LMP8645: +IN, -IN terminal input voltage range

Hi valued engineer,

Thanks for the question and using the E2E forum.

For the LMP8645, the absolute maximum voltage that can be at either of the input pins is shown in table 6.1 of the datasheet.

And as long as neither of these voltages are violated, the maximum voltage differential between the pins is 6V.

While these are the absolute maximum ratings, the safe operating region is shown in the electrical characteristics table under the CMRR spec. You can see that the 8645HV can operate from -2V to 76V, and the 8645 can operate from -2V to 42V.

As Kai points out above, this is also mentioned in section 7.1

It sounds like your application has +5V at +IN, GND at -IN , and the 5V between the pins, which is perfectly acceptable, as long as there's never greater than the 6V between +IN and -IN.

Please let us know if you have any other questions.

Louis

Yes, the Vcm voltage is the common voltage that's present at the input pins. In your example circuit, your Vcm would be the 6V at the +IN pin because the -IN would also be very close to that value (~5.9V). Here's an additional video that helps explain the Vcm.

https://training.ti.com/ti-precision-labs-op-amps-input-and-output-limitations-common-mode-voltage

The differential voltage is the voltage difference between the input pins (dropped across the Rsense). In your example, this would be 100mV (1A * 0.1ohm).

Finally, yes, the Vcm can go well above Vs, and the LMP8645 is specified up to 42V.