A 1.8-μW sigma-delta modulator for 8-bit digitization of cardiac signals in implantable pacemakers operating down to 1.8 V

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.