Testing low-resolution DACs using the Generalized Morse Sequence as Stimulus Sequence for Cancelling DC drift

For production test and characterization of DACs, the non-linearity is one of the most important values to be measured. For this end, usually a digital ramp signal is applied at the input of the DAC, its output signal is captured and evaluated. Sometimes the measurement is disturbed by drift of the DC offset or low-frequent noise, originating e.g. from the tester´s analog capture instrument or the DAC´s internal reference. In this case, using the Generalized Morse Sequence instead of a ramp as input reduces the effect of DC offset drift on the measurement of the non-linearity. This technique allows for using cheaper analog tester instruments or analog Built-In Self Test (BIST) without loosing accuracy. Simulations were done with a slowly decreasing offset, modeled an exponential decay function. They show a dramatically increase of drift rejection, when using the Generalized Morse Sequence instead of a ramp signal.