Regarding the TS391 comparator I have a question related to the output voltage, the following is stated in the datasheet:
4 Electrical Characteristics
Under what conditions is the 700mV valid?
More information about output voltage can be found in figure below. You can see that output voltage also depends on the current. Once the output transistor cannot be hold in saturation, the output voltage will start to rise rapidly. As far as the output current is below 1mA transistor will be in saturation and Vol should be under 700mV under all operation conditions.
(extracted from ST Online Support)