VTT Power

VTT is memory bus termination voltage. To maintain noise margins, VTT must be equal to VDDQ/2, with an accuracy of ± 3%. VTT terminates command and address signals to VDDQ/2 using a parallel resistor (RT) tied to a low impedance source.

VTT is not used to terminate any DDR clock pairs. Rather, the xDDR_CLK and xDDR_CLK_N termination consists of a parallel 100-121 Ω resistor between the two lines.