The CM3109 is a sinking and sourcing regulator specifically designed for series-parallel bus termination for high speed chip set buses as well as DDR memory systems. It can source and sink current up to 2A with high accuracy of 0.5 %. The VTT output voltage is selectable by VDDQSEL and FSBSEL pins. The VDDQSEL pin controls whether the CM3109 is in DDR memory mode with VTT = VDDQ/2, or in FSB mode. In FSB mode, FSBSEL controls whether VTT is 1.225V or 1.45V. This allows the same chip to be used in two different circuits on PC motherboards that support both Northwood and Prescott processors.