Current mode sensor interface system for biomedical implantable applications

In this paper we present a low power interface circuit with the new approach of current mode successive approximation (SAR) ADC for biomedical implantable devices application. The circuit includes band pass filter, Gm and current mode SAR ADC. The SAR ADC is a low power circuit that is composed of current mode S/H, current mode comparator, current mode DAC and conventional logic. In this circuit the signal input range is between 0-5mV and the acceptable signal frequency range is from 0.1Hz to 500Hz. The resolution of the current mode SAR ADC is 8 bit with the LSB of 500pA. The circuit is simulated in a 0.18μm CMOS technology using supply voltage of 1.8V. At the sampling frequency of 40Ks/S the total power consumption is 2.2μW.