For dual supply digital potentiometers, if V_DD/V_SS are +2.5V/-2.5V respectively, can digital inputs be fed from a standard 3.3V CMOS logic component without logic level translation? What are the logic level thresholds when V_DD is +2.5V and V_SS is -2.5V?

For most of our digipots, you may use a standard 3.3V on the digital inputs. For AD5231/2/3/5, however, the digital input levels cannot be higher than 0.3V above V_DD or 0.3V below ground, or +2.8V and -0.3V in this case. Otherwise, the internal protection diodes may be damaged. The logical level thresholds differ from parts to parts and are also supply dependent. For example, for AD5231/2/3/5, at V_DD= +2.5V and V_SS = -2.5V the logical level high and low are +2.0V and +0.5V, respectively. Please check datasheets for more details.