A compact dynamic-performance-improved current-steering DAC with random rotation-based binary-weighted selection

Conventional binary-weighted current-steering DACs are generally operated with current groups where each group is binary-weighted and formed with predetermined members of a unit current-source array. This paper proposes a random rotation-based binary-weighted selection (RRBS) that efficiently performs dynamic-element matching (DEM) by randomly rotating the sequence of these units to form new binary-weighted current groups for each DAC output. Without using binary-to-thermometer decoders, RRBS features its simplicity and compactness of DEM realization. Compared to conventional binary-weighted DACs, RRBS DACs are insensitive to the mismatch of small-size current-sources and exhibit better dynamic performance. A 10-bit RRBS DAC is implemented with only 0.034 mm ² in a standard 1P6M 1.8 V 0.18 μm CMOS process. Measured performance achieves >61 dB spurious-free dynamic range (SFDR) in the Nyquist bandwidth with 500 MS/s, while its active area is less than one-tenth of that required by state-of-the-art 10-bit current steering DACs. To the best of our knowledge, the proposed RRBS implements the smallest area for high-speed current-steering DACs up to now. Its SFDR is also comparable to that of 12-bit published designs. Three popular figures-of-merit (FOMs) are used to compare this design with other state-of-the-art 10-12-bit DACs, with the proposed design performing best with 2 FOMs.