Data Converter

Figures of Merit (FoMs)

B. Murmann, "ADC Performance Survey 1997-2022," [Online]. Available: [https://github.com/bmurmann/ADC-survey]

Carsten Wulff, "Advanced Integrated Circuits 2025" [http://analogicus.com/aic2025/2025/02/20/Lecture-6-Oversampling-and-Sigma-Delta-ADCs.html#high-resolution-fom]

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For Scherier FoM (DR, SNDR)

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Quantization Noise

Quantization Error

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Notice \(e_q\in (0, \Delta)\) and its average is \(\Delta/2\). To calculate SNDR, DC component shall be excluded

Don't confuse resolution \(\Delta\) with Bounded Quantization Noise \(-\Delta/2 \sim \Delta/2\)

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Quantization Noise Spectrum

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Quantization noise is less with higher resolution as the input range is divided into a greater number of smaller ranges

This error can be considered a quantization noise with RMS

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ADC Input Noise

Walt Kester, ADC Input Noise: The Good, The Bad, and The UglyΒ­. Is No Noise Good Noise? [link] [pdf]

β€”, MT-004: The Good, the Bad, and the Ugly Aspects of ADC Input Noise-Is No Noise Good Noise? [https://www.analog.com/media/en/training-seminars/tutorials/mt-004.pdf]

Understanding ADC Noise for Small and Large Signal Inputs for Receiver Applications [https://www.analog.com/en/resources/technical-articles/understanding-adc-noise-for-small-and-large-signal-inputs-for-receiver-applications.html]

The LSB determines the ADC code resolution, but the minimum reliably detectable input voltage is determined by the total noise floor, including quantization noise

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[https://share.google/aimode/aA1V4uj3GofKbBojl]

ADC quantization noise is considered a "deterministic error" rather than random thermal noise because it correlates with the input signal, creating a saw-tooth error waveform rather than random Gaussian noise. While it cannot be reduced by averaging a static signal, it can be reduced through averaging if the signal is oversampled, or if dither (random noise) is added to decorrelate it.

Quantization is NOT Noise

[https://analogicus.com/aic2025/2025/02/20/Lecture-6-Oversampling-and-Sigma-Delta-ADCs.html#quantization]

N. Blachman, "The intermodulation and distortion due to quantization of sinusoids," in IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 33, no. 6, pp. 1417-1426, December 1985 [https://sci-hub.st/10.1109/TASSP.1985.1164729]

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The quantization noise is an infinite sum of input signal odd harmonics, where the amplitude of the harmonics is determined by a sum of a Bessel function

"Quantization noise is white", because for a high number of bits, it looks white in the FFT

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[https://share.google/aimode/aA1V4uj3GofKbBojl]

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Sampling Noise in ADC

Kwantae Kim, Integrated Analog Systems D - Lecture 12 (ADC) [https://youtu.be/NkSitVkPNig]

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In the power domain, \(\color{red}v_{nS,RMS}/3 \lt \sigma_{q,RMS}\) ensures that sampling noise power is nearly an order of magnitude smaller than the quantization noise

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ADC Linearity (DNL/INL)

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missing code

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TODO πŸ“…

  • Endpoint method
  • BestFit method

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INL/DNL Measurements for High-Speed Analog-to Digital Converters (ADCs) [https://picture.iczhiku.com/resource/eetop/sYKTSqLfukeHSmMB.pdf]



Code Density Test

Apply a linear ramp to ADC input

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DAC Linearity (DNL/INL)

DAC DNL

One difference between ADC and DAC is that DAC DNL can be less than -1 LSB

In a DAC, DNL < -1LSB implies non-monotonicity

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DAC INL

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The worst INL of three DAC Architecture is same

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  • \(A = \sum_{j=1}^k I_j\), \(B=\sum_{j=k+1}^N I_j\)
  • A and B are independent with \(\sigma_A^2 = k\sigma_u^2\) and \(\sigma_B^2=(N-k)\sigma_u^2\)

Therefore \[ \mathrm{Var}\left(\frac{X}{Y}\right)\simeq \frac{k^2}{N^2}\left(\frac{\sigma_i^2}{kI_u^2} + \frac{\sigma_i^2}{NI_u^2} -2\frac{\mathrm{cov}(X,Y)}{kNI_u^2}\right) \] and \[\begin{align} \mathrm{cov}(X,Y) &= E[XY] - E[X]E[Y] = E[A(A+B)] - kNI_u^2 \\ &= E[A^2]+E[A]E[B] - kNI_u^2= \sigma_A^2+E[A]^2 + k(N-k)I_u^2 - kNI_u^2\\ &= k\sigma_i^2 + k^2I_u^2+ k(N-k)I_u^2 - kNI_u^2 \\ &= k\sigma_i^2 \end{align}\]

