Testing of High Resolution ADCs Using Lower Resolution DACs via Iterative Transfer Function Estimation

Linearity testing of high resolution analog-to-digital Converters (ADCs) requires test instrumentation that has high precision digital-to-analog conversion (DAC) capability. Further, a large number of samples need to be collected for linearity testing of high resolution ADCs (18-24 bit) to guarantee test quality. In this paper a novel fast linearity testing approach is proposed for testing high resolution ADCs using a low precision DAC and a potentiometer. A polynomial fit of the transfer function of the ADC is generated using measurements made at intermediate code points. The test setup and analysis procedure makes no assumption about the linearity of the lower precision DAC or the potentiometer used to generate the ADC test stimulus. A least squares based polynomial fitting approach is used to characterize the transfer function of the ADC. The computed transfer function is then used to estimate the Integral Non-Linearity (INL) and the Differential Non-Linearity(DNL) of the system accurately. Software simulations and hardware experiments are performed to validate the proposed methodology.