Mobile Gaming: The Next Power-Saving Frontier

By Pallab Chatterjee
Mobile and handheld gaming platforms are gaining lots of attention these days, and from a low-power engineering standpoint it poses a challenge that dwarfs any game played on the devices.

Unlike mobile phones, these handheld platforms don’t have the luxury of trading off between multiple operating modes to extend battery life. Even worse, they have to perform at the highest level of performance for the entire use cycle, while also supporting game sensors and actuators. Consider the new Nintendo 3DS, for example. It features dual daylight-readable auto-stereoscopic 3D displays. The system supports the same button interface as the standard DS, but pays a penalty for the displays.

The initial Nintendo DS, which featured a single screen system, operated for five to seven hours of gaming based on backlight levels. Compare that to the DSi, introduced in 2009, which ended up reducing the operating time to three to four hours. This reduction was not primarily due to the power for the second LED backlit display, but for the graphics processing needed to support the second display. For the 3DS, the performance of the core chipset and the graphics processing was once again increased. The advances in design partitioning, retiming of the input controls and better leakage power management, allow the new handheld, even with the compute complexity of the S3D display, to still provide three to four hours of battery life.

The Sony PSP and its companion product the PSP Lite are also in the long-play handheld arena. The larger battery PSP sports an eight-hour playback life in movie mode, and a six-hour operating life in gaming mode. The smaller PSP Lite targets six-hour and four-hour operation, respectively. The two models use similar graphic and processor cores, but sport slightly different displays and batteries. The main difference in operating performance is the battery.

In the handheld gaming market the target usable life between charges is four hours, and then the unit is in off mode. Most mobile handsets (smart phones, etc.), never utilize “off” as a design state. Instead they have multiple on states, including full power display + RF, text-only display + RF, audio playback (MP3), streaming video support (codecs + RF), camera mode, video-camera mode, and gaming mode. In these phone-based designs, the user interface is through the low-power touch screen and internal gyros. On the gaming handhelds, there is additional tactile feedback to the button controls, and socket-based interfaces (games, media input, display output) that operate at high sensitivity.

These same power specifications have been passed on from the gaming units to peripherals for the consoles. The highest-use wireless peripherals are the Wii controllers. They are targeted at six to seven hours of use on rechargeable battery kits, or more than 40 hours on a set of AA batteries. The replacement controllers and other components to the system – musical instrument controllers, the balance board, etc., must also have this long off-mode storage time and then full-power operations cycle. This has led to the use of a new series of high efficiency DC-DC converters from National Semi and Linear Technology. With the availability of these parts, the Xbox and PS3 wired controllers have started to be replaced by high-performance wireless versions from third parties.

The new wireless controllers, have modern MEMS based position controls, high data rate RF interfaces, and general LED lighting options. The controllers are targeted for 10-plus hours on a charge from built-in batteries. The majority of these controllers have their functionality in FPGAs or small platform ASICs, and utilize linear standard parts for sensor control and power management. This partitioning allows them to address both the price point and the power cycle requirements.