SBOS531E August 2010 – June 2019 AFE031
The AFE031 includes two zero crossing detectors. Zero crossing detectors can be used to synchronize communications signals to the ac line or sources of noise. Typically, in single-phase applications, only a single zero crossing detector is used. In three-phase applications, both zero crossing detectors can be used; one component detects phase A, and one detects phase B. Phase C zero crossings can then be inferred from the data gathered from the other phases. Figure 37 shows the AFE031 configured for non-isolated zero crossing detection.
Non-isolated zero crossing waveforms are shown in Figure 38.
For maximum protection of the AFE031 against line transients, it is recommended to use Schottky diodes as indicated in Figure 37. These diodes should limit the ZC_IN pins (pins 38 and 39) to within the maximum rating of (AVDD + 0.4 V) and (AGND – 0.4 V). Some applications may require an isolated zero crossing detection circuit. With a minimal amount of components, the AFE031 can be configured for isolated zero crossing detection, as Figure 39 shows.
Isolated zero crossing waveforms are shown in Figure 40.