implementation & evaluation of the delta- sigma modulation...
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Implementation & Evaluation of the DeltaImplementation & Evaluation of the Delta--Sigma ModulationSigma Modulation--Based BIST Scheme Based BIST Scheme for Sampledfor Sampled--Data MixedData Mixed--Signal SystemsSignal Systems
H.H.--C. HongC. Hong‡‡, J., J.--L. HuangL. HuangTim ChengTim Cheng , C., C.--W. W. WuWu ‡‡
ECE,ECE, UnivUniv. of California, Santa Barbara . of California, Santa Barbara EE Dept., EE Dept., Tsing HuaTsing Hua University, Taiwan University, Taiwan ‡‡
Jun. 2001 2
DSPDSP--based v.s. analog ATEbased v.s. analog ATEIncreased test throughputIncreased test throughput
Reduced switching & settling Reduced switching & settling timetime
Device response is memorized Device response is memorized and analyzed for different and analyzed for different parametersparameters
Software DSP doesn’t have to Software DSP doesn’t have to be realbe real--timetime
Performance limited by Performance limited by ADC/DACADC/DAC
Research Directions Research Directions --DSPDSP--based selfbased self--testing of analog componentstesting of analog components
DSP-based ATE
ADCDAC AnalogDUT
Memory
Digital signal processing
Synchronization
SOC
ADCDAC AnalogCUT
Memory
Digital signal processing
Synchronization
DSP/Processor core
DSPDSP--based BIST based BIST -- onon--chip chip testertester
Relieve the need of expensive Relieve the need of expensive ATEATEReduce external noiseReduce external noise
Practical issuesPractical issuesTest quality limited by Test quality limited by DAC/ADCDAC/ADCDAC/ADC are not always DAC/ADC are not always available, and must be tested available, and must be tested firstfirst
1-bit DAC
1-bit DSM
Jun. 2001 3
Delta-sigmamodulation
fs >> 2fo
DeltaDelta--Sigma ModulationSigma Modulation
High sampling rate (High sampling rate (ffss >> 2f>> 2foo), low output amplitude resolution), low output amplitude resolutionAverage output tracks input valueAverage output tracks input value
Allows the use of relatively “imperfect” componentsAllows the use of relatively “imperfect” componentsSuitable for VLSI implementationSuitable for VLSI implementation
fo Hz
modulationnoise
Hzfo
Analog input Digital output
Jun. 2001 4
1-bit Softwaredelta-sigmamodulator
DeltaDelta--sigma Modulation Based Signal sigma Modulation Based Signal Generation Generation [Roberts][Roberts]
N-bit DACo/p levels
1-bit DAC
Digital signal processing
1+ bit in DAC 1+ bit in DAC 6dB SNR gain6dB SNR gain
How to measure the DAC output levels using onHow to measure the DAC output levels using on--chip chip
resources?resources?
Jun. 2001 5
1-bit ∆Σmodulator1-bit ∆Σ
modulator
AnalogCUT
AnalogCUT
Low-res. DAC& LPF
Low-res. DAC& LPF
Responseanalysis
Programmablecore + memory
Test stimuli& spec.
Pass/fail ?
Software ∆Σmodulator
DeltaDelta--Sigma Modulation Based Sigma Modulation Based BIST ArchitectureBIST Architecture
ATEATE DUTDUT
Jun. 2001 6
The test chip The test chip -- block diagramblock diagram
Stage 1 Stage 21-bit DA
Ext. signalsource
DUT: 2nd-order LPF
DSM 1
DSM 2
Patterngenerator
DSP
Jun. 2001 7
The test chipThe test chip
DUT: 2ndDUT: 2nd--order LPForder LPFDifferential, sampledDifferential, sampled--data implementation (@ 5 MHz)data implementation (@ 5 MHz)
BIST circuitryBIST circuitry11--bit DACbit DAC
Analog Analog multiplexermultiplexer
11--bit 1st/2nd DSM (DSM1/DSM2)bit 1st/2nd DSM (DSM1/DSM2)
Area (mmArea (mm22))
DUTDUT DSM1DSM1 DSM2DSM2
0.7190.719 0.2270.227 0.3630.363
11--bit DACbit DAC
0.0020.002
Area/DUTArea/DUT 11 0.3160.316 0.5040.5040.0030.003
Jun. 2001 8
The DUT specificationThe DUT specificationDesigned sampling rate: 5 MHzDesigned sampling rate: 5 MHz
1st-order output2nd-order output
103 104 105 106
