Slew rate is the measure of how fast an output changes. Because the initial and final stages of the output change can be non-linear, the slew rate is measured during the linear region of  the output transition. Most slew rate measurements are taken in the linear region between ¼ and ¾ scale, removing any possible headroom or footroom issues. Slew rate is specified in volts per micro second and, as can be seen from the output response of the AD5380 DAC shown here, it is the slope of the output’s response.