A 14-bit 1.0-GS/s dynamic element matching DAC with >80 dB SFDR up to the Nyquist

Abstract

A 14-bit 1.0-GS/s current-steering digital-to-analog converter (DAC) was designed in a 65-nm CMOS process. For such current-steering DACs with a high sampling rate, the code-dependent load variations and switching glitches are a main bottleneck which limits the spurious-free dynamic range (SFDR). Dynamic element matching (DEM) has been an effective solution to randomize these glitches for a higher SFDR and also to reduce the matching requirement of the current cells for an area-efficient design which also improves the SFDR with reduced parasitic capacitance. An effective method named TRI-DEMRZ is proposed in this paper, consisting of time-relaxed interleaving, DEM and return-to-zero encoding. We also apply TRI-DEMRZ in synergy with complementary switched current sources (CSCS) to design the DAC for the purpose of a small die size and enhanced SFDR performance. Post-layout simulations show >80 dB SFDR up to the Nyquist. This DAC has a mixed 1.2 V / 2.5 V power supply and an active area of 0.48 mm2.