WO2009035254A2

WO2009035254A2 - Apparatus and method for reducing power consumption in system on chip

Info

Publication number: WO2009035254A2
Application number: PCT/KR2008/005325
Authority: WO
Inventors: Sung-Min Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2007-09-11
Filing date: 2008-09-10
Publication date: 2009-03-19
Anticipated expiration: 2010-03-11
Also published as: WO2009035254A3; CN101802750A; CN101802750B; KR101429674B1; EP2188693A4; US20100205468A1; KR20090026895A; US8667313B2; EP2188693B1; EP2188693A2

Abstract

An apparatus and method for reducing power consumption in a System on Chip (SoC) are provided. The SoC includes a clock unit for providing clocks to all elements included in the SoC, a Central Processing Unit (CPU) for controlling the SoC to perform designated functions, a main regulator for supplying power provided from an external battery to remaining elements included in the SoC other than a PMU, and a restoration processor for storing, in the PMU, registration information on the CPU and all peripherals included in the SoC when a transition from an active state to a sleep state is made. The PMU stops provision of a clock from the CPU by controlling the clock unit for stopping provision of all clocks by controlling the clock unit and for controlling the main regulator to be powered off when the restoration processor, wherein the PMU requests the restoration processor to store the registration information, completes the register information storing, when the transition from the sleep state to the active state is made.

Description

APPARATUS AND METHOD FOR REDUCING POWER CONSUMPTION IN SYSTEM ON CHIP

Technical Field

[1] The present invention relates to an apparatus and method for reducing power consumption in a System on Chip (SoC). More particularly, the present invention relates to an apparatus and method for reducing power consumption by performing an operation of an SoC in such a manner that last operation information of all elements included in the SoC is stored when the SoC is powered off and the stored last operation information is restored when the SoC is powered on. Background Art

[2] In general, a System on Chip (SoC) used in communication systems controls power by using several methods for reducing power consumption. When the SoC is used in a Wireless Personal Area Network (WPAN), the SoC operates in an active state for a short period of time and operates in a sleep state for most periods of time to minimize power consumption.

[3] A control method for reducing power consumption of the SoC may be implemented in a software manner. However, an operation of a Central Processing Unit (CPU) and the use of program memories may increase power consumption. Therefore, in general, it is more effective to implement the control method in a hardware manner.

[4] There are three representative conventional methods for reducing power consumption in a hardware manner. In a first method, in order to reduce power consumption, an internal clock is off when power is off. In this method, the clock provided to all elements of the SoC can be controlled for each element by determining an active state of the SoC. Further, in this method, power consumed by a dynamic current can be reduced by turning off the clock, while power consumed by a leakage current cannot be reduced. In a WPAN-type SoC, a sleep state occupies more than 80% of chip operations, and thus the leakage current is more important than the dynamic current. Accordingly, the first method cannot ultimately solve the power consumption problem.

[5] In a second method, a special register called a retention register is used. The retention register can store a present state by using data retention power when operation power is off. The retention register has an element capable of storing data by consuming a minimum leakage current by the use of retention power. However, the retention register is almost two times larger in size than a general register. In addition, since the retention register is not in a full power-off state, the leakage current leads to power consumption. [6] In a third method, a previous state, which is immediately before power is off, is restored through initialization in which register information of the CPU and peripherals included in the SoC is lost and then the SoC is entirely reset when power is on by performing an actual power-off.

[7] Among the aforementioned three methods, the third method is a best method in terms of reducing power consumption. However, when power is on, it takes time to restore the previous state, which is immediately before the power is off, through reset and initialization, and during the time, power is consumed due to an operation of the SoC. Disclosure of Invention Technical Problem

[8] An aspect of the present invention is to solve at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and method for reducing power consumption in a System on Chip (SoC).

[9] Another aspect of the present invention is to provide an apparatus and method for reducing power consumption by operating only an auxiliary regulator that detects a transition from a sleep state to an active state in a SoC.

[10] Another aspect of the present invention is to provide an apparatus and method for reducing power consumption by performing an operation of an SoC in such a manner that last operation information of all elements included in the SoC is stored when the SoC is powered off and the stored last operation information is restored when the SoC is powered on.

