Design and Implementation of Faster and Low Power Multipliers

Abstract

A multiplier is one of the key hardware blocks in most digital and high performance systems such as FIR filters, digital signal processors and microprocessors etc. With advances in technology, many researchers have tried and are trying to design multipliers which offer either of the following- high speed, low power consumption, regularity of layout and hence less area or even combination of them in multiplier. Thus making them suitable for various high speed, low power, and compact VLSI implementations. However area and speed are two conflicting constraints. So improving speed results always in larger areas. So here we try to find out the best trade off solution among the both of them.
Generally as we know multiplication goes in two basic steps. Partial product and then addition. Hence in this paper we have first tried to design different adders and compare their speed and complexity of circuit i.e. the area occupied. And then we have designed Wallace tree multiplier then followed by Booth’s Wallace multiplier and have compared the speed and Power consumption in them.
While comparing the adders we found out that Ripple Carry Adder had a smaller area while having lesser speed, in contrast to which Carry Select Adders are high speed but posses a larger area. And a Carry Look Ahead Adder is in between the spectrum having a proper trade off between time and area complexities.
After designing and comparing the adders we turned to multipliers. Initially we went for Parallel Multiplier and then Wallace Tree Multiplier. In the mean time we learned that delay amount was considerably reduced when Carry Save Adders were used in Wallace Tree applications. Then we turned to Booths Multiplier and designed Radix-4 modified booth multiplier and analyzed the performance of all the multipliers.
After that we turned to different methods of power optimization, of which we could only complete a few like we went for designing different recoding schemes and their corresponding partial product generator scheme. After that we designed these recoders and PP generators and found out the time delays and area covered and power consumed by each scheme. We took into consideration that since all the PP generators take a huge amount of area we need to go for simplest of the designs for them and also side by side we need to ensure that we don’t have much switching actions in the circuit.
After this we even modified one of the recoding schemes to lower the delay and power required by the circuit.
The result of our project helps us to make a proper choice of different multipliers in fabricating in different arithmetic units as well as making a choice among different adders in different digital applications according to requirements. All the programs and results have been given in the following sections.

Further work on Low Power Techniques on different multipliers needs to be done in order to make us choose a proper multiplier in accordance with the requirements by making the best possible trade off choice between Speed and Power in different circumstances.