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Published byAlfred Harrison Modified over 9 years ago
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16 Bit Logarithmic Converter Tinghao Liang and Sara Nadeau
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16 Bit Logarithmic Converter Introduction Motivation Algorithm Explanation High level description Block diagram Design strategy Baseline performance Performance goals Improvement strategy Improved performance Layout Conclusions and Future Work
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Project Motivation Logarithmic converters simplify computational needs Multiplication/Division -> Addition/Subtraction Power/Root -> Multiplication/Division Real time DSP becoming more and more in demand, increased need for log converters to simplify computation demands Explore interesting circuitry
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Algorithm Whole number portion of base two logarithm of binary input acquired by detecting leading 1 Decimal portion of base two logarithm of binary input approximated by mantissa Ex: Input -> 29 10 or 11101 2 Binary answer -> 100.1101 Decimal answer -> 4.8579 Error -> 0.0454, or 0.9%
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Implementation – Block Diagram
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Baseline Design Strategy Direct CMOS implementation of all circuit blocks Use gates sized for matching rise and fall times from lab 2 Goal – functional circuitry
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Implementation – Leading One Detector Functionality LOD4LOD16
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Implementation – ROM Functionality
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Implementation – Barrel Shifter Functionality
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Baseline Design Results 50 MHz operation speed 5 mW power consumption
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Improvement Strategy - Speed Critical path MSB’s pass through LOD and ROM prior to output LSB’s need valid ROM output before barrel shifter output is valid Critical block – 2:1 MUX Appears in LOD as well as barrel shifter, often cascaded Sized with logical effort 4-Input NOR also resized for minimum average delay
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Improvement Strategy - Power Power supply reduced to 2 V Circuitry simplified ROM circuit activated only when clock is low
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Improvement Strategy - Functionality Expanded from 8 bits to 16 bits Added a flag to indicate zero input
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Schematic Changes - MUX
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Improved Design Results 77 MHz operation speed 1.7 mW power consumption
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Layout – Register
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Layout – Leading One Detector
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Layout - ROM
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Layout – Barrel Shifter
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Improved Design Layout
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Conclusions and Future Work Conclusions Functional base two log converter designed and simulated successfully Speed and power consumption were both improved by design modifications Improvements Size ROM cell for better speed Further optimize layout organization Add error compensation circuitry Build anti-logarithmic converter
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Thank you! Questions?
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