[11] In accordance with an aspect of the present invention, an SoC for reducing power consumption is provided. The SoC includes a clock unit for providing clocks to all elements included in the SoC, a Central Processing Unit (CPU) for controlling the SoC to perform designated functions, a main regulator for supplying power provided from an external battery to remaining elements included in the SoC other than a Power Management Unit (PMU), a restoration processor for storing, in the PMU, registration information on the CPU and all peripherals included in the SoC when a transition from an active state to a sleep state is made. The PMU for stopping provision of a clock from the CPU by controlling the clock unit, for stopping provision of all clocks by controlling the clock unit and for controlling the main regulator to be powered off when the restoration processor, wherein the PMU requests the restoration processor to store the registration information, completes the register information storing, when the transition from the sleep state to the active state is made.

[12] In accordance with another aspect of the present invention, a method of reducing power consumption in an SoC is provided. The method includes stopping generation of a clock to be provided to a CPU by detecting a transition from an active state to a sleep state in a PMU, storing register information of the CPU and peripherals included in the SoC, stopping provision of all clocks of the SoC, and powering off a main regulator. Brief Description of the Drawings

[13] The above and other aspects, features and advantages of certain exemplary embodiments of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[14] FIG. 1 illustrates a structure of a System on Chip (SoC) according to an exemplary embodiment of the present invention;

[15] FIG. 2 is a flowchart illustrating a process in which an SoC is initialized by tran- sitioning from a battery-off state to a battery-on state according to an embodiment of the present invention;

[16] FIG. 3 is a flowchart illustrating a process in which an SoC is powered off in an active state and then transitions to a sleep state according to an exemplary embodiment of the present invention; and

[17] FIG. 4 is a flowchart illustrating a process in which an SoC is powered on in a sleep state and then transitions to an active state according to an exemplary embodiment of the present invention. Best Mode for Carrying Out the Invention

[18] Exemplary embodiments of the invention will be described below with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

[19] The present invention relates to an apparatus and method for reducing power consumption by performing an operation of a System on Chip (SoC) in such a manner that last operation information of all elements included in the SoC is stored using an auxiliary regulator that consumes a small amount of power when the SoC is powered off in a sleep state, and the stored last operation information is restored when the SoC is powered on. Hereinafter, a structure of the SoC will be described with reference to FIG. 1.

[20] FIG. 1 illustrates a structure of an SoC according to an exemplary embodiment of the present invention. Referring to FIG. 1, an SoC 110 includes a clock unit 112, a Central Processing Unit (CPU) 114, peripherals 116, a modem 118, a Power Management Unit (PMU) 120, a restoration processor 130, and a main regulator 140.

[21] The clock unit 112 provides clocks to the CPU 114, the peripherals 116, the modem

118, the PMU 120, and the restoration processor 130 under the control of the PMU 120. [22] The CPU 114 controls the SoC 110 to provide designated functions of the SoC 110, and has a register for storing information generated when the designated functions are performed.

[23] The peripherals 116 and the modem 118 are included according to the designated functions of the SoC 110. The functions of the peripherals 116 and the modem 118 may vary depending on functional implementations. The peripherals 116 and the modem 118 also have registers for storing information generated when the designated functions are performed.

[24] The main regulator 140 rectifies an unregulated high voltage of an external batter

102 so that the high voltage is fit to the operation of the SoC 110, thereby supplying a constant voltage. The main regulator 140 receives from the PMU 120 a control signal for determining whether power is supplied. The main regulator 140 supplies the power to all elements of the SoC 110 other than the PMU 120.

[25] The PMU 120 controls the main regulator 140 to reduce consumption of power supplied to the SoC 110. The PMU 120 includes a memory 122, a controller 124, and an auxiliary regulator 126.

[26] When power is off and thus a transition to a sleep state is made under the control of the restoration processor 130, the memory 122 stores last states of respective registers of the CPU 114, the peripherals 116, and the modem 118. When power is on and thus a transition to an active state is made, the memory 122 provides the stored last states of the respective registers of the CPU 114, the peripherals 116, and the modem 118 to the restoration processor 130.

