Robust Low Power Embedded SRAM Design: From System to Memory Cell

Lowering power consumption and increasing the noise margin have become the two most important aspects to be considered in SRAM design. Additionally, a stable operation with good memory retention capability has gained greater importance in obtaining good yield at low-voltage and low-power SRAM designs, due to the fact that parameter variations play a major role in scaled technologies. In this paper, the 6T SRAM, 7T low power SRAM and 7T multi threshold low power SRAM designs are designed, to incorporate power gating technique. The architecture of each of the SRAM designs and their working are analyzed thoroughly. The outputs of the read, write and hold operations with transient response are observed and the power dissipation and static noise margin (SNM) of the each of the SRAM cells is calculated and compared. The paper also presents new power reduction solution through the cell control circuit which reduces the unwanted and spurious switching activities during read and writes operations. The paper demonstrates the reduction of the power con- sumption through the use of cell control circuit.

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CMOS EIGHT-TRANSISTOR MEMORY CELL FOR LOW-DYNAMIC-POWER HIGH-SPEED EMBEDDED SRAM

Journal of Circuits System and Computers ◽

10.1142/s0218126608004599 ◽

2008 ◽

Vol 17 (05) ◽

pp. 845-863 ◽

Cited By ~ 2

Author(s):

SALEH M. ABDEL-HAFEEZ ◽

ANAS S. MATALKAH

Keyword(s):

High Speed ◽

Average Power ◽

Memory Cell ◽

Timing Synchronization ◽

Substrate Noise ◽

Large Coupling ◽

Average Power Consumption ◽

Sram Design ◽

Simulation Results ◽

Embedded Sram

Embedded SRAM design with high noise margin between read and write, low power, low supply voltages, and high speed become essential features in VLSI embedded applications. The complete embedded SRAM design of self-timing synchronization is proposed based on the CMOS eight-transistor (8T-Cell) memory cell circuit. The cell is based on the traditional six-transistor (6T-Cell) cross-coupled invertors with the addition of two NMOS transistors for separate read buffer circuit. The read buffer structure is based on pre-charging the read bit-line during the low value of read clock and evaluating the read bit-line during the high value of read clock, thereby maintaining one active line per column and eliminating the use of traditional sense amplifier with all its synchronization schemes. The simulation results show that the embedded SRAM of size 128-bit × 128-bit is operating at a maximum frequency of 200 MHz for Write and Read clock cycles with 1.62 V power supply, and measures a total average power consumption of 22.60 mW. All simulation results were conducted on 0.18 μm TSMC single poly and three layers of metals measuring a cell area of 2.2 × 3.0 μ m 2. The circuit is not meant to replace the SRAM with 6T-Cell transistor structure; however, it is attractive for applications related to high density with automation road-map design, such as graphic and network processor chips. In these applications, memory sizes are introduced in many different irregular geometries and uses all over the chip with storage sizes less than 20 k-bit, in addition, it is susceptible to large substrate noise as well as large coupling wire routing.

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