A 0.5-V 250-nW 65-dB SNDR passive ΔΣ modulator for medical implant devices

A 0.5-V ultra-low-power second-order DT ΔΣ modulator is presented in this paper for medical implant devices. The modulator employs 2^nd-order passive low-pass filter and ultra-low-voltage building blocks, including preamplifier, regenerative comparator, and clock controller, in order to enable operation near 0.5 V supply. A low-noise and gain-enhanced single-stage preamplifier is developed using a body-driven technique. Passive filter is gain boosted by power-efficient charge-redistribution amplification scheme. Designed in a 65nm CMOS technology, the modulator achieves 65 dB peak SNDR over a 500 Hz signal bandwidth, while it consumes 250 nW from a 0.5 V supply. The modulator is functional at 0.45V and obtains 52 dB SNR, while consuming 200 nW.