Alliance Memory – High-speed DDR2 SDRAM chip offers 2Gbit capacity


The AS4C128M16D2 from Alliance Memory is a high-speed CMOS Double Data Rate 2 Synchronous DRAM (DDR2 SDRAM) which provides 2Gbits of data storage in an 84-ball, 8mm x 12.5mm x 1.2mm FBGA package

The device provides a reliable, pin-compatible drop-in replacement for a number of similar products available today.

The AS4C128M16D2 DDR2 DRAM is organised as eight banks of 16 x 16Mbits. It achieves high data-transfer rates by employing a chip architecture which pre-fetches multiple bits and then synchronises the output data to a system clock.

The chip is designed to meet key DDR2 SDRAM requirements:
• Posted Column Access Strobe (CAS) with additive latency
• Write latency = Read latency-1
• On-Die Termination (ODT)

All of the control and address circuits are synchronised with the positive edge of an externally supplied clock. I/Os are synchronised with a pair of bi-directional strobes in a source-synchronous fashion.

Operating the eight memory banks in an interleaved fashion allows random access operation to occur at a higher rate than is possible with standard DRAMs. A sequential and gapless data rate is possible depending on burst length, CAS latency and the speed grade of the device.

All variants are available in commercial, 0°C to 85°C, and industrial, -40°C to 95°C, temperature ranges. An automotive temperature range of -40°C to 105°C is available on some parts. The functionally equivalent AS4C128M16D2A, fabricated in a different location from the AS4C128M16D2, is also available to give customers confidence in the parts’ continuity of supply.


  • Single 1.8V power supply
  • 400MHz clock rate
  • 800Mbits/s data rate per pin
  • Programmable Read or Write burst lengths of 4 or 8
  • Easy-to-use Refresh functions
  • Programmable mode and extended mode registers


  • Automotive systems
  • Industrial equipment
  • Consumer devices
  • Networking equipment
  • Medical products
  • Embedded systems