This paper describes the design methodology and calibration technique for a low-power digital pulse width modulation demodulator to enhance its robustness against the process, voltage, and temperature variations in different process corners, in addition to intra-die variability, which makes it a very good choice for implantable monitoring sensors. Furthermore, the core of the proposed demodulator is fully digital. Thus, along with the proposed design methodology, the proposed demodulator can be simply redesigned in advanced subnanometer CMOS technologies without much difficulty as compared to analog demodulators. The proposed demodulator consists of an envelope detector, a digitizer, a ring oscillator, and a data detector with digital calibration. All the proposed circuits are designed and simulated in the standard 1P9M TSMC’s 40 nm CMOS technology. Simulation results have shown that the circuit is capable of demodulating and recovering data from an input signal with a carrier frequency of 13.56 MHz and a data rate of 143 kB/s with an average power consumption of 5.62 μW.
The Design Methodology of Fully Digital Pulse Width Modulation