Finally, \[ \mathrm{Var}\left(\frac{X}{Y}\right)\simeq \frac{k^2}{N^2}\left(\frac{\sigma_i^2}{kI_u^2} + \frac{\sigma_i^2}{NI_u^2} -2\frac{k\sigma_i^2}{kNI_u^2}\right) = \frac{k^2}{N^2}\left(\frac{1}{k}- \frac{1}{N}\right)\sigma_u^2 \] i.e. \[ \mathrm{Var(INL(k))} = k^2\left(\frac{1}{k}- \frac{1}{N}\right)\sigma_u^2 = k\left(1- \frac{k}{N}\right)\sigma_u^2 \]

Standard deviation of INL is maximum at mid-scale (k=N/2)

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INL/DNL analysis of current steering DAC

Spectral Metrics

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SNR, SNDR (SINAD)

Understanding Key Parameters for RF-Sampling Data Converters White Paper (WP509) [https://docs.amd.com/v/u/en-US/wp509-rfsampling-data-converters]

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ENOB

Qasim Chaudhari, On Analog-to-Digital Converter (ADC), 6 dB SNR Gain per Bit, Oversampling and Undersampling [https://wirelesspi.com/on-analog-to-digital-converter-adc-6-db-snr-gain-per-bit-oversampling-and-undersampling/]

The quantization noise power \(P_Q\) for a uniform quantizer with step size \(\Delta\) is given by \[ P_Q = \frac{\Delta ^2}{12} \] For a full-scale sinusoidal input signal with an amplitude equal to \(V_{FS}/2\), the input signal is given by \(x(t) = \frac{V_{FS}}{2}\sin(\omega t)\)

Then input signal power \(P_s\) is \[ P_s = \frac{V_{FS}^2}{8} \] Therefore, the signal-to-quantization noise ratio (SQNR) is given by \[ \text{SQNR} = \frac{P_s}{P_Q} = \frac{V_{FS}^2/8}{\Delta^2/12}=\frac{V_{FS}^2/8}{V_{FS}^2/(12\times 2^{2N})} = \frac{3\times 2^{2N}}{2} \] where \(N\) is the number of quantization bits

When represented in dBs \[ \text{SQNR(dB)} = 10\log(\frac{P_s}{P_Q}) = 10\log(\frac{3\times 2^{2N}}{2})= 20N\log(2) + 10\log(\frac{3}{2})= 6.02N + 1.76 \]

the maximum achievable SNR of N-bit ADC β€” theoretical SNR limit


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Dan Boschen, GRCon25: Quantifying Signal Quality: Practical Tools for High-Fidelity Waveform Analysis

[linkedin GRCon25]

img

SDR, THD

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Understanding Key Parameters for RF-Sampling Data Converters White Paper (WP509) [https://docs.amd.com/v/u/en-US/wp509-rfsampling-data-converters]

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Walt Kester. Evaluating High Speed DAC Performance [https://www.analog.com/media/en/training-seminars/tutorials/mt-013.pdf]

via other definition

THD: signal to distortion

SINAD: noise and distortion to signal

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SFDR & INL

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Beware, this is of course only true under the same conditions at which the INL was taken, i.e. typically low input signal frequency

Dynamic Range (DR)

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Noise Spectral Density (NSD)

Understanding Key Parameters for RF-Sampling Data Converters White Paper (WP509) [https://docs.amd.com/v/u/en-US/wp509-rfsampling-data-converters]

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Spectral Leakage

Two ways to deal with spectral leakage: Ensure integer number of periods or Windowing

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Coherent Sampling

Choosing M/N non-prime repeats the signal quantization periodically and fewer quantization steps are measured. The quantization repeats periodically and creates a line spectrum that can obscure real frequency lines (e.g. the red lines in the images below, created by non-linearities of the ADC).[https://www.dsprelated.com/thread/469/coherent-sampling-very-brief-and-simple]

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\[ \frac{f_{\text{in}}}{f_{\text{s}}}=\frac{M_C}{N_R} \]

  • \(f_\text{in}\) and \(f_s\) must be incommensurate (\(f_s/f_\text{in}\) is irrational number. btw, co-prime is sufficient but not necessary)

  • \(M_C\) and \(N_R\) must be co-prime

  • Samples must include integer # of cycles of input signal


An irreducible ratio ensures identical code sequences not to be repeated multiple times.

