Differential ADC to measure voltages above VDD ?

[GCho.1]

When using differential ADC, it is safe to to measure voltages above VDD ?

I am trying to measure a voltage different across a current sense resistor from 12VDC power supply.

[TDK]

No, all voltages need to be within 0 and VREF+.

[S.Ma]

The purpose of differential is NOT to have a higher voltage than Vdd. It is to cancel common mode noise. This is also for the same reason that your USB cable is using a differential pair... In the digital world, you can have common voltage higher IF you typically use embedded clock 8b/10b coding AND AC coupling. This is not done on USB nor LVDS, you will find it in Display Port interface.

[GCho.1]

Hello,

Thank you for taking time to answer my question. Understood now that sampling voltage should not exceed VDD.

[Ozone]

This trouble is caused by ST's inappropriate use of terms.

A real differential ADC would have an input range spanning positive and negative voltages (e.g. -Vref ... +Vref).

But ST's differential ADC measures the difference between two ADC inputs, while both ADC input potential must be in the range 0V...Vdda.

[S.Ma]

Voltages ranges usually are specified in the electrical tables inbdatasheet. TI ADS1299 datasheet do this too.