Frequency Response
Jun. 2001 9
The experimentsThe experiments
Performance validation of the Performance validation of the DSMsDSMsUtilize external precision signal generatorUtilize external precision signal generator
Not needed in real test applicationNot needed in real test application
SingleSingle--tone test (STT)tone test (STT)High spectral purity test signalHigh spectral purity test signal
For DR, SNR, and SNDRFor DR, SNR, and SNDR
MultiMulti--tone test (MTT)tone test (MTT)For IMD and FRFor IMD and FR
Jun. 2001 10
Stimulus synthesis Stimulus synthesis -- single tonesingle tone4th4th--order synthesizer: 64 order synthesizer: 64 kbitskbits, 2 , 2 KHzKHz, , --20 20 dBFS dBFS @ 5 MHz@ 5 MHz
102 103 104 105 106
Jun. 2001 11
Stimulus synthesis Stimulus synthesis -- IMDIMD
1st-order2nd-order4th-order
102 103 104 105 106
Choose the 4th-order synthesizer - lower noise floor
Jun. 2001 12
Stimulus synthesis Stimulus synthesis -- FRFR
1st-order2nd-order4th-order
Choice of synthesizer depends on tones of interest
103 104 105 106
Jun. 2001 13
Stimulus synthesis Stimulus synthesis -- FRFR
1st-order2nd-order4th-ordersolid line: STFsymbol: simulation
Choice of synthesizer depends on tones of interest
Jun. 2001 14
The DSM performanceThe DSM performance
82 dB SNDR when < 10 MHz82 dB SNDR when < 10 MHz80 dB SNDR up to 25 MHz80 dB SNDR up to 25 MHz
60 dB SNDR when < 20 MHz60 dB SNDR when < 20 MHz58 dB SNDR up to 25 MHz58 dB SNDR up to 25 MHz
Input: 1 Input: 1 KHz KHz , , --4.6 4.6 dBFSdBFS, OSR: 128, OSR: 128
10 20 30
1st-order2nd-order
Jun. 2001 15
The DSM performanceThe DSM performance
DR of the 1st/2nd DSM: 63 dB/85 dBDR of the 1st/2nd DSM: 63 dB/85 dB(Pass(Pass--band: DC band: DC -- ~100 ~100 KHzKHz))
DR of the 1st/2nd DSM: 65 dB/87 dBDR of the 1st/2nd DSM: 65 dB/87 dB(Pass(Pass--band: DC band: DC -- 20 20 KHzKHz))
Jun. 2001 16
SingleSingle--tone test (STT)tone test (STT)Input: Input: --14 14 dBFSdBFS, 2 , 2 KHzKHz, modulated by 4th, modulated by 4th--order SW DSMorder SW DSMDynamic range is no worse then 65 dB (Dynamic range is no worse then 65 dB (--51 dB @ 10 MHz 51 dB @ 10 MHz -- 14 14 dBFSdBFS))
DUT’s DUT’s DC gainDC gain
SNDRSNDR
DSM1DSM1 DSM2DSM2
5757 7070
SNRSNR 5959 7373
SDRSDR 6161 7373
DRDR 7373 8787
102 103 104 106105
1st-order2nd-orderinput
Jun. 2001 17
MultiMulti--tone test tone test -- IMDIMD66--tone signal, tone signal, --27.4 27.4 dBFS dBFS each, 3X the each, 3X the freqfreq. of previous one. of previous one
102 103 104 106105
1st-order2nd-orderinput
Jun. 2001 18
MultiMulti--tone test (MTT) tone test (MTT) -- FRFR
x: 1st DSMx: 1st DSMo: 2nd DSMo: 2nd DSM
DSM1 is as good as DSM2 for FR analysis.DSM1 is as good as DSM2 for FR analysis.
103 104 105
1st-order synthesizer2nd-order synthesizer4th-order synthesizer
Jun. 2001 19
Diagnosing the DUTDiagnosing the DUTExcessive gain at the first stage: ~3.4 dBExcessive gain at the first stage: ~3.4 dBCause SNDR degradationCause SNDR degradation
103 104 105
1st-order synthesizer2nd-order synthesizer4th-order synthesizer
Jun. 2001 20
Conclusion & future workConclusion & future work
11--bit DSM suitable as onbit DSM suitable as on--chip analog response chip analog response digitizerdigitizer
BaseBase--band, low to medium resolution applicationsband, low to medium resolution applications
DR of DSM1/2 is 63/85 dB for DCDR of DSM1/2 is 63/85 dB for DC--100 100 KHz KHz passpass--bandband
OnOn--going workgoing workValidating techniques for testing the Validating techniques for testing the DSM’sDSM’s
Optimizing the DSP proceduresOptimizing the DSP proceduresSynthesis & analysisSynthesis & analysis
Jun. 2001 21
The 1The 1--bit DACbit DAC
++VrefVref
--VrefVrefvirtual groundvirtual ground
virtual groundvirtual ground
--
++
ph2dph2dph1dph1dph1ph1
ph2*ph2*DinBDinBph2*Dinph2*Din