Given that \(\frac{M_C}{N_R}\) is irreducible, and \(N_R\) is a power of 2, an odd number for \(M_C\) will always produce an irreducible ratio

Assuming there is a common factor \(k\) between \(M_C\) and \(N_R\), i.e. \(\frac{M_C}{N_R}=\frac{k M_C'}{k N_R'}\)

The samples (\(n\in[1, N_R]\))

\[ y[n] = \sin\left( \omega_{\text{in}} \cdot t_n \right) = \sin\left( \omega_{\text{in}} \cdot n\frac{1}{f_s} \right) = \sin\left( \omega_{\text{in}} \cdot n\frac{1}{f_{\text{in}}}\frac{M_C}{N_R} \right) = \sin\left( 2\pi n\frac{M_C}{N_R} \right) \]

Then

\[ y[n+N_R'] = \sin\left( 2\pi (n+N_R')\frac{M_C}{N_R} \right) = \sin\left( 2\pi n \frac{M_C}{N_R} + 2\pi N_R'\frac{M_C}{N_R}\right) = \sin\left( 2\pi n \frac{M_C}{N_R} + 2\pi N_R'\frac{kM_C'}{kN_R'} \right) = \sin\left( 2\pi n \frac{M_C}{N_R}\right) \]

So, the samples is repeated \(\color{red}y[n] = y[n+N_R']\)


\(N_R\) & \(M_C\) irreducible ratio (mutually prime)

  • Periodic sampling points result in periodic quantization errors
  • Periodic quantization errors result in harmonic distortion

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GCD(2048, 67)=1

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N = 2048;
cycles = 67;
fs = 1000;
fx = fs*cycles/N;
LSB = 2/2^10;
%generate signal, quantize (mid-tread) and take FFT
xc = cos(2*pi*fx/fs*[0:N-1]);
x = round(xc/LSB)*LSB;
s = abs(fft(x));
s = s(1:end/2)/N*2;
% calculate SNR
sigbin = 1 + cycles;
noise = [s(1:sigbin-1), s(sigbin+1:end)];
snr = 10*log10( s(sigbin)^2/sum(noise.^2) );

% frequency vector
f = [0:N/2-1]/N;
subplot(1,3,1)
stem(f, s);

% some FFT bins for "noise" to be exactly zero, empty plot
subplot(1,3,2)
plot(f, 20*log10(s))

% Use a small offset to avoid -Inf
subplot(1,3,3)
plot(f, 20*log10(s + 1e-6))
ylim([-120, 0])

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Periodic Quantization Noise if N and cycles are not mutually prime, i.e. cycles=64 then GCD(2048, 64)=64, then \(N_R' = 2048/64=32\), so quantization noise manifests as odd harmonics \(n/32\mid n = 2k + 1, k \in \mathbb{Z}\) because of Half Wave Symmetry

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N = 2048;
cycles = 64;
fs = 1000;
fx = fs*cycles/N;
LSB = 2/2^10;
%generate signal, quantize (mid-tread) and take FFT
xc = cos(2*pi*fx/fs*[0:N-1]);
x = round(xc/LSB)*LSB;

% frequency vector
f = [0:N/2-1]/N;
nq = x - xc;
NTn = N / gcd(N, cycles);

subplot(2,1,1)
plot(nq(1:NTn/2), '-s')
hold on
plot(nq(1+NTn/2:NTn), '-o')
xticks(1:1:16); grid on

sn = abs(fft(nq));
sn = sn(1:end/2)/N*2;
subplot(2,1,2)
plot(f, 20*log10(sn))

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Using FFT in Cadence Spectre [https://www.eecis.udel.edu/~vsaxena/courses/ece614/f14/Homeworks/fft_calculation.pdf]

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Offset and Gain Error

Kwantae Kim, Integrated Analog Systems D - Lecture 10 (ADC) [https://youtu.be/IEdbLNJb9wQ]

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1-bit DAC

TODO πŸ“…

\(\Delta \Sigma\) ADC: Linearity

!!PD: Non-linear

Dan Boschen Why use a 1-bit ADC in a Sigma Delta Modulator?. [https://dsp.stackexchange.com/questions/53059/why-use-a-1-bit-adc-in-a-sigma-delta-modulator#comment105988_53063]

