Toshiba Corp developed a technology to reduce power consumption of a device by frequently switching its SoC to the "deep sleep" mode.
Toshiba reduced power consumption of a prototyped information terminal by 50-80% by applying the new technology to the terminal equipped with an electronic paper (e-paper) display. The company plans to further advance the research and development of the technology and provide it along with the company's SoC.
The meaning of the deep sleep defined by Toshiba is a state in which all of the circuit blocks of the CPU of an SoC and peripheral circuits stop their operations and the external clock is in the off state. Usually, an SoC is switched to the deep sleep mode only when the user suspends operation of the device or when the remaining battery level is lower than a certain level. So, when a device is being used, it normally is not switched to the deep sleep mode.
For reducing power consumption of a device being used, there has been a technology that suspends operations of the circuit blocks of a CPU and peripheral circuits depending on the situation when the external clock is in the on state.
The new technology automatically switches an SoC to the deep sleep mode by finding a chance to suspend it even when the device is in operation. It was realized by developing a technology to determine whether to switch to the deep sleep mode and improving the speed of switching to and waking up from the deep sleep. It is implemented by making changes to the program of the kernel of Linux.
This time, Toshiba tested the technology with Freescale Semiconductor Inc's "i.MX508" SoC and an e-paper display and checked the effects of the technology by using them as an Android-based information terminal. When the terminal was on but not being operated by the user, the new technology reduced power consumption from 76.22mW to 15.54mW on average. When the user was operating the terminal while viewing a document, it reduced power consumption from 114.33mW to 59.57mW on average.