AVersatile I/OwithRobust Impedance Calibration forVarious MemoryInterfaces

A versatile I/Obuffer isproposed tointerface compensate fortheprocess, voltage andtemperature DDR/DDR2/GDDR3 memorytypes. A newrobust impedance variations aswellastoaccommodate different interfaces. calibration scheme whichfills therole ofoff-chip driver(OCD) and on-die terminator(ODT) forimproving signal integrity isintroduced. A. Versatile IJOBuffer Scheme Theproposed calibration scheme minimizes quantization error and Tosatisfy thesignal integrity requirements foroperation maintains 3030Qimpedance within 3%variations. over1Gbps, theOCD iscalibrated bythechipset toobtain accurate driver strength andthedatabusisterminated by