-based circuitry, the present invention is not so limited and might be applied to other types of semiconductor

devices with temperature-varying leakage current.

[0012] Power supply 102 comprises battery 110 and temperature sensor 111. Battery 110 supplies power with output voltage V _bat - Temperature sensor 111, which might be implemented with a thermistor, provides output signal S _Temp , which might be the voltage across, or current through, the thermistor, that indicates a relative temperature of battery 110, IC core circuitry 101, and/or system 100.

[0013] Voltage regulator 103 comprises switch 120, switched-mode power supply (SMPS) 121, and low drop-out linear regulator (LDO) 122. Switch 120, based on signal EN, applies either the battery voltage V _bat or output voltage V _SMPS from SMPS 121 to LDO 122. SMPS 121 converts voltage V _bat of battery 110 to output voltage V _SMPS - LDO 122, in turn, regulates either i) the battery voltage V _bat or ii) the output voltage V _SMPS SO as to provide output voltage V _LDO that is employed to drive, for example, CMOS-based circuitry at voltage node Vic _∞re of core circuitry 101. While a single LDO 122 is shown in FIG. 1, one skilled in the art will realize that one or more LDOs might typically be employed in a given implementation, and, thus, LDO 122 of FIG. 1 represents a function that might be spread over many similar devices.

[0014] Temperature detector 104 comprises signal detector 130, which might be an analog-to- digital converter (ADC), and logic 131. Signal detector 130 receives signal S _Temp and samples the signal to provide a sampled, quantized signal S _T e _mP [n]. Logic 131 compares the signal S _T e _mP [n] to a specified threshold value, TH, and based on this comparison generates switch-enable signal EN when the threshold value TH is reached (e.g., when the threshold TH is met or exceeded). While the present invention is described with respect to comparison of the signal S _Temp [n] to a single threshold, the present invention might be extended to generate multiple enable signals based on multiple thresholds for control of, for example, multiple SMPSs. In addition, while the described exemplary embodiment shows sampling of the signal S _TemP and comparison to one or more thresholds in the digital domain, other implementations might simply use comparators in the analog domain to provide threshold-crossing information.

[0015] During low-power standby mode, core circuitry 101 is inactive and, for example, the temperature of battery 110 is approximately ambient or room temperature, around 25° C. During standby mode, switch 120 is in bypass mode (switch 120 is in position "1" and conducts so as to bypass SMPS 121). Battery voltage, V _bat , is applied to the LDO 122 that regulates the voltage V _bat to V _LDO - Voltage V _LDO , in turn, is applied to the ICs power supply rails as Vic _∞re to power core circuitry 101.

[0016] SMPS 121 is bypassed when system 100 is in low-power standby mode (when the circuitry is in an inactive mode) because, although less efficient with respect to power transfer, in standby mode, using LDO 122 to regulate power supply voltage is beneficial since current drawn by core circuitry 101 is negligible when not in operation, but SMPS 121, which might typically be implemented in CMOS technology, might typically exhibit relatively large IDDQ leakage current.

Thus, in bypass mode, SMPS 121 is not coupled to, and does not draw IDDQ leakage current from, battery 110. For one exemplary implementation, IDDQ leakage current of an SMPS might be on the order of 400 μA.

[0017] Once a battery-powered device is activated, however, power source/IC temperature is increased due to power consumption of the IC and, for example, chemical reaction in the battery supplying the power to the IC. Referring to FIG. 1, as temperature changes within system 100, output signal S _TemP from temperature sensor 111 exhibits corresponding changes. When the temperature, as indicated by signal S _Temp , increases such that the sampled, quantized signal S _T e _mP [n] reaches threshold value TH, logic 131 generates the signal EN so as to transition switch 120 from bypass mode to active mode (switch 120 is in position "2" so as to couple voltage V _bat of battery 110 to the input of SMPS 121). Consequently, voltage V _SM p _S from SMPS 121 is applied to the LDO 122, and LDO 122 regulates the voltage V _SM p _S to V _LDO .

