A 94dB-SNR −76dB-THD high-efficiency hybrid audio power-DAC for loudspeaker (4Ω/8Ω) and earphone (16Ω/32Ω)

This paper presents a high-efficiency audio DAC with a class-AB power output stage in the analog reconstruction filter. This closed-loop solution reduces power stage noise and linearity specs, reduces the active device number, and, definitively, reduces power consumption, increasing efficiency. Moreover, a novel control system allows, at the same time, to reduce output offset and idle tone generated by the digital structure. In a 0.15μm CMOS technology at 2.7V supply, the powerDAC performs 94dB-SNR, and -76dB-THD on 80-load. The output offset is reduced to be lower than 500μV. The efficiency FoM defined as DeliveredPower/QuiescentPower of the overall analog block is >40 (on a 16 load), while the efficiency FoM of the earphone PA stand alone is 56. In both case the proposed device efficiency outperforms the state-of-the-art [6-9].