When selecting an ADC, first determine if dual simultaneous sampling is required. By taking simultaneous measurements vs. two successive measurements, the user improves the performance of many 3-phase control algorithms. Simultaneous sampling is also needed when using Resolvers or SinCos encoders. Both Resolvers and SinCos encoders output a sine and cosine wave that need to be measured simultaneously in order to accurately calculate the position and speed of the rotor. The 10 to 12-bit resolution is adequate for most motor control applications, but the higher the resolution, the better the accuracy and therefore the better the motor performance and efficiency. It is very common to find 14 and 16-bit ADCs in high performance motors. In order to synchronize the ADC measurement to the PWM control waveform, the MCU needs to be able to precisely control when the measurement is taken via a precision trigger on the ADC. The MCU triggers a current reading every PWM cycle, at precisely the mid point of the PWM waveform. Reading the current at this point effectively averages out the ripple current, yielding the average current. Finally, having a minimal sample acquisition time is important. The sample acquisition time, also referred to as the aperture window, needs to be as small as possible; when the MCU requests a reading, the reading needs to take place at exactly the point at which the MCU requests it – otherwise, error is introduced into the control loop which results in reduced efficiency and poor performance. With most newer SARs, sample acquisition time is not a concern, but when selecting a Delta Sigma modulator be sure to check that the sample acquisition time meets the minimum requirements of the control loop.