Charge Injection and Clock Feedthrough

Slow Gating, Fast Gating

TODO πŸ“…

Midrise and Midtread Quantizers

\(\Gamma_x\) is no-overload range

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Top-Plate vs Bottom-Plate Sampling

[https://class.ece.iastate.edu/ee435/lectures/EE%20435%20Lect%2044%20Spring%202008.pdf]

Bottom-Plate Sampling

Sample signal at the "grounded" side of the capacitor to achieve signal independent sampling

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[https://indico.cern.ch/event/1064521/contributions/4475393/attachments/2355793/4078773/esi_sampling_and_converters2022.pdf]

EE 435 Spring 2024 Analog VLSI Circuit Design - Switched-Capacitor Amplifiers Other Integrated Filters, https://class.ece.iastate.edu/ee435/lectures/EE%20435%20Lect%2044%20Spring%202008.pdf

Top-Plate Sampling

TODO πŸ“…

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Maintain constant common-mode during conversion

D. Pfaff et al., "7.3 A 224Gb/s 3pJ/b 40dB Insertion Loss Transceiver in 3nm FinFET CMOS," 2024 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, USA, 2024 [https://iccircle.com/static/upload/img20240529101747.pdf]

β€”, "A 224Gb/s 3pJ/bit 42dB Insertion Loss Post-FEC Error Free Transceiver in 3-nm FinFET CMOS (Invited)," 2025 IEEE Custom Integrated Circuits Conference (CICC), Boston, MA, USA, 2025, pp. 1-8, doi: 10.1109/CICC63670.2025.10983461.

E. Swindlehurst et al., "An 8-bit 10-GHz 21-mW Time-Interleaved SAR ADC With Grouped DAC Capacitors and Dual-Path Bootstrapped Switch," IEEE Journal of Solid-State Circuits, vol. 56, no. 8, pp. 2347-2359, 2021, [https://sci-hub.se/10.1109/JSSC.2021.3057372]

Track Time

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Finite Acquisition Time - Consider a sinusoidal input

utilizing Laplace transform pair

\[\begin{align} V_\text{in}(t)=\cos{\omega t+\theta} & \overset{\mathcal{L}}{\Rightarrow} \frac{s\cos \theta-\omega \sin \theta}{s^2+\omega^2} \\ h(t) & \overset{\mathcal{L}}{\Rightarrow} \frac{\frac{1}{\tau}}{s+\frac{1}{\tau}} \end{align}\]

Then,

\[\begin{align} V_\text{out}(s) &= V_\text{in}(s)\cdot H(s) \\ &= \frac{s\cos \theta-\omega \sin \theta}{s^2+\omega^2} \cdot \frac{\frac{1}{\tau}}{s+\frac{1}{\tau}} \\ &= \frac{A}{s+\frac{1}{\tau}} + \frac{Bs+C}{s^2+\omega^2} \end{align}\]

Obtain,

\[\begin{align} A &= -\frac{\cos(\theta - \phi)}{\sqrt{\tau ^2 \omega^2 +1}} \\ B & = -A \\ C &= -\frac{\omega \sin(\theta - \phi)}{\sqrt{\tau ^2 \omega^2 +1}} \end{align}\]

That is \[ V_\text{out}(s) = -\frac{\cos(\theta - \phi)}{\sqrt{\tau ^2 \omega^2 +1}} \frac{1}{s+\frac{1}{\tau}} + \frac{1}{\sqrt{\tau ^2 \omega^2 +1}}\frac{s\cos(\theta - \phi) - \omega \sin(\theta - phi)}{s^2+\omega^2} \]

where \(\phi = \arctan(\omega \tau)\)

Boris Murmann, EE315B VLSI Data Conversion Circuits, Autumn 2013 [pdf]

Redundancy

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Max tolerance of comparator offset is \(\pm V_{FS}/4\)

