DDR Compliance Testing | Granite River Labs

DDR Overview

DDR

Double Data Rate (DDR) is a type of memory technology that has become the de facto standard for computers and other electronic devices to increase performance. DDR SDRAM (Synchronous Dynamic Random Access Memory) means that the memory is synchronized with the system clock and can access any memory location in a random order. DDR has evolved over the years to meet increasing demands for performance and speed. Each major revision of the DDR standard has roughly doubled the memory bandwidth.

DDR transfers data on both the rising and falling edges of the clock signal, so twice per cycle (hence the name). DDR standards have different pin positions, transmission speeds, and power consumption.

JEDEC Association

The JEDEC Solid State Technology Association was established in 1958. It is the leading standards organization for the microelectronics industry. The main goal of JEDEC is to standardize the production, testing, and function definition of products such as solid-state storage (SSD), DRAM, flash memory cards, and radio frequency identification (RFID). For more information, please refer to https://www.jedec.org

The latest version of DDR Specification

JEDEC members may view DDR specifications on this page: https://www.jedec.org/standards-documents

DDR Standards and Nomenclature

GRL’s DDR services typically focus on validating the signal quality performance of a DDR host controller to the JEDEC standard.

DDR Test Process

DDR Test Process

An interposer must be installed at the DRAM component to probe the DDR signals. The interposer may be de-embedded if s-parameters are available. GRL can select and install DDR interposers (billed at cost).

Customer needs to provide:

Exact DQ (data bit), DQS (strobe), and A (address bit) for each part to be tested.
Host controller system
Software tool to generate specific traffic that targets the chip where the DDR interposer is installed to exercise the DQ and Address bits as much as possible for the duration of the test.

The DDR traffic requirements are:

DDR Writes only with random data and burst of no less than 8-words. The data is required to be random to get as many ‘b0 and ‘b1 as possible in burst transaction for the application to build a DDR Eye. DDR5 requires at least 200 CK cycles for any traffic generation.
DDR Reads only with random data and burst of no less than 8-words. The script could have a random write performed to a designated location and then start infinite burst reads.
DDR Write/Read bursts in alternative mode is the best traffic to be used for testing against JEDEC Specification

DDR Test Items & Instruments Used

DDR Test Items

DDR 2-3/LPDDR 2-3:

Set 1 - DQ/DQS Reads and Writes, CS#, and Clock
Set 2 - Address, CAS#, RAS#, and WE#

DDR 5/DDR 4/LPDDR 4/LPDDR 4x:

Differential configuration: Clock#, DQS#, DQ-x Reads and Writes, Command (Address-x or CS#)
(optional) Single-ended configuration: Clock and/or DQS

LPDDR 5:

Differential configuration: Clock#, RDQS#, DQ-x Reads and Writes, and WCK#
(optional) Single-ended configuration: Clock#, RDQS#, and/or WCK#
(optional) Receiver physical layer

The test budget can be checked by restricting to Write transactions only (at DIMM) or Read transactions only (at Host), or reducing the test matrix.

DDR Test Equipment

Keysight or Rohde & Schwarz RTP 16GHz real-time oscilloscope
Differential probes
DDR conformance test automation software

DDR Conformance Testing

DDR Overview

DDR Test Process

DDR Test Items & Instruments Used