4xVDD ASK demodulator using standard 3.3 V CMOS device for implantable biomedical micro-stimulator

This paper proposes a 4xVDD ASK demodulator using standard 3.3 V device in 0.35 μm CMOS process for the implantable biomedical micro-stimulator. Traditional implantable biomedical ASK demodulator receives the ASK modulated signal with the maximum voltage of 6 V such that it needs a step-down circuit in the system. On the other hand, in order to drive the high-impedance nerve and micro-electrode, a DC-DC converter and the HV process are required to boost the voltage to be larger than 10 V. By using the rectifier with cascoded diode-connected NMOS transistors, the proposed 4xVDD ASK demodulator can receive the ASK modulated signal with the maximum voltage of 14 V. Thus, it discards the step-down circuit, the boost circuit and HV process in the system. The maximum data rate is simulated to be 1.25 Mbps with the carrier frequency of 12.5 MHz. The core area is 109.515 × 56.925 μm².