  1. \(b_j\) error is \(\pm 1\)
  2. \(b_{j+1}\) error is \(\pm 2\) , wherein \(b_{j+1}\): \(0\to 2\) or \(1\to -1\)

i.e. complementary analog and digital errors cancel each other, \(V_o +\Delta V_{o}\) should be in over-/under-range comparators (\(-V_{FS}/2 \sim 3V_{FS}/2\))

\[\begin{align} V_{in,j} &= (b_j + \Delta b_j)\cdot \frac{V_{FS}}{2} + \frac{V_{out,j}+\Delta V_{out,j}}{2} \\ V_{in,{j+1}} &= (b_{j+1} + \Delta b_{j+1})\cdot \frac{V_{FS}}{2} + \frac{V_{out,j+1}+\Delta V_{out,j+1}}{2} \end{align}\]

with \(V_{in,j+1} = V_{out,j}+\Delta V_{out,j}\)

\[\begin{align} V_{in,j} &= (b_j + \Delta b_j)\cdot \frac{V_{FS}}{2} + \frac{1}{2} \left\{ (b_{j+1} + \Delta b_{j+1})\cdot \frac{V_{FS}}{2} + \frac{V_{out,j+1}+\Delta V_{out,j+1}}{2} \right\} \\ &= (b_j + \Delta b_j)\cdot \frac{V_{FS}}{2} + \frac{1}{2}(b_{j+1} + \Delta b_{j+1})\cdot \frac{V_{FS}}{2}+ \frac{1}{2}\frac{V_{in,j+2}}{2} \\ &=\tilde{b_j} \cdot \frac{V_{FS}}{2}+ \tilde{b_{j+1}}\cdot \frac{V_{FS}}{4}+ \frac{1}{4}V_{in,j+2} \end{align}\]

where \(b_j\) is 1-bit residue without redundancy and \(\tilde{b_j}\) is redundant bits

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Uniform Sub-Radix-2 SAR ADC

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Minimal analog complexity, no additional decoding effort

Chang, Albert Hsu Ting. "Low-power high-performance SAR ADC with redundancy and digital background calibration." (2013). [https://dspace.mit.edu/bitstream/handle/1721.1/82177/861702792-MIT.pdf]

Kuttner, Franz. "A 1.2V 10b 20MSample/s non-binary successive approximation ADC in 0.13/spl mu/m CMOS." 2002 IEEE International Solid-State Circuits Conference. Digest of Technical Papers (Cat. No.02CH37315) 1 (2002): 176-177 vol.1. [https://sci-hub.se/10.1109/ISSCC.2002.992993]

T. Ogawa, H. Kobayashi, et. al., "SAR ADC Algorithm with Redundancy and Digital Error Correction." IEICE Trans. Fundam. Electron. Commun. Comput. Sci. 93-A (2010): 415-423. [paper, slides]

B. Murmann, β€œOn the use of redundancy in successive approximation A/D converters,” International Conference on Sampling Theory and Applications (SampTA), Bremen, Germany, July 2013. [https://www.eurasip.org/Proceedings/Ext/SampTA2013/papers/p556-murmann.pdf]

Krämer, M. et al. (2015) High-resolution SAR A/D converters with loop-embedded input buffer. dissertation. Available at: [http://purl.stanford.edu/fc450zc8031].

sarthak, "Visualising redundancy in a 1.5 bit pipeline ADCβ€œ [https://electronics.stackexchange.com/a/523489/233816]


Testing

TODO πŸ“…

Kent H. Lundberg "Analog-to-Digital Converter Testing" [https://www.mit.edu/~klund/A2Dtesting.pdf]

Tai-Haur Kuo, Da-Huei Lee "Analog IC Design: ADC Measurement" [http://msic.ee.ncku.edu.tw/course/aic/202309/ch13%20(20230111).pdf] [http://msic.ee.ncku.edu.tw/course/aic/aic.html]

ESE 6680: Mixed Signal Design and Modeling "Lec 20: April 10, 2023 Data Converter Testing" [https://www.seas.upenn.edu/~ese6680/spring2023/handouts/lec20.pdf]

Degang Chen. "Distortion Analysis" [https://class.ece.iastate.edu/djchen/ee435/2017/Lecture25.pdf]

Thermometer to Binary encoder

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Pipeline ADC

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CMP reference voltage is 0.5vref, DAC output is 0.5vref or 0

pipelineADC.drawio

residual error \[ V_{r,n} = (V_{r,n-1}-\frac{1}{2}b_{n})\cdot 2 \] and \(V_{r,-1}=V_i\) \[ V_{r,n-1} = 2^{n}V_i -\sum_{k=0}^{n-1}2^{n-k-1}b_k = 2^{n}\left(V_i - \sum_{k=0}^{n-1}\frac{b_k}{2^{k+1}}\right) \]

here, \(b_0\) is first stage and MSB

It divides the process into several comparison stages, the number of which is proportional to the number of bits

