A Diode-Based D-2D DAC Architecture with Leakage Current Compensation for Ultra-low Power Application

A new diode-based approach (called D-2D) for implementing Digital-to-Analog Converter (DAC) is presented. This approach provides a viable option for implementing DACs for ultra-low power applications. By using diodes instead of resistors, resistances in the giga-ohms range are achieved without sacrificing area, resulting in ultra-low current consumption. Since the diodes are operating in subthreshold region with extremely low subthreshold current, the issue of gate oxide tunnelling leakage becomes a significant source of error. A back-to-back diode configuration is proposed to significantly reduce the effect of this leakage current. Device stacking technique is employed to reduce the subthreshold leakage in the unit diode and in the DAC switches. Simulation results in 22nm TSMC process of an 8-bit D-2D DAC achieves $\sigma_{\mathrm{I}\mathrm{N}\mathrm{L}}/\sigma_{\mathrm{D}\mathrm{N}\mathrm{L}}$ better than 0.3LSBs with the DAC core consuming ~220pA of current for a reference of 580mV.