Title :
An internally non-linear ADC for a ΣΔ accelerometer loop
Author :
Schmid, Hanspeter ; Sigel, Sven ; Pastre, Marc ; Kayal, Maher ; Zwahlen, Pascal ; Nguyen, Anne-Marie
Author_Institution :
Inst. of Microelectron., Univ. of Appl. Sci., Windisch, Switzerland
fDate :
May 30 2010-June 2 2010
Abstract :
If an analog-to-digital converter (ADC) is used within a ΣΔ converter such that the loop filter is mixed signal, then the ADC does not need to have the full resolution of the ΣΔ converter, and its input values will not be uniformly distributed over the input range. In this paper, we argue that the best input distribution to use as a general model is the maximum-entropy distribution (for location parameters: the Gaussian distribution). We then describe an externally linear ADC with non-linearly spaced decision boundaries implemented in 0.6μm CMOS and show measurement results of a 19-bit dynamic range ΣΔ accelerometer loop inside which the ADC reaches more than the required 7-bit performance with only 26 decision levels.
Keywords :
accelerometers; analogue-digital conversion; accelerometer loop; analog to digital converter; loop filter; maximum entropy distribution; nonlinear ADC; nonlinear spaced decision boundary; size 0.6 mum; Acceleration; Accelerometers; Analog-digital conversion; Dynamic range; Filters; Force feedback; Gaussian distribution; Mechanical sensors; Probability distribution; Sensor systems;
Conference_Titel :
Circuits and Systems (ISCAS), Proceedings of 2010 IEEE International Symposium on
Conference_Location :
Paris
Print_ISBN :
978-1-4244-5308-5
Electronic_ISBN :
978-1-4244-5309-2
DOI :
10.1109/ISCAS.2010.5537224