An all-digital low-power, low-frequency GRO-based time to digital converter for biomedical applications

In this paper, an all-digital, 10-bit, low-power Time-to-Digital Converter (TDC) is proposed for use in biomedical applications. To reduce the area and power consumption, as well as provide noise shaping capability, the Gated Ring Oscillator (GRO) architecture is chosen as the core for the proposed TDC. Regarding the problems created by the leakage current in GROs, especially in low-frequency applications, a new approach for data capturing is used. The proposed modified data capturing method tackles the leakage current effect and allows the TDC to operate at ultralow frequencies. The proposed TDC achieves a dynamic range of 1.76 µs, and the resolution of 1.76 ns at 1KS/s sampling frequency. Simulations were performed using the 0.13 µm CMOS process. The TDC power consumption was 45.85 nW at a 0.4 V supply and the Signal to Noise and Distortion Ratio (SNDR) was 54.55 dB.