A 1.8uW Sigma-Delta Modulator for 8-bit Digitization of Cardiac Signals in Implantable Pacemakers Operating Down to 1.8V

Implantable biomedical devices can highly benefit from submicrometer CMOS technologies both in terms of duration-time increase and size shrinking. This work shows how design techniques for submicrometer CMOS technologies lead to improvements in the sensing stage of a cardiac implantable pacemaker. A sigma-delta modulator is presented for 8-bit quantization of the natural electrical activity of the heart, fabricated in a 0.8-μm CMOS technology. The low-voltage, low-power design procedure employs switched-opamp and weak inversion CMOS circuits. Measurement results confirm a power dissipation of 1.8 μW, a minimum supply voltage of 1.8 V, and more than 50 dB of dynamic range.