This paper deals with the virtual testing environment for analog-to-digital converters (ADCs) employing a novel and powerful extension of the Servo-Loop method. We build an improved version of the Servo-Loop targeted to full transistor-level circuit simulation of static integral and differential ADC non-linearity. In comparison with the conventional implementation, the Servo- Loop version proposed was enhanced by an effective search algorithm. The algorithm was implemented as a versatile Servo-Looper tool written in Verilog-A language which is suitable for direct co-operation with most of the analog and mixed-signal simulators used in industry. The prospective advantage of our approach is the fact that the implementation in Verilog-A creates an ideal opportunity to build a complex environment comprising the virtual testing engine as well as the DUT in the form of circuit-level ADC design or its behavioral model. At this point, the powerful capabilities of the proposed Servo-Looper tool were successfully confirmed by a large simulation set performed on the ADC behavioral model and the full custom ADC design example. The paper presents the most significant results of the ADC simulation procedure.

This paper demonstrates two methods of noise signal generation for ADC testing. Digital pseudo-random number generator based on LFSR and combinations of LFRS are used. The objective of this exploration is to develop device for generation noise signal with uniformly distributed amplitudes. The signal should be used to measure parameters of AD converters using histogram test method.

It is necessary to keep at the disposition test signals with a high spectral purity for series measuring e.g. in the area of metrology or electronics. Commercial signal generators do not satisfy higher requirements in this area. Our contribution describes chances of the improvement of their quality while using of suitable filters. There is described the construction of a special generator with a high spectral purity of a signal.

The paper presents an improved implementation of a method pointed out for the static characterization of the new generation of high resolution Digital to Analogue Converters (DACs). Interesting aspect of this method is that the problem of the signal acquisition with high resolution is shifted to the simpler problem of the signal acquisition with high speed. In particular, the method is based on the comparison of the DAC output voltage with the analogue reference sinusoidal voltage and the detection of the Zero Crossing Sequence (ZCS) of the resulting signal by high speed ADC. The variation of the ZCS respect to that occurring in the sinusoidal reference signal is used to evaluate the DAC transfer characteristic. The improved implementation concerns the proper design characteristics that can be used as selecting criteria of the test equipment. In particular, the substitution of the ADC for the detection of the ZCS by the comparator device is investigated without affecting the accurate detection of the zero crossing. Moreover, the effects of the noise parameters affecting the generator feeding the reference analogue signal, as amplitude and phase noise, on the evaluation of the DAC static characteristic is analysed by considering test equipment using the comparator device and the high speed ADC, alternatively.

The main point of new approach to the theory of sigma-delta modulation is application of a discrete two-values distribution law for a quantization noise instead of a uniform distribution law accepted before. Due to the new approach, the variance (standard deviation in the square) of the quantization noise becomes dependent on input signal by parabolic function. The noise vs. frequency is found for different input signals taking into account all frequency range from zero to half of sampling frequency. Using dependence of standard deviation on input signal and frequency, different characteristics of sigma-delta modulation can be predicted, including SNR. Difference between analytical and simulation results for new theory can be driven to any small value.