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Body-chip breakthroughs unveiled

British medical electronics pioneer Toumaz demonstrated one of the first implementations of the standard for body area networks.

BAN applications involve wireless devices worn on or close to the body, and require low power consumption coupled with security and reliability.

The Toumaz chip complies with the current draft of the 802.15.6 wireless BAN standard, which was approved in mid-2011 and should receive full IEEE ratification this year.

It also features the existing Bluetooth Low Energy 4.0 specification. Built on a 130nm process, its power consumption is no more than 14.5mW and can be as low as 1.7mW.

“Multi-mode operation offers the best solution in terms of flexibility and interoperability between devices and networks,” said Alan Wong, head of IC design.

“And the appropriate protocol can be chosen to optimise power consumption in numerous applications scenarios where data throughput varies dramatically, such as streaming multi-lead ECG or episodic temperature measurements.”

Other innovations at this year’s ISSCC included a device that can be directed through blood vessels and a highly efficient technique for filtering out the noise that affects portable or disposable monitoring patches while a patient is moving.

Stanford researchers’ guidable implant achieves something once thought impossible. The team overcame difficulties in modelling a device powered by high frequency radio waves by treating human tissue as a dielectric rather than, as has happened historically, as a good conductor.

The earlier strategy had come up against the quasi-static approximation in Maxwell’s Equations.

By adopting this approach, Stanford found that tissue does not absorb as much of a radio signal as had been thought and that even high frequency radio waves travel much further into the body than had been thought.

As a result, a small device where the waves induce enough voltage to magnetically drive the chip is possible.

Separately, to overcome the distortion created by motion artefacts (MAs) on a wearable heart monitor, researchers at IMEC and KU Leuven of Belgium and the Samsung Advanced Institute of Technology in Korea, have developed BASIC (Bio-potential Acquisition ASIC).

MA suppression has required digital post-processing, but this needs a very large dynamic range readout circuit, and results in high power dissipation due to the need for high-resolution analogue-to-digital converters.

BASIC is smaller and more power efficient because it suppresses MAs in the analogue domain.

A least mean-square filter estimates artefacts in the readout based on electrode tissue impedance.

This estimate is fed back from an off-chip microcontroller through a digital-to-analogue converter (DAC). The DAC’s output is then ‘cleaned’ from the raw ECG before final amplification by a programmable gain amplifier.

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