Row-Based Dual Vdd Assignment, for a Level Converter Free CSA Design and Its Near-Threshold Operation

Dipankar Saha, Aanan Chatterjee, Sayan Chatterjee, C. K. Sarkar

Subthreshold circuit designs are very much popular for some of the ultra low power applications, where the minimum energy consumption is the primary concern. But, due to the weak driving current, these circuits generally suffer from huge performance degradation. Therefore, in this paper, we primarily targeted to analyze the performance of a Near-Threshold Circuit (NTC), which retains the excellent energy efficiency of the subthreshold design, while improving the performance to a certain extent. A modified row-based dual Vdd 4-operand CSA (Carry Save Adder) design has been reported in the present work using 45 nm technology. Moreover, to find out the effectiveness of the near-threshold operation of the 4-operand CSA design; it has been compared with the other design styles. From the simulation results, obtained for the frequency of 20 MHz, we found that the proposed scheme of CSA design consumes 3.009*10-7 Watt of Average Power (Pavg), which is almost 90.9 % lesser than that of the conventional CSA design. Whereas, looking at the perspective of maximum delay at output, the proposed scheme of CSA design provides a fair 44.37 % improvement, compared to that of the subthreshold CSA design.

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