SDRAM

(Synchronous DRAM) A type of dynamic RAM (DRAM) memory chip that has been widely used since the late 1990s. SDRAM chips eliminated wait states by dividing the chip into two cell blocks and interleaving data between them. While a bit in one block is accessed, a bit in the other is prepared for access.

Double Data Rate (DDR)
DDR SDRAM doubles transfer rates by transferring data on both the rising and falling edges of the clock. DDR uses a 184-pin DIMM module in contrast to the 168-pin DIMM of earlier SDRAMs. Laptops use 200-pin SODIMM modules.

DDR2 and DDR3
DDR2 chips increase data rates using various techniques such as on-die termination, which places the terminating transistors that eliminate excess signal noise on the chip itself. DDR3 offers a moderate speed improvement over DDR2, owing to 90 nm fabrication (see feature size).

DDR2 and DDR3 use 240-pin DIMM modules. DDR, DDR2 and DDR3 modules are all keyed differently so that they cannot be inserted into the wrong motherboard slots.

Dual Channel
Chipsets on the motherboard may support two independent memory controllers, which allow access to two memory modules simultaneously (upstream data on one 64-bit channel; downstream data on the other). Channels can be configured as two 64-bit or one 128-bit. Modules must be installed in matched pairs unless the chipset has an option for mismatched modules. See memory module and SGRAM.

In the following list, the single channel speeds are given. If dual channel is implemented, the memory speed and data rates are doubled, and many memory products use the doubled rate in their chip designations.

          Single
       Channel             Single
         Memory              Channel      DIMM
  Type   Speed    Symbol     Data Rate    Module

DDR3   800 MHz  PC3-12800  12.8 GB/sec  240-pin
DDR3   667 MHz  PC3-10600  10.6 GB/sec  240-pin
DDR3   533 MHz  PC3-8500   8.5 GB/sec   240-pin
DDR3   400 MHz  PC3-6400   6.4 GB/sec   240-pin

DDR2   533 MHz  PC2-8500   8.5 GB/sec   240-pin
DDR2   500 MHz  PC2-8000   8.0 GB/sec   240-pin
DDR2   400 MHz  PC2-6400   6.4 GB/sec   240-pin
DDR2   375 MHz  PC2-6000   6.0 GB/sec   240-pin
DDR2   333 MHz  PC2-5300   5.3 GB/sec   240-pin
DDR2   266 MHz  PC2-4200   4.2 GB/sec   240-pin
DDR2   200 MHz  PC2-3200   3.2 GB/sec   240-pin

DDR    266 MHz  PC-4200    4.2 GB/sec   184-pin
DDR    200 MHz  PC-3200    3.2 GB/sec   184-pin
DDR    166 MHz  PC-2700    2.7 GB/sec   184-pin
DDR    133 MHz  PC-2100    2.1 GB/sec   184-pin
DDR    100 MHz  PC-1600    1.6 GB/sec   184-pin


                         Single Channel
                         Speed

SDRAM  133 MHz            1.1 GB/sec   168-pin
SDRAM  100 MHz            800 MB/sec   168-pin

Matched Slots for Dual Channel
Motherboards that support dual channel use color coded memory slots so that module pairs are inserted properly. This example shows three pairs (one orange and two lavender). (Image courtesy of Giga-byte Technology Company Ltd., www.giga-byte.com)

A Little Nostalgia
This is 12 bits of magnetic core memory from the Whirlwind computer of the early 1950s and is about a quarter inch square in size. Today, that much space holds hundreds of millions of bits. (Image courtesy of The MITRE Corporation Archives.) SDRAM Continues to Deliver Desired Features and Flexibility Why complicate your design? If a simple, cost-effective SDRAM solution will do, plug it in and go. You already know it’s a reliable part. You know it’s got all the features you’re looking for. Plus it’s a long-term solution. We have plans to support it for years to come so it’s still a good fit for products with long life cycles. Our 3.3V SDRAM family offers plenty of options. In fact, we have one of the broadest offerings in the industry today. Choose from four densities (64Mb, 128Mb, 256Mb, and 512Mb), extended operating temperatures (commercial, industrial, and automotive), and various clock rates, cycle times, and package types to get just what you need. Start by using our configurable SDRAM part catalog where you can sort parts by density, pin count, operating temp, or other attributes and order samples of some of our most popular SDRAM devices. You might also want check out our low-power, automotive temp Mobile SDRAM products and see how they match up with your memory requirements. SDRAM Part Catalog and Documentation SDRAM SDRAM Technical Notes SDRAM FAQs Order SDRAM Online SDRAM is the just-right solution for many applications. If it’s what you need for your design, you can order sample quantities of our most popular SDRAM devices right here, right now. Just find the SDRAM part you want in our part catalog and then select “add to cart.” To find out more about ordering online, check out the BuyMicron.com FAQs. Or, if you're interested in production quantities, see our list of leading semiconductor distributors. Stable Supply Technical Support Stability, flexibility, and availability are all characteristics that describe an ideal long-term memory solution. Our SDRAM memory is that kind of solution—the kind you need for the long haul to support your established, proven products. And not only do we have the solutions you need, we’ll help you make the best use of the technology. See our SDRAM part catalog for a complete list. With Micron, you get great memory, backed by experienced technical support—from comprehensive data sheets to time-saving simulation models. We have the FAEs and design development tools to make your job easier. You can dive into our technical resources on a do-it-yourself design or you can work with one of our local field applications engineers if your mass-market project presents a unique challenge. Whatever you need to get your design to market faster, easier, and better—we want to deliver it. SDRAM Key Specifications Specification Description Densities 64Mb, 128Mb, 256Mb, 512Mb Configurations x4, x8, x16, x32 Supply Voltage 3.3V Clock Frequencies 133–200 MHz Temperature Ranges 0° to +70°C –40°C to +85°C –40°C to +105°C Packages 54- and 60-ball FBGA 54- and 90-ball VFBGA 54- and 86-pin TSOP