Fault Sensitivity Analysis and Reliability Enhancement of An(12)

Abstract — Reliability of systems used in space, avionic and biomedical applications is highly critical. Such systems consist of an analog front-end to collect data, an Analog-to-Digital Converter (ADC) to convert the collected data to digital form and a

0.025

"All 73 nodes"

"4 nodes""8 nodes""12 nodes"

0.025

"All 73 nodes"

"4b""8b"0.02

0.02

1.008

0.015

1.02

0.015

POF

0.01

POF

4.00

1.21.381.51

0.01

0.005

0.005

4.00

1.51

1

2

3

4

5

6

12350

Sizing FactorSizing Factor

Fig.32.Sensitivityvariationwithselectivenoderesizingwithinjectionlevelboundedby1pC(thenumberonthecurvesindicatethecorrespondingfault-sensitiveareaincreasefactor)q=14,r=4

0.0450.040.0350.03

Fig.35.Sensitivityvariationwithselectivenoderesizing(injectionlevelboundedby1pC)q=14,r=4

0.045

"All 73 nodes"

"4 nodes""8 nodes""12 nodes"

0.040.0350.03

1.05All 73 nodes

4b nodes8b nodes12 nodes

1.641.86

POF

0.0250.020.015

POF

0.0250.020.0150.01

0.010.005

6.00

1

2

3

4

5

0.005

01

2

3

4

5

6

Sizing Factor

Sizing Factor

Fig.33.Sensitivityvariationwithselectivenoderesizing(injectionlevelboundedby2pC)q=14,r=4

0.070.060.05

Fig.36.Sensitivityvariationwithselectivenoderesizing(injectionlevelboundedby2pC)q=14,r=4

0.07

"4b nodes""8b nodes""12 nodes"

"All 73 nodes"

"4 nodes""8 nodes""12 nodes"

0.060.050.040.030.02

POF

0.040.030.020.010

6.00

POF

0.010

123456

12

Sizing Factor

3456

Sizing Factor

Fig.34.Sensitivityvariationwithselectivenoderesizing(injectionlevelboundedby4pC)q=14,r=4

Fig.37.Sensitivityvariationwithselectivenoderesizing(injectionlevelboundedby4pC)q=14,r=4

areaoverheadofonly20%.Thenumbersonthecurvesindi-catetheareaincreasefactorforthesizingfactorwhichresultsinthelowestsensitivity.Theabovenodeselectionschemeworkswellforinjectionlevelsboundedby1pC.However,theimprovementisnotsosizeableforhigherinjectionlevelbounds(seeFigures33and34).Thismotivatesasearchforabetternodeselectionschemeandaninsightintowhytheimprove-mentislimitedforhigherinjectionlevels.Theerroroffsetatanodecausedbyaninjectionisdependentamongotherfac-torsontheinjectionlevelandthetransistordrivingstrength.Denoteby Vtheerroneousvoltageoffset,whichisequalto V=IinjRon,whereIinjisthemagnitudeoftheinjectedcurrentandRonistheresistanceposedbythetransistorcon-nectedtothenode. VcanbereducedbyloweringRon,which

canbeachievedbysizingupthetransistor.ButifRonislargethenthetransistorwillhavetobeconsiderablysizedbeforeanygaininsensitivitycanbeachieved.Itisverylikelythatthiskindofnodeswillshowupatthetopofthesortedlistofnodes.Thus,insuchcasesitispossibletoachievehighersensitivitygainswithasmallerareaoverheadbyoptingforanalternatescheme.Inthisschemeonlythemnodesatthebottomofthesortedlistofthenmostsensitivenodesaresized.Notethatsincethemnodesareselectedfromalistofthenmostsensi-tivenodestheyarestillquitesensitive.Figures35,36and37showthatforhigherinjectionbounds,asizeableimprovementinsensitivitycanbeattainedbyoptingforthealternatescheme(seeFigure37,the4band8bcurvesshowthesensitivityvaria-tionwhenmis4and8,respectively,forn=12).Insummary,forlowerinjectionlevels(≤1pC)resizingthenmostsensi-