Design of a fully-digital class-D audio power amplifier based on open-loop configuration

A fully-digital open-loop class-D audio power amplifier is presented. By using the proposed error feedback structure, the ΔΣ noise shaper reduces the word length of the input signal while maintaining its precision. An optimized compensation algorithm based on 2x interpolation linearization is proposed to improve the total harmonic distortion (THD), as well as to reduce its hardware overhead. The whole system has been implemented in the standard SMIC 0.18µm 1P6M Logic Salicide process. The test results show that the system achieves a maximal SNDR of 82.9dB and a dynamic range of 83.7dB with a power consumption of 0.12mW under a supply voltage of 1.8V, which is suitable for the application of high-fidelity audio systems.