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.