A Low-Power 0.7 μ Vᵣₘₛ 32-Channel Mixed-Signal Circuit for ECoG Recordings

Monitoring of electrocorticography signals using multi-electrode array creates new opportunities for neural prosthetic applications. In this paper, we present a 32-channel recording ASIC that provides low-noise amplification and analog filtering. It also includes a 12-bit analog-to-digital conversion function, and offers programmable output rates through a serial peripheralinterface (SPI). The targeted application is a remote-powered wireless implantable ECoG recording system. Each recording channel has a measured 0.7 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">μ Vᵣₘₛ</tex></formula> input-referred noise on a [0.5–300 Hz] bandwidth. The device was fabricated in a 0.35 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">μ m</tex></formula> complementary metal–oxide–semiconductor process for a total die area of 86 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">mm ²</tex></formula> with an analog power consumption limited to 134 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">μ W</tex></formula> per channel.