7.2.4.2 DDR_VREF Recommended Circuits

The DDR_VREF pin serves as a voltage reference input for the DDR I/Os when DDR2 or LPDDR external SDRAM memories are used. This pin is not used with SDR or LPSDR SDRAM memories, and must therefore be connected to ground.

The following figures give the recommended schematics for each case: DDR2, LPDDR and SDR/LPSDR.

Figure 7-3. DDR_VREF Recommended Schematic with DDR2-SDRAM

Figure 7-4. DDR_VREF Recommended Schematic with LPDDR-SDRAM

Figure 7-5. DDR_VREF Recommended Schematic with (LP)SDR-SDRAM