Due to the pipeline structure of both analog and digital signal path, inter-stage residue amplification is needed which consumes considerable power and limits high speed operation

Vishal Saxena, "Pipelined ADC Design - A Tutorial"[https://www.eecis.udel.edu/~vsaxena/courses/ece517/s17/Lecture%20Notes/Pipelined%20ADC%20NonIdealities%20Slides%20v1_0.pdf] [https://www.eecis.udel.edu/~vsaxena/courses/ece517/s17/Lecture%20Notes/Pipelined%20ADC%20Slides%20v1_2.pdf]

Bibhu Datta Sahoo, Analog-to-Digital Converter Design From System Architecture to Transistor-level [http://smdpc2sd.gov.in/downloads/IGF/IGF%201/Analog%20to%20Digital%20Converter%20Design.pdf]

Bibhu Datta Sahoo, Associate Professor, IIT, Kharagpur, [https://youtu.be/HiIWEBAYRJY]


image-20241214164740706

R-2R & C-2C

TODO πŸ“…

Conceptually, area goes up linearly with number of bit slices

drawback of the R-2R DAC


\(N_b\) bit binary + \(N_t\) bit thermometer DAC

R-2R.drawio

\(N_b\) bit binary can be simplified with Thevenin Equivalent \[ V_B = \sum_{n=0}^{N_b-1} \frac{B_n}{2^{N_b-n}} \] with thermometer code

\[\begin{align} V_o &= V_B\frac{\frac{2R}{2^{N_t}-1}}{\frac{2R}{2^{N_t}-1}+ 2R}+\sum_{n=0}^{2^{N_t}-2}T_n\frac{\frac{2R}{2^{N_t}-1}}{\frac{2R}{2^{N_t}-1}+ 2R} \\ &= \frac{V_B}{2^{N_t}} + \frac{\sum_{n=0}^{2^{N_t}-2}T_n}{2^{N_t}} \\ &= \sum_{n=0}^{N_b-1} \frac{B_n}{2^{N_t+N_b-n}} + \frac{\sum_{n=0}^{2^{N_t}-2}T_n}{2^{N_t}} \end{align}\]

B. Razavi, "The R-2R and C-2C Ladders [A Circuit for All Seasons]," in IEEE Solid-State Circuits Magazine, vol. 11, no. 3, pp. 10-15, Summer 2019 [https://www.seas.ucla.edu/brweb/papers/Journals/BR_SSCM_3_2019.pdf]


4bit binary R2R DAC with Ru=1kOhm

RVB equivalent R

image-20241214190045688

Binary-Weighted (BW) DAC

image-20241215094852761

During \(\Phi_1\), all capacitor are shorted, the net charge at \(V_x\) is 0

During \(\Phi_2\), the charge at bottom plate of CDAC \[ Q_{DAC,btm} = \sum_{i=0}^{N-1}(b_i\cdot V_R - V_x)\cdot 2^{i}C_u = C_uV_R\sum_{i=0}^{N-1}b_i2^i - (2^N-1)C_uV_x \] the charge at the internal plate of integrator \[ Q_{intg} = V_x C_p + (V_x - V_o)2^NC_u \] and we know \(-V_x A = V_o\) and \(Q_{DAC,btm} = Q_{intg}\) \[ C_uV_R\sum_{i=0}^{N-1}b_i2^i - (2^N-1)C_uV_x = V_x C_p + (V_x - V_o)2^NC_u \] i.e. \[ C_uV_R\sum_{i=0}^{N-1}b_i2^i = (2^N-1)C_uV_x + V_x C_p + (V_x - V_o)2^NC_u \] therefore \[ -V_o = \frac{2^N C_u}{\frac{(2^{N+1}-1)C_u+C_p}{A}+2^NC_u}\sum_{i=0}^{N-1}b_i\left(2^i\frac{V_R}{2^N}\right)\approx \sum_{i=0}^{N-1}b_i\left(2^i\frac{V_R}{2^N}\right) \]


Midscale (MSB Transition) often is the largest DNL error

image-20241215090447383

\(C_4\) and \(C_1+C_2+C_3\) are independent (can't cancel out) and their variance is two largest (\(16\sigma_u^2\), \(15\sigma_u^2\), ), the total standard deviation is \(\sqrt{16\sigma_u^2+15\sigma_u^2}=\sqrt{31}\sigma_u\)

reference

Maloberti, F. Data Converters. Dordrecht, Netherlands: Springer, 2007.

