A 16Gb 27Gb/s/pin T-coil based GDDR6 DRAM with Merged-MUX TX, Optimized WCK Operation, and Alternative-Data-Bus

Graphic DRAMs have been developed to increase maximum I/O interface speeds to satisfy the demand of high-performance graphic applications [1]–[5]. Recently, PAM4 signaling was utilized to increase the I/O bandwidth up to 22Gb/s/pin [5]. However, the reduced voltage margin of PAM4, compared to NRZ, complicates circuit design; margins also become worse with a reduced power supply. This paper achieves 27Gb/s in NRZ, a 1.5× speed enhancement, by improving on previous GDDR6 [3]. A T-coil is designed, for the first time in a DRAM process, so that the maximum operation frequency is increased. The proposed merged-MUX TX increases the maximum speed and reduces power and area consumption. A quad-skew training technique enables a wider clock sampling margin for WCK: up to 3ps, which is 8.1% of 1UI at 27Gbp/s/pin. Furthermore, a dual-mode frequency divider allows a wide-range operation from sub-1Gb/s/pin to 27Gb/s/pin. An alternative-data-bus (ADB) is proposed to solve the frequency limit of the data bus.