A 90dB DR audio delta-sigma DAC with headphone driver for hearing aid

This paper presents the design and implementation of a single chip audio delta-sigma (ΔΣ) DAC with headphone driver for hearing aid. It consists of a digital interpolation filter, a ΔΣ modulator, a digital low-pass filter (DLPF) encoder and a class D output stage. A structure of chain of integrators with feedforward summation and local resonator feedbacks is adopted for ΔΣ modulator to shape quantization noise. Differing from the basic structure of ΔΣ DAC, a class D output stage playing the role of headphone driver instead of the internal D/A converter is adopted. It is implemented in a 0.18 μm standard CMOS process, the die area is 2.46 mm². The ΔΣ DAC with headphone driver achieves 85.6 dB peak SNDR and 90 dB dynamic range (DR) and it consumes 4.3 mW with a 376 Ω hearing aid headphone load.