An enhanced ISI shaping technique for multi-bit ΔΣ DACs

This paper presents an improved ISI shaping technique for multi-bit ΔΣ DACs. Compared to the prior ISI shaping method (Lars Risbo et al, JSSC, 2011) that monitors only the up (0 → 1) transitions, the proposed technique makes use of both the up and down (1 → 0) transitions with negligible hardware cost. It provides a finer control of the transition activity, thereby improving the ISI shaping effect. In addition, due to the tight coupling between the ISI and mismatch shaping loops, the proposed technique also improves the mismatch shaping result. Simulation results show that it can reduce ISI induced distortions by 10 dB compared to the prior ISI shaping technique and 50 dB compared to DWA.