Ahmed M. A. Ali 2016, "High Speed Data Converters" [pdf]

Razavi B. Analysis and Design of Data Converters. Cambridge University Press; 2025.


Aaron Buchwald, ISSCC2010 T1: "Specifying & Testing ADCs" [https://www.nishanchettri.com/isscc-slides/2010%20ISSCC/Tutorials/T1.pdf]

Ahmed M. A. Ali. CICC 2018: High Speed Pipelined ADCs: Fundamentals and Variants [https://picture.iczhiku.com/resource/eetop/SyIGzGRYsHFehcnX.pdf]

John P. Keane, ISSCC2020 T5: "Fundamentals of Time-Interleaved ADCs" [https://www.nishanchettri.com/isscc-slides/2020%20ISSCC/TUTORIALS/T5Visuals.pdf]

Yun Chiu, ISSCC2023 T3: "Fundamentals of Data Converters" [https://www.nishanchettri.com/isscc-slides/2023%20ISSCC/TUTORIALS/T3.pdf]

β€”οΌŒ "Design and Calibration Techniques for SAR and Pipeline ADCs" [http://formation-old.in2p3.fr/microelectronique15/IN2P3_ADC.pdf]

β€”οΌŒ Radiation-Tolerant SAR ADC Architecture and Digital Calibration Techniques [https://indico.cern.ch/event/385097/attachments/768706/1054353/CERN_May15.pdf]

β€”οΌŒ Recent Advances in Multistep Nyquist ADC's [https://www.eecis.udel.edu/~vsaxena/courses/ece614/Handouts/Recent%20Advances%20in%20Nyquist%20rate%20ADCs.pdf]

Boris Murmann, ISSCC2022 SC1: Introduction to ADCs/DACs: Metrics, Topologies, Trade Space, and Applications [https://www.nishanchettri.com/isscc-slides/2022%20ISSCC/SHORT%20COURSE/SC1.pdf]

β€”οΌŒ ISSCC2012 SC3: Introduction to ADCs/DACs: Metrics, Topologies, Trade Space, and Applications [https://www.nishanchettri.com/isscc-slides/2012%20ISSCC/SHORT%20COURSE/SC3Visuals.pdf]

β€”οΌŒ A/D Converter Figures of Merit and Performance Trends [https://www.nishanchettri.com/isscc-slides/2015%20ISSCC/CIRCUIT%20INSIGHTS/Murmann.pdf]

Aaron Buchwald, ISSCC 2008 T2 Pipelined A/D Converters: The Basics [pdf]

Yohan Frans, CICC2019 ES3-3- "ADC-based Wireline Transceivers" [pdf]

Samuel Palermo, ISSCC 2018 T10: ADC-Based Serial Links: Design and Analysis [https://www.nishanchettri.com/isscc-slides/2018%20ISSCC/TUTORIALS/T10/T10Visuals.pdf]

Ahmed M. A. Ali. ISSCC2021 T5: Calibration Techniques in ADCs [https://www.nishanchettri.com/isscc-slides/2021%20ISSCC/TUTORIALS/ISSCC2021-T5.pdf]

Jan Mulder Broadcom. ISSCC2015 T5: High-Speed Current-Steering DACs [https://www.nishanchettri.com/isscc-slides/2015%20ISSCC/TUTORIALS/ISSCC2015Visuals-T5.pdf]

Zhang, Milin, Zhihua Wang, Jan van der Spiegel and Franco Maloberti. "Advanced Tutorial on Analog Circuit Design." (2023)


M. Gu, Y. Tao, Y. Zhong, L. Jie and N. Sun, "Timing-Skew Calibration Techniques in Time-Interleaved ADCs," in IEEE Open Journal of the Solid-State Circuits Society [https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10804623]

everynanocounts. Memos on FFT With Windowing. URL: https://a2d2ic.wordpress.com/2018/02/01/memos-on-fft-with-windowing/

How to choose FFT depth for ADC performance analysis (SINAD, ENOB). URL:https://dsp.stackexchange.com/a/38201

Computation of Effective Number of Bits, Signal to Noise Ratio, & Signal to Noise & Distortion Ratio Using FFT. URL:https://cdn.teledynelecroy.com/files/appnotes/computation_of_effective_no_bits.pdf

