low voltage temperature sensor front end
DESCRIPTION
Final Project Presentation for "Design and Analysis of Analog ICs"TRANSCRIPT
Low Voltage Smart Temperature Sensor Front End
Design and Analysis of Analog IC
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Shreyas Rao
R10357881
Satyabh Mishra
R10322331
Introduction
PTAT
Analog to
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Voltage Reference
Analog to Digital Converter
Project Goals
� To Design a PTAT, varying with Temperature but independent of Power Supply.
� To Design a Voltage Reference Independent of
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� To Design a Voltage Reference Independent of Temperature and Power Supply.
� Desired Temperature Range (0ºC~120ºC).
� Desired Voltage Range (1.2V~2V).
Design Principles
� Use of Subthreshold MOSFETs, where VGS < VTH.
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� Achieved by increasing the Transistor Size(W/L) under a fixed current.
Design Principle For PTAT
� By Using the two NMOS in Subthreshold Region.
The Output Current of the PTAT varies exponentially.
� Id=Io exp (Vgs/ζ Vt)
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� Id=Io exp (Vgs/ζ Vt)
;Vt=KT/q
� Transistor size is determined by keeping the PMOS in Active and NMOS in Subthreshold Region.
PTAT Output
Id=Io exp (Vgs/ζ Vt)
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Design Principle for Voltage Ref.7
Design of Compensation Circuit
� The Compensation Current flowing through the resistor equals (VGS /R).
� As the temperature increases , for keeping the
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increases , for keeping the Vgs constant under subthreshold the Compensation Current Decreases.
Compensation Circuit Output9
Final Schematic and Layout10
(167.250µm * 56.850µm)
Voltage Reference11
Voltage Reference12
Temperature VDD
Performance at Worst Corner
V=0.8V
PTAT ResponseVoltage Reference
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Vref at 3V and 5V14
Design Challenges
� Keeping the Desired Transistors in Subthreshold Region and Others in Active Region.
� Determining the Correct (W/L) configuration for all
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� Determining the Correct (W/L) configuration for all transistors and Resistance Value.
� Making the PTAT and Vref independent of Power Supply Variation.
Point of Concern
� The Voltage Reference and PTAT is not independent with variation of Power Supply.
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� Getting the Exact Inverse Slope for PTAT and Compensation Circuit.
Future Work
� Design of PTAT source independent of Power Supply variation.
� An improved constant Gm Circuit with the property
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� An improved constant Gm Circuit with the property of PTAT can be implemented.
� Increasing the Voltage and Temperature Range.
References
� Po-Hsuan Huang, Hongchin Lin and Yen-Tai Lin, “A Simple Subthreshold CMOS Voltage Reference Circuit with Channel-Length Modulation Compensation,” IEEE Transactions on Circuits and Systems-II, September 2006.
� B. Razavi, “Design and Analysis of CMOS Integrated Circuits”.
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� B. Razavi, “Design and Analysis of CMOS Integrated Circuits”. (Text Book)
� G.Giustolisi, G.Palumbo, M.Criscione and F. Cutri, ”A Low-Voltage Low-Power Voltage Reference Based on Subthreshold MOSFETs,” IEEE Journal of Solid State Circuits, VOL.38, January 2003.
Thanks
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Thanks