A 35-GS/s, 4-Bit Flash ADC With Active Data and Clock Distribution Trees
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Bibliographic record
Abstract
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a 35-GS/s, 4-bit flash ADC-DAC with active data and clock distribution trees. At mm-wave clock frequencies, skew due to mismatch in the clock and data distribution paths is a significant challenge for both flash and time-interleaved converter architectures. A full-rate front-end track and hold amplifier (THA) may be used to reduce the effect of skew. However, it is found that the THA output must then be distributed to the comparators with a bandwidth greater than the sampling frequency in order to preserve the flat regions of the track and hold waveform. Instead, if the data and clock distribution have very low skew, the THA can be omitted thus obviating the associated nonlinearities and resulting in improved performance. In this work, a tree of fully symmetric and linear BiCMOS buffers, called a “data tree”, distributes the input to the comparator bank with a measured 3-dB bandwidth of 16 GHz. The data tree is integrated into a complete 4-bit ADC including a full-rate input THA that can be disabled and a 4-bit thermometer-code DAC for testing purposes. The chip occupies 2.5 mm <formula formulatype="inline"> <tex Notation="TeX">$\times$</tex></formula> 3.2 mm including pads and is implemented in 0.18 <formula formulatype="inline"><tex Notation="TeX">$\mu{\hbox {m}}$</tex></formula> SiGe BiCMOS technology. The ADC consumes 4.5 W from a 3.3 V supply while the DAC operates from a 5<formula formulatype="inline"> <tex Notation="TeX">$~$</tex></formula>V supply and consumes 0.5 W. The ADC has 3.7 ENOB with a 3-dB effective resolution bandwidth of 8 GHz and a full-scale differential input range of 0.24 <formula formulatype="inline"><tex Notation="TeX">$V_{pp}$</tex> </formula>. With the THA enabled, the performance degrades rapidly beyond 8 GHz to less than 1-bit, but with the THA disabled, the ENOB remains better than 3-bits for inputs up to 11<formula formulatype="inline"><tex Notation="TeX">$~$</tex> </formula>GHz with an SFDR of better than 26 dB. </para>
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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