Hi Thomas,
The AD7793 can latchup if overvoltages or glitches are seen on analog or digital inputs. The absolute maximum ratings list the max voltages that can be present on any analog or digital pin without causing latchup. If voltages above these absolute max ratings are seen by the ADC, internal ESD diodes will turn on and this can cause the ADC to go into an unknown state. So, any pin that may see overvoltages should have external protection (schottky diodes, for example). RC filters should be present on the analog inputs. Some filtering on the SPI lines is also useful to minimize any glitches.
Thanks and Best Regards,
Chris