Design Advisory for Spartan-6 MCB - Removal of VCCINT Restrictions to Reach Maximum DDR3 Data Rates

AR#	41520	Search For Another Answer
Topic	MIG
Last Updated	09/07/2011
Status	Active

Description

Previously communicated restrictions on VCCINT to reach the maximum Spartan-6 MCB DDR3 data rates have been removed. These restrictions required a tighter VCCINT voltage range as well as a UCF constraint (CONFIG MCB_PERFORMANCE=EXTENDED;) to set the extended mode in software. Spartan-6 MCB DDR3 interfaces can operate at the maximum data rates under the standard VCCINT range as follows:



This change applies to all Spartan-6 production devices shipped (past, present and future), but does not apply to Engineering Sample (ES) devices.

NOTE: The VCCINT restrictions still exist for DDR2. For full details on the DDR2 restrictions, see (Xilinx Answer 35818).

Solution

The MIG 3.5-3.7 software included the Extended MCB option on the Memory Selection screen. Selecting the option enabled the extended MCB performance range and set the CONFIG MCB_PERFORMANCE=EXTENDED in the generated UCF. Starting with the MIG 3.8 software (to be released with the ISE 13.2 software), the GUI option will be removed and the generated UCF will always contain the CONFIG MCB_PERFORMANCE = EXTENDED constraint setting. While all production devices are now qualified for operation at the maximum DDR3 data rates over the standard VCCINT range (1.14V to 1.26V), the constraint is still required for the ISE timing tools to properly analyze the interface timing and must not be removed from the UCF file.

Until the MIG 3.8 software is available, you can take advantage of the new DDR3 specifications by ensuring that the Extended Performance GUI option is set in the MIG software and that the devices operate within the standard VCCINT voltage specification.