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Analog-to-Digital Conversion by Digital Control

Analog-to-digital conversion at high speed or with high precision, and with a limited power budget, remains challenging. This note is about a new conversion principle that started with an idea by Georg Wilckens and was developed much further by Hampus Malmberg:

H.-A. L. and G. Wilckens,
Control-based analog-to-digital conversion without sampling and quantization,
2015 Information Theory & Applications Workshop (ITA), San Diego, CA, Feb. 1-6, 2015.
IEEE Xplore / Preprint
H. Malmberg, G. Wilckens, and H.-A. L.,
Control-bounded analog-to-digital conversion,
Circuits, Systems, and Signal Processing, 2022.
pdf
H. Malmberg, T. Mettler, T. Burger, F. Feyling, and H.-A. L.,
Calibrating control-bounded ADCs,
arXiv:2211.06741, 2022.
F. Feyling, H. Malmberg, C. Wulff, H.-A. L., and T. Ytterdal,
Design and analysis of the leapfrog control-bounded A/D converter,
IEEE Trans. Very Large Scale Integration (VLSI) Systems, vol. 32, pp. 79-88, Jan. 2024.
IEEE Xplore
H. Malmberg, F. Feyling, and J. M. de la Rosa,
A control-bounded quadrature leapfrog ADC,
IEEE Trans. on Circuits and Systems I: Regular Papers, vol. 71, pp. 2483-2496, June 2024.
IEEE Xplore
F. Feyling, H. Malmberg, C. Wulff, and T. Ytterdal,
A compiled 7th-order leapfrog ADC in 130 nm CMOS,
Circuits, Systems, and Signal Processing, Oct. 2025,
doi.org/10.1007/s00034-025-03370-9

The idea is to feed the analog signal(s) into a continuous-time linear amplifying filter that is stabilized by digital control, from which a digital filter computes an estimate of the analog signal. Such converters may be viewed as (nontrivial) generalizations of continuous-time sigma-delta converters, but the conceptual perspective is entirely different and opens a much larger design space. The conversion principle is quite simple (unless you try to understand it in terms of traditional concepts), hardware friendly, and amenable to digital calibration. Some first chip designs were carried out by Fredrik Feyling.

Beyond the examples worked out in the papers above, Hampus's PhD thesis points to a more general vision of sensing and acting at the interface between analog and digital.

Last modified: March 28, 2026