The Reference Design of Portable Devices

Published:2011/8/29 1:06:00 Author:Li xiao na From:SeekIC

A low-power display/keyboard/processor/sensor reference design and demo board for handheld products will be produced by Sharp and component distributor Arrow. Called Oryx runs on 26mW and contains hardware common to many handheld devices, and advanced features like wake-on-shake.

The application code and proprietary hardware are added by the adopters, and do the production engineering. No matter whether it is portable devices in the medical or industrial sector, sport and fitness computers, point-of-sale terminals, toys or remote controls, they all have the same functions, such as a display, sensors, CPU, RTC [real-time clock], memories and input interface. The long standby time is what the owners expect most. Components come from Sharp, NXP, Analogue Devices and Linear Technology among others.

Among all the components, the display is the most special part, take sharp’s “memory LCD” as an example. It saves energy by doing away with refresh scanning. it has a bit store built into each pixel instead. The 34mm 96x96 LS013B4DN04 is the particular one, which consumers 2µA holding a static image, and 4µA when refreshed once a second. An ARM Cortex M0 variant is used as a processor.

With the clocking, NXP LPC11U14 microcontroller is the main power consumer. It requires 8 mA at 50MHz. The NXP temperature sensor ranks second, which needs 300µA max (100µA typical, 200pA stand-by), followed by the 200µA RTC.



There is a 366µA sleep mode when the screen is off and only basic CPU functions. The 2.3µA deep power down mode is followed it. To awaken from the deep sleep, the reference design includes an accelerator sensor which signals to the CPU to start operating as soon as the device is moved. This is useful for remote controls which are left lying around for long periods of time. Small solar cells that deliver 1mW from room lighting and 300mW in sunlight are also made by Sharp. It is able to charge lithium ion battery or a super capacitor in deep power-down mode; therefore, an external charger is never needed.

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