time-to-digital converter architectures using two
TRANSCRIPT
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Time-to-Digital Converter Architectures
Using Two Oscillators
With Different Frequencies
Kosuke Machida, Yuki Ozawa, Yudai Abe
Haruo Kobayashi
Gunma University
Oct. 18, 2018
Session 6B-II
Mixed-Signal IC Designs
and ATE
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Research Objective
Investigation of TDC architectures
with Verner oscillators
● Analog centric one
- Using trigger circuits
- Two oscillators with different frequencies
- No self-calibration required
● Digital centric one
- Two ring oscillators
with different frequencies
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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Time-to-Digital Converter
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TDC Application Examples (1)
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TDC Application Example (2)
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Comparison of TDC Architectures
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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Voltage can be held
Time difference cannot be held
Time difference can be held !
Truth
Myth
Myth and Truth of Time Signal
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Trigger Circuit
t0 t0t0
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T/H Circuit
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Trigger Circuit Waveforms
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Oscillate with initial phase
at input timing
Input START, STOP signal
It can hold the time difference using two trigger circuits
1step 2step 3step 4step 5step 6step 7step
Δ𝑇 Δ𝑇
One-shot Timing Measurement Using Trigger Circuit
Proposal
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SAR-ADC VS. SAR-TDC
SAR ADC : Comparator DAC
SAR TDC : D-FF Delay line
SAR-ADC
SAR-TDC
Y. Ozawa, H. Kobayashi, et. al., “SAR TDC Architecture with Self-Calibration Employing Trigger Circuit,”IEEE Asian Test Symposium, Taipei (Nov. 2017).
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SAR TDC Operation
Example ΔT = 4.3 τ
STEP1
100
1
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SAR TDC Operation
Example ΔT = 4.3 τ
STEP2
110
0
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SAR TDC Operation
Example ΔT = 4.3 τ
STEP3
101
0
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SAR TDC Operation
Example ΔT = 4.3 τ
STEP4 (Stable)
100
100Digital output:4
1
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Low Frequency Clock Measurement
Low frequencySTART
SAR TDC
CLK1
STOP
SAR TDC
CLK2
Short testing time for low frequency repetitive timing
High frequency
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Verner Oscillation TDC
f1: known
f2: known
Start oscillation f1 at START edge
f2 at STOP edge
What about using different frequencies ?
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Verner Oscillation TDC Operation
t0 = f (f1, f2, number of , …, number of , …)
f1
f2
f1≒ f2 Time
resolution
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Usage of Different but Close Frequencies
f1≒ f2
Equivalent
Sampling
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Design Tradeoff
f1
f2
Fine time resolution
Long Measurement timeWide input time range
Tin = 1/f1, 1/f2 Tmeas = Tin x Tin / t’
Tin
Tmeas
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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Proposed TDC Architecture
f1: known
f2: known
# of
# of
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Logic Circuit for Time Measurement
# of
# of
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D1 Sampling by D2
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Counter & Update
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Deviation Points by Time Difference
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Deviation and Time Resolution
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Equivalent Time Sampling
t’=1/f2
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Waveform Reconstruction
Sampled points
rearrangement
High frequency
operation
Low frequency
operation
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Measurement Time Resolution
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Proposed TDC Linearity
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Simulation Verification of Proposed TDC
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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Ring Oscillator with Start
Input
Output
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Digital Centric TDC
Ring oscillator frequencies
f1 Counter 1 output N1 / reference time Tref
f2 Counter 2 output N2 / reference time Tref
f1
f2
≒≒
N1
N2
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Outline
Research Background
Measurement Principle
Analog Centric TDC
Digital Centric TDC
Discussion & Conclusion
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TDC Architecture Comparison
Excellent Good Bad
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Comparison of Time and Voltage
● Dynamic range of time domain signal
can be infinite.
● Time flows in one direction.
● Ring oscillator can be often used
for time domain signal processing.
● Exact frequency division is possible,
whereas exact voltage division is difficult.
● Frequency is a stable signal.
● Jitter is a difficult problem.
● Time as well as voltage can be held.
● Time as well as voltage can be amplified.
● New TDC architectures can be inspired by
existing ADC architectures.
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Conclusion
● Verner Oscillator TDC architectures
- Analog centric and digital centric ones
- Using two oscillators
with different frequencies
Can be shared among multi-channel TDCs
- No delay line
- No self-calibration required
- Design tradeoff
Measurement time
Time resolution
Input time range
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Time is very important !
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Appendix :N-Stage Trigger Circuit
S. Sakurai, H. Kobayashi, et. al., “Study OF Multi-Stage Oscilloscope Trigger Circuit,”IEEE ISPACS, Xiamen, (Nov. 2017)
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Three-stage Trigger Circuit
Trigger input
Output
c
Track&Hold
Track&Hold
Σ
Input
to
Output
to
sinωt
Track&Hold
sin(ωt+2π/3)
+
+
+
-
-
-
sin(ωt+4π/3)
F1
F2
F3
S1
S2
S3
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Analysis of Three-stage Trigger Circuit
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N-Stage Trigger Circuit
Track&Hold
Track&Hold
Σ
Input
Output
sinωt
Track&Hold
sin(ωt+θ)
+
+
+sin(ωt+2θ)
F1
F2
F3
S1
S2
S3
Track&Hold
Sn
sin(ωt+nθ)
Σ
Σ
Σ
・・・
・・・
・・・
Fn ・・・
Σ+
Vo_N・・・
to
Trigger circuit is a key !Trigger circuit for TDC T/H circuit for ADC.