To give some real-world perspective on D/A conversion characteristics, this slide shows the D/A specifications for the Renesas H8S/2148A MCU. Looking at accuracy first with a 4 MOhm load, the absolute accuracy of the D/A converter is ±1.0 LSB for conditions A and B, and ±2.0 LSB for condition C. Here least significant bit (LSB) is a unit of measure, like ns, mA, etc. In this case, 1.0 LSB equates to 1/256th of AVref. So for AVref = 5V; that error is approximately 19 to 20mV. As the slide shows, the D/A is more accurate with a 4 MOhm load than with a 2 MOhm load. This is probably due to the leakage current previously discussed. There may also be a contribution from loading the D/A converter through the analog switch (i.e., the transmission gate provides a direct, un-buffered connection to the D/A circuits). In any case, remember that increased loading of the D/A output decreases accuracy. Also, observe that as the range for Vcc was broadened, AVcc and AVref, the accuracy diminishes. The worst-case Absolute error (sum of all errors) for the D/A in an H8S/2148A MCU is 3.0 LSB, or about 60mV.