[27] The auxiliary regulator 126 supplies a constant voltage power to the PMU 120. The auxiliary regulator 126 has a lower operation current and power consumption than the main regulator 140. Once power is supplied from the battery 102 after booting, the auxiliary regulator 126 continuously operates in the sleep state or the active state.

[28] The controller 124 detects the transition to the sleep state or the active state. When the transition to the sleep state is made, the controller 124 controls the clock unit 112 to stop generation of the clock to be provided to the CPU 114, and transmits a storage request message (i.e., store_start) to start storing of the last states of the various registers. Upon receiving a storage completion message (i.e., store_end) from the restoration processor 130 to indicate that the last states of the various registers are completely stored, the controller 124 controls the clock unit 112 to stop generation of the clocks to be provided to remaining elements other than the CPU 114, and transmits a power-off signal to the main regulator 140.

[29] When the transition from the sleep state to the active state is detected, the controller

124 transmits a power-on signal to the main regulator 140, and controls the clock unit 112 to generate the clocks to be provided to the remaining elements other than the CPU 114. Further, the controller 124 transmits a restoration request message (i.e., restore_start) to the restoration processor 130 to start restoration of the last states of the various registers by using stored information. Upon receiving from the restoration processor 130 a restoration completion message (i.e., restore_end) for informing that the last states of the various registers are completely restored, the controller 124 controls the clock unit 112 to generate the clock to be provided to the CPU 114, so that the SoC 110 normally operates in the active state to perform the designated functions.

[30] The controller 124 determines that the transition from the sleep state to the active state is detected when a reset signal or an interrupt signal is received from an external element or when generation of a wake-up signal is detected according to an operation of a sleep timer.

[31] Upon receiving the store request message (i.e., store_start) from the controller 124, the restoration processor 130 stores in the memory 122 the last states of the respective registers of the CPU 114, the peripherals 116, and the modem 118. When the storing of the last states is finished, the restoration processor 130 generates the storage completion message (i.e., store_end) and transmits the generated message to the controller 124.

[32] Further, upon receiving the restoration request message (i.e., restore_start) from the controller 124, the restoration processor 130 restores the respective registers' last states stored in the memory 122. When the restoration of the last states is finished, the restoration processor 130 generates the restoration completion message (i.e., restore_end) and transmits the generated message to the controller 124.

[33] Now, a method of reducing power consumption in an SoC with the aforementioned structure according to exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In this method, a last state is stored when the SoC is powered off and is restored using stored information when the SoC is powered on.

[34] FIG. 2 is a flowchart illustrating a process in which an SoC is initialized by tran- sitioning from a battery-off state to a battery-on state according to an embodiment of the present invention. Referring to FIG. 2, in step 200, the SoC detects a transition from the battery-off state to the battery-on state. The battery-off state is a state in which power cannot be supplied from a battery. The battery-on state is a state at which power starts to be supplied from the battery. In step 202, an auxiliary regulator is powered on. In step 204, when a regulated voltage is supplied from the auxiliary regulator, a PMU for managing the SoC operates. In step 206, under the control of the PMU, a main regulator is powered on. In step 208, when a regulated voltage is supplied from the main regulator, clocks are generated and provided to all elements included in the SoC. In step 210, designated functions of the SoC are performed by operating the SoC in an active state in which the SoC is powered on.

[35] FIG. 3 is a flowchart illustrating a process in which an SoC is powered off in an active state and then transitions to a sleep state according to an exemplary embodiment of the present invention. Referring to FIG. 3, while operating in the active state in step 300, if the SoC detects occurrence of a condition for transitioning to the sleep mode in step 302, generation of a clock to be provided to a CPU is stopped in step 304. Then, in step 306, last states of respective registers of peripherals and the CPU are stored. In step 308, generation of all clocks of the SoC is stopped. In step 310, a main regulator is powered off, and a transition is made to the sleep mode.

[36] FIG. 4 is a flowchart illustrating a process in which an SoC is powered on in a sleep state and then transitions to an active state according to an exemplary embodiment of the present invention. Referring to FIG. 4, while operating in the sleep state in step 400, the SoC detects occurrence of a condition for transitioning to the active state in step 402. The condition for detecting transitioning from the sleep state to the active state in step 402 may be receiving of a reset signal or an interrupt signal from an external element or generating of a wake-up signal according to an operation of a sleep timer.

