7.1.2.3.2 16-Bit DDR3L Interface

Note that the 16-bit wide interface schematic is practically identical to the 32-bit interface (see Figure 7-2 and Figure 7-3); only the high-word DDR memories are removed and the unused DQS inputs are tied off.

When not using all or part of the DDR EMIF, the proper method of handling the unused pins is to tie off the DDR3_DQS*_Pi pins to ground via a 1k-Ω resistor and to tie off the DDR3_DQS*_Ni pins to the corresponding DVDD_DDR supply via a 1k-Ω resistor. This needs to be done for each byte not used. Although these signals have internal pullups and pulldowns, external pullups and pulldowns provide additional protection against external electrical noise causing activity on the signals.

The DVDD_DDR, DVDD_DDRDLL, and DDR3_VREFSSTL power supply pins need to be connected to their respective power supplies even if the DDR EMIF is not being used. All other DDR EMIF pins can be left unconnected.

Note: The only DDR EMIF configurations supported are 32-bits wide, 16-bits wide, or not used.

Figure 7-2 32-Bit, One-Bank DDR EMIF Interface Schematic Using Two 16-Bit DDR3L Devices

Figure 7-3 32-Bit, One-Bank DDR EMIF Interface Schematic Using Four 8-Bit DDR3L Devices