Details
![Michael Pietzko Headshot](https://confcats-catavault.s3.amazonaws.com/CATAVault/ieeecass/master/files/styles/cc_user_photo/s3/user-pictures/12192.jpg?h=7d88842e&itok=8JcTbcwr)
- Affiliation
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AffiliationUniversity of Ulm
- Country
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CountryGermany
Excess loop delay (ELD) in high speed continuous-time (CT) Delta-Sigma-Modulators (DSMs) imposes design challenges and limits the use of high resolution, e.g. successive-approximation-register (SAR) based internal quantizers, as usual compensation techniques like the use of a direct path around the quantizer come with increased swings and reduced maximum stable amplitude (MSA). In this paper, two bitwise ELD compensation approaches applicable to cascade-of-integrators with distributed feedback (CIFB) loop filters are proposed, which alleviate this problem for SAR and other multistep quantizers by sequentially feeding bits into the feedback loop when they are available (MSB first, LSB last). Loop-filter equivalence for such bitwise ELD compensation is analytically derived. System-level simulations using Matlab & Simulink for exemplary 4-bit 2nd, 3rd and 4th-order modulators show 40% reduction of the last integrator output swing compared to the conventional direct path compensation. This potentially allows to avoid the swing, quantizer scaling and noise trade-offs due to ELD in state of the art designs.