Variable input range continuous-time switched current δΣ analog digital converter for RFID CMOS biosensor applications

Continuous-time delta-sigma (ΔΣ) analog digital converter (ADC) for radio frequency identification (RFID) complementary metal oxide semiconductor (CMOS) biosensor has been reported. This ΔΣ ADC is suitable for digital conversion of biosensor signal because of small process variation, and variable input range. As the input range of continuous-time switched current ΔΣ ADC (Dynamic range: 50 dB [1], [2] can be limited by using current reference, amplification of biosensor signal is unnecessary. The input range is switched to wide input range mode or narrow input range mode by command of current reference. When the narrow input range mode, the input range becomes ± 0.8 V. The measured power consumption is 5 mW and chip area is 0.31 mm2 using 1.2 μm standard CMOS process. Additionally, automatic input range detecting system is proposed because of RFID biosensor applications.