Programmable Current Mode Sensor Interface System for Biomedical Implantable Applications

architectures have spurred considerable interest in implantable biomedical devices. The sensor interface is one of the critical building blocks in an implantable device. The main challenge in design of biomedical sensor interfaces is the nature of physiological signals. The amplitude range of physiological signals varies between 50 - 500 μV with frequency bandwidth from 0.1 Hz to 500 Hz. Therefore, low noise design is the major concern in developing of biomedical sensor interfaces. Objective: To design a low-voltage low-power high-performance biomedical sensor interface. Results: The input signal range is 0-5mV and the acceptable signal frequency range is from 0.1Hz to 500Hz. The resolution of the current mode successive approximation analog to digital converter is 8 bit. The circuit is simulated in 0.18μm CMOS technology with supply voltage of 1.8 V. At 40 Ks/S sampling frequency, the total power consumption and total harmonic distortion of the system are obtained 2.2 μW and -45.2 dB respectively. Conclusion: A low power current mode circuit is presented for biomedical sensor interface applications. An adaptable band- pass filter is used in front end of the system for providing flexibility in its passband for different biomedical applications. The Gm and current mode SAR ADC are designed in a way to achieve minimum power consumption. The simulation results demonstrated the effectiveness and superiority of the proposed circuit in comparison with the conventional circuits.

Biomedical Instrument Sensor Interface Current Mode Analog To Digital Converter 0.18μm Cmos Technology