[0018] In addition, even if core-circuitry 101 is in a low-power standby mode through, for example, software control, some implementations might still employ a method that generates the signal EN so as to transition switch 120 from bypass mode to active mode (switch 120 is in position "2") when the temperature increases such that the sampled, quantized signal S _Temp [n] reaches threshold value TH. Such event might occur if the system 100 is located in a relatively warm location that raises the temperature of system 100 without being in an active state.

[0019] Since total quiescent IDDQ current of system 100 comprises IDDQ leakage current of SMPS 121 and IDDQ leakage current of core-circuitry 101, the threshold temperature selected to switch from bypass to active modes might be influenced by several factors including conversion of i) current delivered at voltage node Vic _∞re to drive the ICs core circuitry 101 to ii) battery current delivered at voltage node V _bat of battery 110. Such conversion occurs with differing relative efficiency of SMPS 121 when compared to relative efficiency of LDO 122. Such conversion might be a factor since conversion by SMPS 121 is more efficient than conversion by LDO 122, yielding lower loss through heat and, consequently, less overhead current drawn at battery 110. [0020] Therefore, there is a design trade-off between the relatively high IDDQ leakage current drawn by SMPS 121 versus lower overall total IDDQ current drawn by higher efficiency of the combination of voltage regulation by SMPS 121 and LDO 122. This design trade-off occurs at the lower relative temperatures typically present near operation of system 100 during, e.g., low processing activity and/or relatively low ambient temperature of core-circuitry 101. A designer typically sets the threshold TH such that, when transitioned from bypass mode to active mode during typical operation of system 100, SMPS 121 output voltage, V _SMPS> applied to LDO 122 counters the effects of varying total IDDQ current drawn from battery 110 to within a design tolerance of a particular implementation. Beyond threshold TH, higher efficiency of voltage regulation by including SMPS 121 in combination with LDO 122 provides lower overall total IDDQ current drawn from battery 110. [0021] Reference herein to "one embodiment" or "an embodiment" means that a particular

feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term "implementation."

[0022] While the exemplary embodiments of the present invention have been described with respect to processes of circuits, including possible implementation as a single integrated circuit, a multi-chip module, a single card, or a multi-card circuit pack, the present invention is not so limited. As would be apparent to one skilled in the art, various functions of circuit elements may also be implemented as processing blocks in a software program. Such software may be employed in, for example, a digital signal processor, micro-controller, or general purpose computer. [0023] The present invention can be embodied in the form of methods and apparatuses for practicing those methods. The present invention can also be embodied in the form of program code embodied in tangible media, such as magnetic recording media, optical recording media, solid state memory, floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The present invention can also be embodied in the form of program code, for example, whether stored in a storage medium, loaded into and/or executed by a machine, or transmitted over some transmission medium or carrier, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code segments combine with the processor to provide a unique device that operates analogously to specific logic circuits. The present invention can also be embodied in the form of a bitstream or other sequence of signal values electrically or optically transmitted through a medium, stored magnetic -field variations in a magnetic recording medium, etc., generated using a method and/or an apparatus of the present invention.

[0024] Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word "about" or "approximately" preceded the value of the value or range.

[0025] It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the scope of the invention as expressed in the following claims.

[0026] The use of figure numbers and/or figure reference labels in the claims is intended to identify one or more possible embodiments of the claimed subject matter in order to facilitate the interpretation of the claims. Such use is not to be construed as necessarily limiting the scope of those

claims to the embodiments shown in the corresponding figures.

[0027] It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the present invention.

[0028] Also for purposes of this description, the terms "couple," "coupling," "coupled,"

"connect," "connecting," or "connected" refer to any manner known in the art or later developed in which energy is allowed to be transferred between two or more elements, and the interposition of one or more additional elements is contemplated, although not required. Conversely, the terms "directly coupled," "directly connected," etc., imply the absence of such additional elements.

[0029] Signals and corresponding nodes or ports may be referred to by the same name and are interchangeable for purposes here.