Wearable ASIC enables biopotentialpatient monitoring

Wearable ASIC enables biopotentialpatient monitoring

IMEC (Leuven, Belgium) has provided details on an improved version of a circuit and ASIC design for wearable biopotential monitoring systems. The complete biopotential acquisition ASIC (BASIC) takes just 160 μA and advances the state of the art on several fronts. The ASIC is primarily analog and includes an instrumentation amplifier with a fully integrated 200-Hz high-pass filter capable of rail-to-rail dc-offset rejection without compromising the CMRR (120 dB).

The design is able to do real-time motion-artifact suppression before the A/D converter, increasing system robustness when the user is moving around. The artifact removal accomplished in the analog portion of the design enables significant system power savings. The ASIC has three readout channels with each having an ECG and a complex impedance output. To accommodate electrode-tissue impedance (ETI) measurements, each channel has an AC-current source. The channel outputs (plus extra sensor inputs) are digitized by five SAR A/Ds, which can be selectively operated at 8 Ksamples/s/channel (oversampling mode) or 500 samples/s/channel. Their outputs are time-multiplexed on a master SPI output line.

The BASIC IC features configurable A/D resolution and support for accelerometers and temperature sensors.

The outputs are post processed in an MCU and fed back to the ECG channels through three D/A converter channels to accomplish motion-artifact suppression. A configurable A/D resolution and support for external sensors such as accelerometers and temperature sensors further enable the use of the BASIC for multi-modal information acquisition.

Imec and Samsung presented a paper on this topic at the recent International Solid State Circuits Conference (ISSCC) in San Francisco (SESSION 6 / Medical, Displays and Imagers / 6.5). Imec is now providing a nonexclusive license for this design.

Jim Harrison