TECH UPDATE EXCLUSIVE
Reducing Power Consumption Enhances Device Functionality
The PIC10F family of 8-bit MCUs from Microchip Technologies Inc. features control peripherals that can be used to manipulate power consumption.
Companies such as Microchip Technologies Inc. (Chandler, AZ) that specialize in semiconductors and electronic components are developing features in MCUs to improve power consumption rates at the manufacturing level. "We're using old techniques more creatively," says Steve Kennelly, manager, medical products group, Microchip. "We're optimizing the chemistry of the wafer in the semiconductor and designing chips to minimize power consumption."
Managing power consumption begins with a device designer's power budget. A power budget is developed as part of the initial design of a device to determine or anticipate the sizes and power requirements of the device components and the device as a whole. "[It should be] evaluated at the beginning and at each step of the design process," Kennelly says. "Setting the criteria of a power budget is critical, especially for devices where it is not easy to change batteries or where longevity of battery life is key, such as in pacemakers."
To further reduce power consumption, companies are developing technologies that enable the cpu in the microcontroller to take on-chip peripherals off of the chip from a power budget standpoint by stopping them from drawing any current
One key area where semiconductor designers are cutting power consumption is leakage current, the power used by electronic components when they are not actively operating. "The key is to power up quickly," says Todd Schneider, vice president, diagnostics, therapy, and monitoring, medical business unit at AMI Semiconductors (Pocadello , ID). "The faster you can wake the chip up, operate it while it is awake, and put it back to sleep, the longer it can stay in sleep mode."
Sleep-mode features can be used to periodically switch certain functions on and off when they are needed. According to Schneider, the sleep-mode features use radio-frequency technology to periodically--every second for example--wake up, check for a transmission to see if a function needs to be performed (a process that takes a few hundredths of a second), and go back to sleep. Cycling portions of a semiconductor to turn off when it's not being used, says Schneider, is one way to help minimize leakage current.
Several other semiconductor features can be used to manipulate power consumption, but both Kennelly and Schneider emphasize using as many methods as is appropriate for the application. "Implantable devices have very strict power budgets so they typically use all methods," says Schneider. "Portable devices that have looser power constraints may only use some methods."
Schneider also notes a trend toward incorporating wireless components into medical devices such as hearing aids. For example, AMI manufactures a chip called Ezairo for hearing aids that uses a 130-nm process designed to deliver twice the computing power of previous digital signal processor systems at a lower rate of power consumption. Wireless components increase power usage in devices, therefore, manufacturers are going to need to rely more on multichip systems to push the fundamental limitations of device size and power usage, according to Schneider. "Three to four years ago, there were almost no [wireless components used in hearing aids]. But it's going to be a force in the future for sure," he says.