Energy efficient silicon chip
Researchers from MIT in Boston and Texas Instruments (TI) in Dallas, both in the USA, have designed a silicon chip with a DC/DC converter built directly on it, making it up to 10 times more energy efficient than other versions. This could provide longer lasting portable battery-operated devices.
The silicon chip, which was demonstrated on TI’s MSP430 microcontroller, operates at 0.3V (most chips operate at one volt). This was achieved by building the DC/DC converter right onto the chip, allowing voltage to be programmed by a switching matrix and capacitor.
‘DC/DC converters have been built on chips before. However, this is the first effort to make it on-chip for low voltages with high efficiency. Several new ideas have been integrated,’ says Professor Anantha Chandrakasan of MIT Microsystems Technology Laboratories. These include varying grain settings for different voltage levels to minimise conduction losses, and employing charge recycling to improve efficiency.
To minimise the chip’s vulnerability to variations caused by lower voltages, the team also redesigned static random access memory (SRAM) circuits using new circuit topologies. ‘One problem in SRAM is that when you read a memory using conventional architecture, you can flip the state of the memory,’ says Chandrakasan. ‘To address this we used a “buffered read” which does not disturb the state during the read.’
Terence O’Donnell, Senior Research Officer at the Tyndall Institude in Cork, Ireland, calls the design ‘a major step forward’, but cautions that on-chip switching converters need passive components to be integrated, ‘which is a technology that still requires considerable development’.
Researchers are working on further aspects of the low-power design, including analog-to-digital converters. They believe a commercial application could be ready within five years.