An ultra-low-power fully-differential ASK demodulator with 12.5 pJ/bit FOM for implantable biomedical applications

In this paper, we propose a fully-differential amplitude-shift-keying (ASK) demodulator for suppressing the effect of undesired common mode variations on the received data, In addition, the ASK demodulator is robust against power supply ripples. The proposed demodulator consists of a fully-differential envelope detector (ED), programmable gain amplifier (PGA) and a differential comparator. The ED and PGA operate in the sub-threshold region and the inverter based comparator consumes only dynamic current, making it highly power-efficient. The proposed system is implemented in a 0.18 µm CMOS process and consumes 2.5 µA from a 1 V power supply. At a data rate of 200 kbps, this leads to an FOM of 12.5 pJ/bit.