Presented by : Silicon Mentor

www.siliconmentor.com

Applications of Ultra Low Power Technique On FULL

Adder

Outline INRODUCTION

SOLUTIONS

FULL ADDER

USES OF FULL ADDER

ULTRA LOW POWER DESIGN OF FULL ADDER

DIAGRAM OF ULPFA

ADVANTAGES

8-BIT RIPPLE-CARRY ADDER

CONCLUSION

INTRODUCTION

• Recently, building low-power VLSI systems has emerged as highly in demand because of the fast growing technologies in mobile communication and computation.

• The battery technology doesn’t advance at the same rate as the microelectronics technology.

• There is a limited amount of power Available for the mobile systems.

• We are faced with more constraints: high speed, high throughput, small silicon area, and at the same time, low-power consumption.

HOW WE CAN REDUCE THIS?

• Building low-power, high-performance adder cells is of great interest.

• By suitable power management, particularly as systems spend most of their time in standby mode.

• By design low-power (LP) circuits. This choice closely depends on the design style used.

• Full adders have been investigated by the academic and industrial research communities. The usual performance evaluations are speed, power consumption, and area.

FULL ADDER

• A Full Adder is a combinational digital circuit that performs basic addition of binary inputs;

• Full adder operation provides with Sum (S) and Carry-over (Cout) output;

USES OF FULL ADDER

• Basic building block of on-chip libraries.• Configured according to desired complexity of arithmetic

and numeric computations.• In processors and other kinds of computing devices,

adders are used in the arithmetic logic unit.• Adders also use in other parts of the processor, where

they are used to calculate addresses, table indices, and similar operations.

ULTRA LOW POWER FULL ADDER

• The logic styles used to implement the hybrid adder:

BBL-logic(Branch-Based logic):for carry block.

PT-Logic(Pass Transistor): for sum block

• Implementation of sum block using BBL requires 24 transistors, which is not advantageous.So the sum block has been implemented using pass transistor logic.

BLOCK DIAGRAM

PASS TRANSISTOR : BRANCH BASED LOGIC:

ADVANTAGES OF ULPFA

• implementation of the full-adder with the BBL-PT logic style only 23 transistors are used.

• But in CMOS full adder 28-transistor and in CPL full adder 32-transistor are used.

• So BBL-PT full adder is more advantageous.

Ripple Carry Adder(RCA) Using Full Adder As Basic Cell

• A standard 8-bit Ripple-Carry Adder(RCA) built as a cascade from eight 1-bit full-adders

Circuit Description

• Each full adder inputs a Cin, which is the Cout of the previous

adder. This kind of adder is a Ripple Carry Adder.

• Each carry bit "ripples" to the next full adder.

• Each stage of the adder has to wait until the previous stage

has calculated and propagates its carry output signal.

CONCLUSION

• The power consumption is decrease due to the reduction of transistors.

• The total layout area also reduce.• The packing density is increase because of the less number of

transistor.• The speed and performance of the cell is also increase.• The 8-bit RCA circuit based on the ULPFA achieves both total

and leakage power reductions of more than 50% compared to the 8-bit RCA circuit implemented with a conventional static CMOS full adder.

Contact Us for M.tech/PhD Research Project GuidancePhone : 08130809758

Email: info@siliconmentor.com

THANK YOU