[37] If the condition for transitioning to the active state is detected in step 402, proceeding to step 404, a main regulator is powered on. In step 406, clocks are provided to all elements included in the SoC other than a CPU. In step 408, last states of registers of the respective elements included in the SoC are restored using stored information. In step 410, a clock is provided to the CPU. In step 412, designated functions of the SoC are performed in the active state. The reason of not providing the clock to the CPU in step 406 is that, if the CPU operates before the last state is restored, the CPU starts an initial operation on a program. That is, according to the present invention, the clock is provided to the CPU after all elements are completely restored, so that the CPU starts its operation starting from a program address of an operation previously performed before power is off.

[38] According to exemplary embodiments of the present invention, an SoC includes a clock unit for providing clocks to all elements included in the SoC, a CPU for controlling the SoC to perform designated functions, a main regulator for supplying power provided from an external battery to remaining elements included in the SoC other than a PMU, and a restoration processor for storing, in the PMU, registration information on the CPU and all peripherals included in the SoC when a transition from an active state to a sleep state is made. The PMU stops provision of a clock from the CPU by controlling the clock unit for stopping provision of all clocks by controlling the clock unit and for controlling the main regulator to be powered off when the restoration processor, wherein the PMU requests the restoration processor to store the registration information, completes the register information storing, when the transition from the sleep state to the active state is made.

[39] While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents. Therefore, the scope of the invention is defined not by the detailed description of the invention but by the appended claims and their equivalents, and all differences within the scope will be construed as being included in the present invention.

Claims

[1] A System on Chip (SoC) for reducing power consumption, comprising: a clock unit for providing clocks to all elements included in the SoC; a Central Processing Unit (CPU) for controlling the SoC to perform designated functions; a main regulator for supplying power provided from an external battery to remaining elements included in the SoC other than a Power Management Unit (PMU); a restoration processor for storing, in the PMU, registration information on the CPU and all peripherals included in the SoC when a transition from an active state to a sleep state is made; and the PMU for stopping provision of a clock from the CPU by controlling the clock unit, for stopping provision of all clocks by controlling the clock unit and for controlling the main regulator to be powered off when the restoration processor, wherein the PMU requests the restoration processor to store the registration information, completes the register information storing, when the transition from the sleep state to the active state is made.

[2] The SoC of claim 1, wherein the restoration processor reads the register information stored in the PMU when a transition from the sleep state to the active state is made, and restores all registers of the CPU and the peripherals included in the SoC, and wherein, when the transition from the sleep state to the active state is made, the PMU controls the main regulator to be powered on, controls the clock unit to provide clocks to units included in the SoC other than the CPU, and controls the clock unit to provide the clock to the CPU when the restoration, wherein the PMU requests the restoration processor to restore the register information, is completed.

[3] The SoC of claim 1, wherein the PMU comprises an auxiliary regulator for supplying the PMU with power provided from the external battery.

[4] The SoC of claim 3, wherein the auxiliary regulator supplies power to the PMU in the active state and the sleep state.

[5] The SoC of claim 3, wherein the auxiliary regulator has a lower operation current and power consumption than the main regulator.

[6] A method of reducing power consumption in an SoC, the method comprising: stopping generation of a clock to be provided to a CPU by detecting a transition from an active state to a sleep state in a PMU; storing register information of the CPU and peripherals included in the SoC; stopping provision of all clocks of the SoC; and powering off a main regulator. [7] The method of claim 6, further comprising: upon detecting a transition from the sleep state to the active state in the PMU, powering on the main regulator; providing clocks to elements included in the SoC other than the CPU; restoring the stored register information; and providing the clock to the CPU. [8] The method of claim 6, further comprising: powering on an auxiliary regulator of the power manger when a battery is powered on in a battery-off state; powering on the main regulator under the control of the PMU; and providing clocks to all elements included in the SoC. [9] The method of claim 6, wherein the PMU comprises an auxiliary regulator for supplying power, which is provided from the external battery, to the PMU. [10] The method of claim 9, wherein the auxiliary regulator supplies power to the

PMU in an active state and a sleep state. [11] The method of claim 9, wherein the auxiliary regulator has a lower operation current and power consumption than the main regulator.