A 12.5-Gbps, 7-bit transmit DAC with 4-tap LUT-based equalization in 0.13μm CMOS

This paper presents a 12.5-Gbps transmitter that uses a lookup table (LUT)-based equalizer to compensate for within-die imperfections. An equalization technique with 2x sampling is proposed to accommodate timing offsets in the multiphase clocks used for 8:1 serialization. LUT code remapping is also demonstrated to compensate for mismatch effects that introduce nonlinearity in the transmit DAC. Experimental results of a 7-bit resolution transmitter with 4-tap equalization, implemented in 0.13 mum CMOS, show the LUT-based equalizer can significantly improve the signal integrity of an otherwise closed eye for data transmitted at 12.5-Gbps.