Design and implementation of a FPGA sigma-delta power DAC

In this paper we discuss the design and implementation of a FPGA power DAC for digital audio applications. The paper concentrates on the sigma-delta modulator, which is used to convert an oversampled PCM input signal into a 1-bit code suitable for controlling a power switch. The design of the bit-flipping architecture used to reduce the pulse-repetition frequency of the output is discussed, together with the the loop filter structure and transfer function design. This is followed by details of FPGA architecture and the optimisations required for implementation.