scope:

This document defines the 3DS DDR4 SDRAM specification, including features, functionalities, AC and DC characteristics, packages, and ball/signal assignments. The purpose of this specification is to define the minimum set of requirements for a compliant 8 Gbit through 128 Gbit for x4, x8 3DS DDR4 SDRAM devices. This addendum was created based on the JESD79-4 DDR4 SDRAM specification. Each aspect of the changes for 3DS DDR4 SDRAM operation was considered. Any TBD's, as of the publication of this document, are under discussion by the formulating committee.

The requirement for 3DS devices compliant to this spec addendum is to have a single electrical load for the stacked devices no matter if the stack is comprised of 2, 4 or 8 devices. The I/O buffer circuitry can be built into the base SDRAM of the stack or into a separate logic buffer device. In either case (built in native circuitry or separate logic die), the assumption is that the I/O buffers are located at the bottom of the stack closest to the package substrate. All pictures and diagrams in the spec depict a master die at the bottom of the stack; it is associated with logical rank 0.