Question is too long. Please see the details. Thanks a lot!

[NPour.1]

Dear Sir or Madam,

I am a development electronics engineer in a company in Nuremberg, Germany.

We are at a development stage when we cannot change the circuitry without extensive tests anymore. 

In the datasheet in Table 2 on page 3 (DOC ID 2468 Rev 7, attached also here) it is stated that the Vicm must be 0 to (Vcc+ - 2)V over the whole temperature range. According to footnote 4 on page 4 "Positive excursions of input voltage may exceed the power supply level. As long as the other voltage remains within the common-mode range...".

In our circuit the supply of the comparator is connected to 3.3V. One input of the comparator swings between 0.4V and 1.9V. The other input is a constant 1.352V DC voltage. So we exceed the boundary required by the datasheet by 52mV. Will the comparator still work? How does the timing behavior of the circuit change?

You can see the comparator in our circuit in the attached file KPCL7.png.

Thanks much and yours sincerely

Naser Pour *****

[Peter BENSCH]

Yes, when considering the whole temperature range you are exceeding the limit. And exceeding the limit doesn't guarantee the datasheet values anymore - even it is just 52mV.

So trying to answer your questions (still work, timing) someone has to guarantee the function while you are outside the limits, but nobody will.

Sorry not being able to give a more pleasant answer.

/Peter

[NPour.1]

​Thanks a lot. But is there a way to find out at which temperature are we exceeding the limit? That would help us a lot. We know it is somewhere between -40°C and room temperature, and closer to -40°C because we don't exceed the boundary that much. It would be a great help to know the approximate temperature at which we exceed the limit.

[Peter BENSCH]

No, the datasheet values must be observed under the conditions specified there, i.e. Vicm=0...Vcc-2V at -40...+125°C.

One possibility could be to replace the comparator by a R2R device, but in your case, that doesn't seem to be acceptable. The same applies to changing the voltage levels to meet the requirements.

Sorry not being able to help you.

/Peter

[NPour.1]

​Thanks much anyway.