Kester, Walt. (2009). Understand SINAD, ENOB, SNR, THD, THD + N, and SFDR so You Don't Get Lost in the Noise Floor. URL:https://www.analog.com/media/en/training-seminars/tutorials/MT-003.pdf

T. C. Hofner: Dynamic ADC testing part I. Defining and testing dynamic ADC parameters, Microwaves & RF, 2000, vol. 39, no. 11, pp. 75-84,162

T. C. Hofner: Dynamic ADC testing part 2. Measuring and evaluating dynamic line parameters, Microwaves & RF, 2000, vol. 39, no. 13, pp. 78-94

AN9675: A Tutorial in Coherent and Windowed Sampling with A/D Converters https://www.renesas.com/us/en/document/apn/an9675-tutorial-coherent-and-windowed-sampling-ad-converters

APPLICATION NOTE 3190: Coherent Sampling Calculator (CSC) https://www.stg-maximintegrated.com/en/design/technical-documents/app-notes/3/3190.html

Coherent Sampling (Very Brief and Simple) https://www.dsprelated.com/thread/469/coherent-sampling-very-brief-and-simple

Signal Chain Basics #160: Making sense of coherent and noncoherent sampling in data-converter testing https://www.planetanalog.com/signal-chain-basics-160-making-sense-of-coherent-and-noncoherent-sampling-in-data-converter-testing/

Signal Chain Basics #104: Understanding noise in ADCs https://www.planetanalog.com/signal-chain-basics-part-104-understanding-noise-in-adcs/

Signal Chain Basics #101: ENOB Degradation Analysis Over Frequency Due to Jitter https://www.planetanalog.com/signal-chain-basics-part-101-enob-degradation-analysis-over-frequency-due-to-jitter/

Clock jitter analyzed in the time domain, Part 1, Texas Instruments Analog Applications Journal (slyt379), Aug 2010 https://www.ti.com/lit/an/slyt379/slyt379.pdf

Clock jitter analyzed in the time domain, Part 2 https://www.ti.com/lit/slyt389

Measurement of Total Harmonic Distortion and Its Related Parameters using Multi-Instrument [pdf]

Application Note AN-4: Understanding Data Converters' Frequency Domain Specifications [pdf]

Belleman, J. (2008). From analog to digital. 10.5170/CERN-2008-003.131. [pdf]

HandWiki. Coherent sampling [link]

Luis Chioye, TI. Leverage coherent sampling and FFT windows when evaluating SAR ADCs (Part 1) [link]

Coherent Sampling vs. Window Sampling | Analog Devices https://www.analog.com/en/technical-articles/coherent-sampling-vs-window-sampling.html

Understanding Effective Number of Bits https://robustcircuitdesign.com/signal-chain-explorer/understanding-effective-number-of-bits/

ADC Input Noise: The Good, The Bad, and The Ugly. Is No Noise Good Noise? [https://www.analog.com/en/resources/analog-dialogue/articles/adc-input-noise.html]

Walt Kester, Taking the Mystery out of the Infamous Formula, "SNR = 6.02N + 1.76dB," and Why You Should Care [https://www.analog.com/media/en/training-seminars/tutorials/MT-001.pdf]

Dan Boschen, "How to choose FFT depth for ADC performance analysis (SINAD, ENOB)", [https://dsp.stackexchange.com/a/38201]

B. Razavi, "A Tale of Two ADCs - Pipelined Versus SAR" IEEE Solid-State Circuits Magazine, Volume. 7, Issue. 30, pp. 38-46, Summer 2015 [https://www.seas.ucla.edu/brweb/papers/Journals/BRSummer15ADC.pdf)]


Dr. Tai-Haur Kuo (ιƒ­ζ³°θ±ͺ ζ•™ζŽˆ) Analog IC Design (ι‘žζ―”η©ι«”ι›»θ·―θ¨­θ¨ˆ) [http://msic.ee.ncku.edu.tw/course/aic/aic.html]


Converter Passion for data-converter professionals sharing thoughts on ADCs and DACs [https://converterpassion.wordpress.com/]

Boris Murmann, EE315B VLSI Data Conversion Circuits, Autumn 2013 [pdf]


MPScholar Analog-to-Digital Converters (ADCs) [https://www.monolithicpower.com/en/learning/mpscholar/analog-to-digital-converters]

tomverbeure. List of Analog Devices Tutorials [https://tomverbeure.github.io/2021/02/15/Analog-Devices-Tutorials.html]