Sub-Threshold ARM Chip on Track at Ambiq

Peter Clarke
9/19/2013 11:22 AM EDT
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​Fabless startup Ambiq Micro Inc. is on track to start sampling an ARM-based microcontroller that operates transistors near and below their threshold voltage in 2014. Volume production of sub-threshold microcontrollers is then expected in 2015, Scott Hanson, chief technology officer of Ambiq, told EE Times in a telephone interview.

Ambiq, based in Austin, Texas, has also announced it has raised $10 million in a Series B funding round led by Austin Ventures and with participation of the company’s existing shareholders, including ARM Holdings plc, which will help fund the development of MCU chips and expand the company’s market presence.

Hanson said Ambiq is designing mixed-signal devices based on the Cortex-M0+ core from ARM, but rather than being general-purpose MCUs, these MCUs are tailored for emerging applications where power consumption is critical. Typical applications would include: wearable devices, smartcards, wireless sensors, and portable medical equipment, he told us.

While sub-threshold operation limits the attainable clock frequency and performance of digital circuits when compared to conventional operation, the technique reduces significantly the power consumption of such circuits.

On its website, Ambiq describes its sub-threshold power-optimized technology (SPOT) process as turning “microamps into nanoamps.” The threshold where a transistor can be turned on and significant current flows is in the region of 0.3 to 0.6V, depending on the manufacturing process, but around the threshold, the device characteristics have exponential dependencies on voltages and temperature making design difficult.

Ambiq was formed in 2010 — with backing from ARM Holdings plc among others — to commercialize sub-threshold research carried out at the University of Michigan. However, the company’s first products were the AM08XX and AM18XX real-time clock (RTC) chips, which the company claimed were the world’s lowest power RTC chips due to their use of the SPOT process. (See: Ambiq launches nanoampere RTC chips.)
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“They are seven times more power efficient than the nearest competitors and producing attractive revenue right now. They are a big driver to getting us cash-flow positive in the very near future,” Hanson said.